COVID-19 vaccines: Difference between revisions

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==Overview==
==Overview==
On December 11, 2020, the F.D.A. authorized Pfizer's vaccine for emergency use for the prevention of COVID-19. Since then, many other vaccines have been developed, such as the ones from Pfizer, Moderna, AstraZeneca, Janssen, Sinovac, Sinopharm and Gamaleya. [[Efficacy]], [[side effects]] and [[safety]] profiles vary dramatically between them, as they are produced using different mechanisms.
On December 11, 2020, the F.D.A. authorized Pfizer's vaccine for emergency use for the prevention of COVID-19. Since then, many other vaccines have been developed, such as the ones from Pfizer, Moderna, AstraZeneca, Janssen, Sinovac, Sinopharm and Gamaleya. [[Efficacy]], [[side effects]] and [[safety]] profiles vary dramatically between them, as they are produced using different strategies.
Fully vaccinated persons with a negative recent COVID-19 test are now being accepted for entering the U.S.


==Vaccines==
==Most Used Vaccines==
*All following vaccines, except for Covaxin and Sputnik are currently being accepted for entering in the U.S. for tourists.  The chosen criteria was to accept FDA and WHO-approved vaccines.
*Latest studies have shown that some vaccines have waning protection against COVID-19 infection after 5-7 months, reaching 20% efficacy. Effectiveness preventing critical disease, deaths and hospitalization has remained unaltered after 7 months.<ref name="pmid34614327">{{cite journal| author=Chemaitelly H, Tang P, Hasan MR, AlMukdad S, Yassine HM, Benslimane FM | display-authors=etal| title=Waning of BNT162b2 Vaccine Protection against SARS-CoV-2 Infection in Qatar. | journal=N Engl J Med | year= 2021 | volume=  | issue=  | pages=  | pmid=34614327 | doi=10.1056/NEJMoa2114114 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34614327  }} </ref>


===Pfizer/BioNtech Comirnaty - BNT162b2===
===Pfizer/BioNtech Comirnaty - BNT162b2===
- Mechanism of action: mRNA-based; PEGylated lipid nanoparticles vector.<br>
- Mechanism of action: mRNA-based; PEGylated lipid nanoparticles vector.<br>
It was approved for emergency use in December 11, 2020. It has been shown to have an [[efficacy]] of 95% at preventing [[COVID-19]] in persons 16 years of age or older.<ref name="pmid33301246">{{cite journal| author=Polack FP, Thomas SJ, Kitchin N, Absalon J, Gurtman A, Lockhart S | display-authors=etal| title=Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine. | journal=N Engl J Med | year= 2020 | volume= 383 | issue= 27 | pages= 2603-2615 | pmid=33301246 | doi=10.1056/NEJMoa2034577 | pmc=7745181 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33301246  }}  [https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=&cmd=prlinks&id=33524290 Review in: Ann Intern Med. 2021 Feb;174(2):JC15] </ref> Its protection against severe [[COVID-19]] was shown to be of approximately 97%. New analysis showed that after six months its [[efficacy]] fell to 84%, which is not known if this is due to the [[vaccine]] and [[immune system]] themselves of if the emergence of [[variants]] are affecting the [[efficacy]] of the [[vaccine]].  
It was approved for emergency use on December 11, 2020. It has been shown to have an [[efficacy]] of 95% at preventing [[COVID-19]] in persons 16 years of age or older.<ref name="pmid33301246">{{cite journal| author=Polack FP, Thomas SJ, Kitchin N, Absalon J, Gurtman A, Lockhart S | display-authors=etal| title=Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine. | journal=N Engl J Med | year= 2020 | volume= 383 | issue= 27 | pages= 2603-2615 | pmid=33301246 | doi=10.1056/NEJMoa2034577 | pmc=7745181 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33301246  }}  [https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=&cmd=prlinks&id=33524290 Review in: Ann Intern Med. 2021 Feb;174(2):JC15] </ref> Its protection against severe [[COVID-19]] was shown to be of approximately 97%. New analysis showed that after six months its [[efficacy]] fell to 84%, which is not known if this is due to the [[vaccine]] and [[immune system]] themselves of if the emergence of [[variants]] are affecting the [[efficacy]] of the [[vaccine]].  
As for side effects, the [[vaccine]] has been reported to cause mostly mild symptoms such as [[myalgia]], [[headaches]] and [[soreness]] in the location where it was applied. [[Allergic reactions]] have also been reported in a few patients, and they all recovered quickly after an [[epinephrine]] shot. It has been theorized that the allergic reactions were mediated by the [[PEGylated]] lipid nanoparticles in which the [[mRNA]] is stabilized. <ref name="pmid33426427">{{cite journal| author=Kleine-Tebbe J, Klimek L, Hamelmann E, Pfaar O, Taube C, Wagenmann M | display-authors=etal| title=Severe allergic reactions to the COVID-19 vaccine - statement and practical consequences. | journal=Allergol Select | year= 2021 | volume= 5 | issue=  | pages= 26-28 | pmid=33426427 | doi=10.5414/ALX02215E | pmc=7787363 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33426427  }} </ref> It has also been reported to be associated with [[myocarditis]] and [[pericarditis]], especially in young men, but the cases reported so far were mild and recovered.<ref name="pmid34268277">{{cite journal| author=Singh B, Kaur P, Cedeno L, Brahimi T, Patel P, Virk H | display-authors=etal| title=COVID-19 mRNA Vaccine and Myocarditis. | journal=Eur J Case Rep Intern Med | year= 2021 | volume= 8 | issue= 7 | pages= 002681 | pmid=34268277 | doi=10.12890/2021_002681 | pmc=8276934 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34268277  }} </ref><ref name="pmid34319393">{{cite journal| author=Tano E, San Martin S, Girgis S, Martinez-Fernandez Y, Sanchez Vegas C| title=Perimyocarditis in Adolescents After Pfizer-BioNTech COVID-19 Vaccine. | journal=J Pediatric Infect Dis Soc | year= 2021 | volume=  | issue=  | pages=  | pmid=34319393 | doi=10.1093/jpids/piab060 | pmc=8344528 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34319393  }} </ref> Efficacy against the Delta variant is of about 88%, while against the alpha variant, in the same study, it was about 93.7%.<ref name="pmid34289274">{{cite journal| author=Lopez Bernal J, Andrews N, Gower C, Gallagher E, Simmons R, Thelwall S | display-authors=etal| title=Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant. | journal=N Engl J Med | year= 2021 | volume= 385 | issue= 7 | pages= 585-594 | pmid=34289274 | doi=10.1056/NEJMoa2108891 | pmc=8314739 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34289274  }} </ref>
As for side effects, the [[vaccine]] has been reported to cause mostly mild symptoms such as [[myalgia]], [[headaches]] and [[soreness]] in the location where it was applied. [[Allergic reactions]] have also been reported in a few patients, and they all recovered quickly after an [[epinephrine]] shot. It has been theorized that the allergic reactions were mediated by the [[PEGylated]] lipid nanoparticles in which the [[mRNA]] is stabilized. <ref name="pmid33426427">{{cite journal| author=Kleine-Tebbe J, Klimek L, Hamelmann E, Pfaar O, Taube C, Wagenmann M | display-authors=etal| title=Severe allergic reactions to the COVID-19 vaccine - statement and practical consequences. | journal=Allergol Select | year= 2021 | volume= 5 | issue=  | pages= 26-28 | pmid=33426427 | doi=10.5414/ALX02215E | pmc=7787363 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33426427  }} </ref> It has also been reported to be associated with [[myocarditis]] and [[pericarditis]], especially in young men, but the cases reported so far were mild and recovered.<ref name="pmid34268277">{{cite journal| author=Singh B, Kaur P, Cedeno L, Brahimi T, Patel P, Virk H | display-authors=etal| title=COVID-19 mRNA Vaccine and Myocarditis. | journal=Eur J Case Rep Intern Med | year= 2021 | volume= 8 | issue= 7 | pages= 002681 | pmid=34268277 | doi=10.12890/2021_002681 | pmc=8276934 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34268277  }} </ref><ref name="pmid34319393">{{cite journal| author=Tano E, San Martin S, Girgis S, Martinez-Fernandez Y, Sanchez Vegas C| title=Perimyocarditis in Adolescents After Pfizer-BioNTech COVID-19 Vaccine. | journal=J Pediatric Infect Dis Soc | year= 2021 | volume=  | issue=  | pages=  | pmid=34319393 | doi=10.1093/jpids/piab060 | pmc=8344528 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34319393 }} </ref> An Israeli study found out that the most common age and gender for the occurrence of myocarditis is men between 16 and 19 years of age, after the second dose.<ref name="pmid34614328">{{cite journal| author=Mevorach D, Anis E, Cedar N, Bromberg M, Haas EJ, Nadir E | display-authors=etal| title=Myocarditis after BNT162b2 mRNA Vaccine against Covid-19 in Israel. | journal=N Engl J Med | year= 2021 | volume=  | issue=  | pages=  | pmid=34614328 | doi=10.1056/NEJMoa2109730 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34614328 }} </ref> Efficacy against the Delta variant is of about 88%, while against the alpha variant, in the same study, it was about 93.7%.<ref name="pmid34289274">{{cite journal| author=Lopez Bernal J, Andrews N, Gower C, Gallagher E, Simmons R, Thelwall S | display-authors=etal| title=Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant. | journal=N Engl J Med | year= 2021 | volume= 385 | issue= 7 | pages= 585-594 | pmid=34289274 | doi=10.1056/NEJMoa2108891 | pmc=8314739 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34289274  }} </ref> Another recent study published in NEJM showed that Pfizer's vaccine was associated with [[myocarditis]] and [[lymphadenopathy]] which occurred in 11 and 78.4 persons per 100.000 respectively. Despite that, the incidence of [[myocarditis]] in [[COVID-19]] has been shown to be much bigger. The vaccine also showed a protective effect against [[pulmonary thromboembolism]] and [[anemia]] possibly due to many undiagnosed infections among the control group which eventually complicated with such events.<ref name="pmid34432976">{{cite journal |vauthors=Barda N, Dagan N, Ben-Shlomo Y, Kepten E, Waxman J, Ohana R, Hernán MA, Lipsitch M, Kohane I, Netzer D, Reis BY, Balicer RD |title=Safety of the BNT162b2 mRNA Covid-19 Vaccine in a Nationwide Setting |journal=N Engl J Med |volume= |issue= |pages= |date=August 2021 |pmid=34432976 |doi=10.1056/NEJMoa2110475 |url=}}</ref>
*Dose regimen:
*Dose regimen:
**Application of 2 doses, spaced by 21 days between shots.
**Application of 2 doses, spaced by 21 days between shots.
**A third shot was recently recommended by the F.D.A. for immunocompromised patients.
**A third shot was recently recommended by the F.D.A. for adults 6 months after their second dose. A different israeli study showed that immunity against the delta variant of SARS-CoV-2 seemed to wane in all age groups a few months after the second dose of vaccine.<ref name="pmid34706170">{{cite journal| author=Goldberg Y, Mandel M, Bar-On YM, Bodenheimer O, Freedman L, Haas EJ | display-authors=etal| title=Waning Immunity after the BNT162b2 Vaccine in Israel. | journal=N Engl J Med | year= 2021 | volume=  | issue=  | pages=  | pmid=34706170 | doi=10.1056/NEJMoa2114228 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34706170  }} </ref> It was found that a third dose of this vaccine was associated with significantly increased antibody titers after 10 to 19 days. It also developed response in 49% of the transplant patients who previously did not have seroconversion.<ref name="pmid34739043">{{cite journal| author=Eliakim-Raz N, Leibovici-Weisman Y, Stemmer A, Ness A, Awwad M, Ghantous N | display-authors=etal| title=Antibody Titers Before and After a Third Dose of the SARS-CoV-2 BNT162b2 Vaccine in Adults Aged ≥60 Years. | journal=JAMA | year= 2021 | volume=  | issue=  | pages=  | pmid=34739043 | doi=10.1001/jama.2021.19885 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34739043  }} </ref>
*Must be kept at very low temperatures to preserve its substrate, between -80 and -60C. Undiluted vials must be kept in the refrigerator at 2 to 8C for up to 5 days, and it must not be kept at room temperature for more than 30 minutes during its administration.<ref name="pmid33629336">{{cite journal| author=Meo SA, Bukhari IA, Akram J, Meo AS, Klonoff DC| title=COVID-19 vaccines: comparison of biological, pharmacological characteristics and adverse effects of Pfizer/BioNTech and Moderna Vaccines. | journal=Eur Rev Med Pharmacol Sci | year= 2021 | volume= 25 | issue= 3 | pages= 1663-1669 | pmid=33629336 | doi=10.26355/eurrev_202102_24877 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33629336  }} </ref>
*Must be kept at very low temperatures to preserve its substrate, between -80 and -60C. Undiluted vials must be kept in the refrigerator at 2 to 8C for up to 5 days, and it must not be kept at room temperature for more than 30 minutes during its administration.<ref name="pmid33629336">{{cite journal| author=Meo SA, Bukhari IA, Akram J, Meo AS, Klonoff DC| title=COVID-19 vaccines: comparison of biological, pharmacological characteristics and adverse effects of Pfizer/BioNTech and Moderna Vaccines. | journal=Eur Rev Med Pharmacol Sci | year= 2021 | volume= 25 | issue= 3 | pages= 1663-1669 | pmid=33629336 | doi=10.26355/eurrev_202102_24877 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33629336  }} </ref>


===Moderna - mRNA-1273===
===Moderna - mRNA-1273===
- Mechanism of action: mRNA-based; lipid nanoparticles vector.<br>
- Mechanism of action: mRNA-based; [[lipid nanoparticles vector]].<br>
Approved for emergency use by the F.D.A. on December 18, 2020. The clinical trials produced by Moderna showed that its vaccine has an efficacy of 90% against symptomatic COVID-19 and 95% efficacy against severe disease after six months.  
Approved for emergency use by the F.D.A. on December 18, 2020. The clinical trials produced by Moderna showed that its vaccine has an [[efficacy]] of 90% against symptomatic [[COVID-19]] and 95% efficacy against severe disease after six months.  
Side-effects include: [[arthralgia]], [[myalgia]], [[fever]], [[chills]], [[headache]], [[nausea]] or [[induration]]/[[pain]] at application site.<ref name="pmid32991794">{{cite journal| author=Anderson EJ, Rouphael NG, Widge AT, Jackson LA, Roberts PC, Makhene M | display-authors=etal| title=Safety and Immunogenicity of SARS-CoV-2 mRNA-1273 Vaccine in Older Adults. | journal=N Engl J Med | year= 2020 | volume= 383 | issue= 25 | pages= 2427-2438 | pmid=32991794 | doi=10.1056/NEJMoa2028436 | pmc=7556339 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=32991794  }} </ref>. No allergic reaction has been described with Moderna's vaccine so far, in comparison to Pfizer's, but it has been associated with a bigger occurrence of mild side-effects in comparison to the latter.<ref name="pmid33629336">{{cite journal| author=Meo SA, Bukhari IA, Akram J, Meo AS, Klonoff DC| title=COVID-19 vaccines: comparison of biological, pharmacological characteristics and adverse effects of Pfizer/BioNTech and Moderna Vaccines. | journal=Eur Rev Med Pharmacol Sci | year= 2021 | volume= 25 | issue= 3 | pages= 1663-1669 | pmid=33629336 | doi=10.26355/eurrev_202102_24877 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33629336  }} </ref> It has also been associated with pericarditis and myocarditis, but these were mild cases, as was the case with the Pfizer's one.
Side-effects include: [[arthralgia]], [[myalgia]], [[fever]], [[chills]], [[headache]], [[nausea]] or [[induration]]/[[pain]] at application site.<ref name="pmid32991794">{{cite journal| author=Anderson EJ, Rouphael NG, Widge AT, Jackson LA, Roberts PC, Makhene M | display-authors=etal| title=Safety and Immunogenicity of SARS-CoV-2 mRNA-1273 Vaccine in Older Adults. | journal=N Engl J Med | year= 2020 | volume= 383 | issue= 25 | pages= 2427-2438 | pmid=32991794 | doi=10.1056/NEJMoa2028436 | pmc=7556339 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=32991794  }} </ref>. No [[allergic reactions]] has been described with Moderna's vaccine so far, in comparison to Pfizer's, but it has been associated with a bigger occurrence of mild [[side-effects]] in comparison to the latter.<ref name="pmid33629336">{{cite journal| author=Meo SA, Bukhari IA, Akram J, Meo AS, Klonoff DC| title=COVID-19 vaccines: comparison of biological, pharmacological characteristics and adverse effects of Pfizer/BioNTech and Moderna Vaccines. | journal=Eur Rev Med Pharmacol Sci | year= 2021 | volume= 25 | issue= 3 | pages= 1663-1669 | pmid=33629336 | doi=10.26355/eurrev_202102_24877 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33629336  }}</ref> It has also been associated with [[pericarditis]] and [[myocarditis]], but these were mild cases, as was the case with the Pfizer's one, but cases were mild and recovered.<ref name="pmid34268277">{{cite journal| author=Singh B, Kaur P, Cedeno L, Brahimi T, Patel P, Virk H | display-authors=etal| title=COVID-19 mRNA Vaccine and Myocarditis. | journal=Eur J Case Rep Intern Med | year= 2021 | volume= 8 | issue= 7 | pages= 002681 | pmid=34268277 | doi=10.12890/2021_002681 | pmc=8276934 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34268277  }} </ref><ref name="pmid34319393">{{cite journal| author=Tano E, San Martin S, Girgis S, Martinez-Fernandez Y, Sanchez Vegas C| title=Perimyocarditis in Adolescents After Pfizer-BioNTech COVID-19 Vaccine. | journal=J Pediatric Infect Dis Soc | year= 2021 | volume=  | issue=  | pages=  | pmid=34319393 | doi=10.1093/jpids/piab060 | pmc=8344528 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34319393  }} </ref> Efficacy against the Delta variant is of about 88%, while against the alpha variant, in the same study, it was about 93.7%.<ref name="pmid34289274">{{cite journal| author=Lopez Bernal J, Andrews N, Gower C, Gallagher E, Simmons R, Thelwall S | display-authors=etal| title=Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant. | journal=N Engl J Med | year= 2021 | volume= 385 | issue= 7 | pages= 585-594 | pmid=34289274 | doi=10.1056/NEJMoa2108891 | pmc=8314739 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34289274  }} </ref>
*Dose regimen:
*Dose regimen:
**Application of 2 doses, spaced by 28 days between shots.
**Application of 2 doses, spaced by 28 days between shots.
**A third shot was recently recommended by the F.D.A. for immunocompromised patients.
*Must be kept in temperatures of -25 to -15C in order to conserve its substrate. Vials can be kept in the refrigerator at 2 to 8C for up to 30 days. After first application, vial must be discarded after 6 hours.<ref name="pmid33629336">{{cite journal| author=Meo SA, Bukhari IA, Akram J, Meo AS, Klonoff DC| title=COVID-19 vaccines: comparison of biological, pharmacological characteristics and adverse effects of Pfizer/BioNTech and Moderna Vaccines. | journal=Eur Rev Med Pharmacol Sci | year= 2021 | volume= 25 | issue= 3 | pages= 1663-1669 | pmid=33629336 | doi=10.26355/eurrev_202102_24877 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33629336  }} </ref>
*Must be kept in temperatures of -25 to -15C in order to conserve its substrate. Vials can be kept in the refrigerator at 2 to 8C for up to 30 days. After first application, vial must be discarded after 6 hours.<ref name="pmid33629336">{{cite journal| author=Meo SA, Bukhari IA, Akram J, Meo AS, Klonoff DC| title=COVID-19 vaccines: comparison of biological, pharmacological characteristics and adverse effects of Pfizer/BioNTech and Moderna Vaccines. | journal=Eur Rev Med Pharmacol Sci | year= 2021 | volume= 25 | issue= 3 | pages= 1663-1669 | pmid=33629336 | doi=10.26355/eurrev_202102_24877 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33629336  }} </ref>


===Janssen - Ad26.COV2.S===
===Janssen - Ad26.COV2.S===
- Mechanism of action: adenoviral vector.<br>
- Mechanism of action: adenoviral vector Ad26.<br>
Authorized for emergency use by the F.D.A. at February 27, 2021.<ref name="pmid34260834">{{cite journal| author=Barouch DH, Stephenson KE, Sadoff J, Yu J, Chang A, Gebre M | display-authors=etal| title=Durable Humoral and Cellular Immune Responses 8 Months after Ad26.COV2.S Vaccination. | journal=N Engl J Med | year= 2021 | volume=  | issue=  | pages=  | pmid=34260834 | doi=10.1056/NEJMc2108829 | pmc=8314733 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34260834  }} </ref> According to the CDC, its efficacy has been estimated to be at approximately 67% in preventing moderate to severe COVID-19 after at least 14 days after vaccination and 66% after at least 28 days. Regarding only severe cases, its efficacy has been of approximately 77% at least 14 days after vaccination ad 85% at least 28 days after vaccination.
Authorized for emergency use by the F.D.A. on February 27, 2021.<ref name="pmid34260834">{{cite journal| author=Barouch DH, Stephenson KE, Sadoff J, Yu J, Chang A, Gebre M | display-authors=etal| title=Durable Humoral and Cellular Immune Responses 8 Months after Ad26.COV2.S Vaccination. | journal=N Engl J Med | year= 2021 | volume=  | issue=  | pages=  | pmid=34260834 | doi=10.1056/NEJMc2108829 | pmc=8314733 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34260834  }} </ref> According to the CDC, its efficacy has been estimated to be at approximately 67% in preventing moderate to severe COVID-19 after at least 14 days after vaccination and 66% after at least 28 days. Regarding only severe cases, its efficacy has been of approximately 77% at least 14 days after vaccination ad 85% at least 28 days after vaccination.
According to the CDC, the most common side effects are: [[headache]], [[fatigue]], [[nausea]], [[pain]] at the injection site and [[muscle aches]], lasting 1-2 days after injection. It was also associated with [[Guillain-Barré syndrome]] and also with [[vaccine-induced thrombocytopenia and thrombosis]].
According to the CDC, the most common side effects are: [[headache]], [[fatigue]], [[nausea]], [[pain]] at the injection site and [[muscle aches]], lasting 1-2 days after injection. It was also associated with [[Guillain-Barré syndrome]] and also with [[vaccine-induced thrombocytopenia and thrombosis]].
*Dose regimen: single dose
*Dose regimen: single dose
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===AstraZeneca/Oxford - ChAdOx1 nCoV-19===
===AstraZeneca/Oxford - ChAdOx1 nCoV-19===
- Mechanism of action: adenoviral vector.<br>
- Mechanism of action: adenoviral vector - chimpanzee adenovirus (ChAdOx).<br>
It has been associated with [[vaccine-induced immune thrombocytopenia and thrombosis]].
Not F.D.A. approved. Efficacy of preventing [[COVID-19]] infection was first estimated to be of 70.4% with a curious stark difference between two groups of patients.<ref name="pmid33306990">{{cite journal| author=Knoll MD, Wonodi C| title=Oxford-AstraZeneca COVID-19 vaccine efficacy. | journal=Lancet | year= 2021 | volume= 397 | issue= 10269 | pages= 72-74 | pmid=33306990 | doi=10.1016/S0140-6736(20)32623-4 | pmc=7832220 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33306990  }} </ref>. Efficacy against Delta variant is 67% after two doses, in comparison to an estimate of 74.5% against the alpha variant.<ref name="pmid34289274">{{cite journal| author=Lopez Bernal J, Andrews N, Gower C, Gallagher E, Simmons R, Thelwall S | display-authors=etal| title=Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant. | journal=N Engl J Med | year= 2021 | volume= 385 | issue= 7 | pages= 585-594 | pmid=34289274 | doi=10.1056/NEJMoa2108891 | pmc=8314739 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34289274  }} </ref> Patients that received first a low dose and then a standard dose had a much higher [[efficacy]] (90%) in comparison to those who got two standard doses. The trial was interrupted twice due to two cases of [[transverse myelitis]].<ref name="pmid33306990">{{cite journal| author=Knoll MD, Wonodi C| title=Oxford-AstraZeneca COVID-19 vaccine efficacy. | journal=Lancet | year= 2021 | volume= 397 | issue= 10269 | pages= 72-74 | pmid=33306990 | doi=10.1016/S0140-6736(20)32623-4 | pmc=7832220 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33306990  }} </ref>. Efficacy against Delta variant is 67% after two doses, in comparison to an estimate of 74.5% against the alpha variant.<ref name="pmid34289274">{{cite journal| author=Lopez Bernal J, Andrews N, Gower C, Gallagher E, Simmons R, Thelwall S | display-authors=etal| title=Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant. | journal=N Engl J Med | year= 2021 | volume= 385 | issue= 7 | pages= 585-594 | pmid=34289274 | doi=10.1056/NEJMoa2108891 | pmc=8314739 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34289274  }} </ref>. It was associated with [[Guillain-Barré syndrome]], which occurred very rarely, and also with [[vaccine-induced thrombocytopenia and thrombosis]]. Many studies have documented the association of this vaccine with venous thromboembolism, stating that it increases the occurrence of this event in about 20 times. Despite that, the absolute occurrence is still very rare, and researchers have concluded that the benefits far outweigh the risks.<ref name="pmid33952506">{{cite journal| author=Perera R, Fletcher J| title=Thromboembolism and the Oxford-AstraZeneca vaccine. | journal=BMJ | year= 2021 | volume= 373 | issue=  | pages= n1159 | pmid=33952506 | doi=10.1136/bmj.n1159 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33952506  }} </ref>
Efficacy against Delta variant is 67% after two doses, in comparison to 74,5% against the alpha variant.<ref name="pmid34289274">{{cite journal| author=Lopez Bernal J, Andrews N, Gower C, Gallagher E, Simmons R, Thelwall S | display-authors=etal| title=Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant. | journal=N Engl J Med | year= 2021 | volume= 385 | issue= 7 | pages= 585-594 | pmid=34289274 | doi=10.1056/NEJMoa2108891 | pmc=8314739 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34289274  }} </ref>. It was also associated with [[Guillain-Barré syndrome]] and also with [[vaccine-induced thrombocytopenia and thrombosis]].
*Dose regimen:
** Two doses spaced 8 to 12 weeks between doses.
*Must be kept at temperatures between 2 to 8C in order to conserve its substrate.


====Vaccine-induced Thrombocytopenia and Thrombosis====
====Vaccine-induced Thrombocytopenia and Thrombosis====
Line 56: Line 60:
===SinoVac - CoronaVac===
===SinoVac - CoronaVac===
- Mechanism of action: inactivated virion.<br>
- Mechanism of action: inactivated virion.<br>
Most widely used vaccine in the world against [[SARS-CoV2]], according to Airfinity. A Chilean cohort study. stated that its [[efficacy]] is at approximately 65.9% for preventing [[COVID-19]] in fully immunized patients, 87.5% for prevention of hospitalization and 90.3% for prevention of [[ICU]] admission. Its efficacy for prevention of COVID-19-related death was estimated at 86.3%.<ref name="pmid34233097">{{cite journal| author=Jara A, Undurraga EA, González C, Paredes F, Fontecilla T, Jara G | display-authors=etal| title=Effectiveness of an Inactivated SARS-CoV-2 Vaccine in Chile. | journal=N Engl J Med | year= 2021 | volume=  | issue=  | pages=  | pmid=34233097 | doi=10.1056/NEJMoa2107715 | pmc=8279092 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34233097  }} </ref>. A study performed by Butantan Institute reported an [[efficacy]] for prevention of [[COVID-19]] infection of 50.4%, 77% for prevention of mild disease and 100% [[efficacy]] on prevention of severe disease, but the numbers were not [[statistically significant]]. Despite these results, some deaths of fully vaccinated patients in the country have been reported, specially for its [[elderly]] population, which was the one that was vaccinated with CoronaVac. A non-peer reviewed study reported that it had a real-world efficacy of only 42% in the elderly population and that its [[efficacy]] decreases with age. In June, due to a reduction in its previous [[efficacy]] estimate, Chile started to give to its population older than 55 years old that were fully vaccinated with Coronavac a shot of AstraZeneca's vaccine.
Not F.D.A. approved. Most widely used vaccine in the world against [[SARS-CoV2]], according to Airfinity. A Chilean cohort study. stated that its [[efficacy]] is at approximately 65.9% for preventing [[COVID-19]] in fully immunized patients, 87.5% for prevention of hospitalization and 90.3% for prevention of [[ICU]] admission. Its efficacy for prevention of COVID-19-related death was estimated at 86.3%.<ref name="pmid34233097">{{cite journal| author=Jara A, Undurraga EA, González C, Paredes F, Fontecilla T, Jara G | display-authors=etal| title=Effectiveness of an Inactivated SARS-CoV-2 Vaccine in Chile. | journal=N Engl J Med | year= 2021 | volume=  | issue=  | pages=  | pmid=34233097 | doi=10.1056/NEJMoa2107715 | pmc=8279092 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34233097  }} </ref>. A study performed by Butantan Institute reported an [[efficacy]] for prevention of [[COVID-19]] infection of 50.4%, 77% for prevention of mild disease and 100% [[efficacy]] on prevention of severe disease, but the numbers were not [[statistically significant]]. Despite these results, some deaths of fully vaccinated patients in the country have been reported, specially for its [[elderly]] population, which was the one that was vaccinated with CoronaVac. A non-peer reviewed study reported that it had a real-world efficacy of only 42% in the elderly population and that its [[efficacy]] decreases with age. In June, due to a reduction in its previous [[efficacy]] estimate, Chile started to give to its population older than 55 years old that were fully vaccinated with Coronavac a shot of AstraZeneca's vaccine. Lastly, another Brazilian study showed that despite its efficacy, many patients still developed COVID-19 disease after the second shot and concluded that social distancing should be maintained during the vaccination campaign.<ref name="pmid34386791">{{cite journal| author=Hitchings MDT, Ranzani OT, Torres MSS, de Oliveira SB, Almiron M, Said R | display-authors=etal| title=Effectiveness of CoronaVac among healthcare workers in the setting of high SARS-CoV-2 Gamma variant transmission in Manaus, Brazil: A test-negative case-control study. | journal=Lancet Reg Health Am | year= 2021 | volume=  | issue=  | pages= 100025 | pmid=34386791 | doi=10.1016/j.lana.2021.100025 | pmc=8310555 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34386791  }} </ref>
Regarding side effects, the vaccine has a low incidence of adverse effects in comparison to the others, the most severe being an allergic reaction to a component of the vaccine that required hospitalization.<ref name="pmid34246358">{{cite journal| author=Tanriover MD, Doğanay HL, Akova M, Güner HR, Azap A, Akhan S | display-authors=etal| title=Efficacy and safety of an inactivated whole-virion SARS-CoV-2 vaccine (CoronaVac): interim results of a double-blind, randomised, placebo-controlled, phase 3 trial in Turkey. | journal=Lancet | year= 2021 | volume= 398 | issue= 10296 | pages= 213-222 | pmid=34246358 | doi=10.1016/S0140-6736(21)01429-X | pmc=8266301 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34246358  }} </ref>. Despite that, there has been case reports of [[Guillain Barré syndrome]] after its administration.
Regarding side effects, the vaccine has a low incidence of adverse effects in comparison to the others, presenting with injection site [[pain]], [[fatigue]], [[headache]], [[muscle pain]] and [[joint pain]].<ref name="pmid34203769">{{cite journal| author=Riad A, Sağıroğlu D, Üstün B, Pokorná A, Klugarová J, Attia S | display-authors=etal| title=Prevalence and Risk Factors of CoronaVac Side Effects: An Independent Cross-Sectional Study among Healthcare Workers in Turkey. | journal=J Clin Med | year= 2021 | volume= 10 | issue= 12 | pages=  | pmid=34203769 | doi=10.3390/jcm10122629 | pmc=8232682 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34203769  }} </ref> The most severe being an [[allergic reaction]] to a component of the vaccine that required hospitalization.<ref name="pmid34246358">{{cite journal| author=Tanriover MD, Doğanay HL, Akova M, Güner HR, Azap A, Akhan S | display-authors=etal| title=Efficacy and safety of an inactivated whole-virion SARS-CoV-2 vaccine (CoronaVac): interim results of a double-blind, randomised, placebo-controlled, phase 3 trial in Turkey. | journal=Lancet | year= 2021 | volume= 398 | issue= 10296 | pages= 213-222 | pmid=34246358 | doi=10.1016/S0140-6736(21)01429-X | pmc=8266301 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34246358  }} </ref>. Despite that, there are a few cases reports of [[Guillain Barré syndrome]] after its administration.
*Dose regimen:
*Dose regimen:
**Application of two doses spaced by at least 4 weeks.
**Application of two doses spaced by at least 4 weeks.


===Covaxin===
===Covaxin===
- Mechanism of action: inactivated [[virion]].<br>
Not F.D.A. approved. Its [[efficacy]] and [[safety]] was assessed in a phase I study, in which all subjects developed elevated [[antibody]] response.<ref name="pmid33636147">{{cite journal| author=| title=Correction to Lancet Infect Dis 2021; published online Jan 21. https://doi.org/10.1016/S1473-3099(20)30942-7. | journal=Lancet Infect Dis | year= 2021 | volume= 21 | issue= 4 | pages= e81 | pmid=33636147 | doi=10.1016/S1473-3099(21)00131-6 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33636147  }} </ref> Nonpublished data of ongoing phase III studies done by Bharat Biotech claimed an efficacy of 81%. It was approved for use in India before phase III studies were completed, which caused widespread criticism.
*Dose regimen:
**Application of 2 doses, spaced by 28 days between shots.
*Must be kept at temperatures between 2 to 8C in order to conserve its substrate.
===Gamaleya - Sputnik===
- Mechanism of action: heterologous recombinant [[adenovirus]] approach using adenovirus 26 and adenovirus 5 as vectors.<ref name="pmid33545098">{{cite journal| author=Jones I, Roy P| title=Sputnik V COVID-19 vaccine candidate appears safe and effective. | journal=Lancet | year= 2021 | volume= 397 | issue= 10275 | pages= 642-643 | pmid=33545098 | doi=10.1016/S0140-6736(21)00191-4 | pmc=7906719 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33545098  }} </ref><br>
This vaccine uses two different adenoviral vectors in order to expand the [[immune response]] against the [[SARS-CoV2]] [[Spike protein]], which is inserted into these vectors. It's [[efficacy]] has been estimated to be at 91.6% and disease severity was reduced after the first dose was taken.<ref name="pmid33545098">{{cite journal| author=Jones I, Roy P| title=Sputnik V COVID-19 vaccine candidate appears safe and effective. | journal=Lancet | year= 2021 | volume= 397 | issue= 10275 | pages= 642-643 | pmid=33545098 | doi=10.1016/S0140-6736(21)00191-4 | pmc=7906719 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33545098  }} </ref><ref name="pmid33545094">{{cite journal| author=Logunov DY, Dolzhikova IV, Shcheblyakov DV, Tukhvatulin AI, Zubkova OV, Dzharullaeva AS | display-authors=etal| title=Safety and efficacy of an rAd26 and rAd5 vector-based heterologous prime-boost COVID-19 vaccine: an interim analysis of a randomised controlled phase 3 trial in Russia. | journal=Lancet | year= 2021 | volume= 397 | issue= 10275 | pages= 671-681 | pmid=33545094 | doi=10.1016/S0140-6736(21)00234-8 | pmc=7852454 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33545094  }} </ref> with Gamaleya institute stating that their vaccine achieved 97.6% in real world assessment. Many criticisms were done to the vaccine's efficacy as it lacked transparency and seemed to be done at haste. Brazil's regulatory agency, ANVISA, first refused the vaccine stating that there was evidence of presence of [[adenovirus]] that "could reproduce", which would be a serious defect for the agency. It was later approved with a very restricted use and only on healthy adults. Most common side effects were: injection site reactions, [[headache]], [[asthenia]] and [[flu-like]] illness. In the same study, 122 rare serious adverse reactions were not considered to be due to the vaccination.<ref name="pmid33545094">{{cite journal| author=Logunov DY, Dolzhikova IV, Shcheblyakov DV, Tukhvatulin AI, Zubkova OV, Dzharullaeva AS | display-authors=etal| title=Safety and efficacy of an rAd26 and rAd5 vector-based heterologous prime-boost COVID-19 vaccine: an interim analysis of a randomised controlled phase 3 trial in Russia. | journal=Lancet | year= 2021 | volume= 397 | issue= 10275 | pages= 671-681 | pmid=33545094 | doi=10.1016/S0140-6736(21)00234-8 | pmc=7852454 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33545094  }} </ref> It didn't show any significant differences in sera neutralizing activity against B.1.1.7, B.1.617.3 and local russian genetic lineages B.1.1.141 , B.1.1.317, but it had a reduction of [[neutralizing activity]] against B.1.351, P.1, and B.1.617.2 of 3.1-, 2.8-, and 2.5-fold, respectively.<ref name="pmid34358195">{{cite journal| author=Gushchin VA, Dolzhikova IV, Shchetinin AM, Odintsova AS, Siniavin AE, Nikiforova MA | display-authors=etal| title=Neutralizing Activity of Sera from Sputnik V-Vaccinated People against Variants of Concern (VOC: B.1.1.7, B.1.351, P.1, B.1.617.2, B.1.617.3) and Moscow Endemic SARS-CoV-2 Variants. | journal=Vaccines (Basel) | year= 2021 | volume= 9 | issue= 7 | pages=  | pmid=34358195 | doi=10.3390/vaccines9070779 | pmc=8310330 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34358195  }} </ref>
*Dose regimen:
**Application of 2 doses, spaced by 21 days between shots.
==Promising Vaccines==
===Novavax - NVX-CoV2373===
- Mechanism of action: [[protein]]-based vaccine.


===Sputnik===
A [[phase II]] [[clinical trial]] found out that the vaccine had a 89%.7% [[efficacy]]. Most common side effect was injection-site [[tenderness]] or [[pain]] followed by [[headache]], [[fatigue]] and [[nausea]]. Later data analysis showed an efficacy of 86.3% against the B.1.1.7 (or alpha) variant and 96.4%  against non-B.1.1.7 variants.<ref name="pmid34192426">{{cite journal| author=Heath PT, Galiza EP, Baxter DN, Boffito M, Browne D, Burns F | display-authors=etal| title=Safety and Efficacy of NVX-CoV2373 Covid-19 Vaccine. | journal=N Engl J Med | year= 2021 | volume=  | issue=  | pages=  | pmid=34192426 | doi=10.1056/NEJMoa2107659 | pmc=8262625 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=34192426  }} </ref> Another study found out that the vaccine had an efficacy against B.1.351 of 51%.<ref name="pmid0.1056/NEJMoa2103055">{{cite journal| author=Ikeme MM, Adelaja AO| title=Effects of the timing of antigen stimulation on parasitaemia profile and subsequent immunodepression in an experimentally induced Trypanosoma brucei infection. | journal=Rev Elev Med Vet Pays Trop | year= 1990 | volume= 43 | issue= 3 | pages= 331-6 | pmid=0.1056/NEJMoa2103055 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=2103055  }} </ref>
It is still in development and has not been approved for use in any country.
*Dose regimen:
**Application of 2 doses, spacing yet to be determined.


==References==
==References==

Latest revision as of 21:23, 23 November 2021

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: José Eduardo Riceto Loyola Junior, M.D.[2]

Overview

On December 11, 2020, the F.D.A. authorized Pfizer's vaccine for emergency use for the prevention of COVID-19. Since then, many other vaccines have been developed, such as the ones from Pfizer, Moderna, AstraZeneca, Janssen, Sinovac, Sinopharm and Gamaleya. Efficacy, side effects and safety profiles vary dramatically between them, as they are produced using different strategies. Fully vaccinated persons with a negative recent COVID-19 test are now being accepted for entering the U.S.

Most Used Vaccines

  • All following vaccines, except for Covaxin and Sputnik are currently being accepted for entering in the U.S. for tourists. The chosen criteria was to accept FDA and WHO-approved vaccines.
  • Latest studies have shown that some vaccines have waning protection against COVID-19 infection after 5-7 months, reaching 20% efficacy. Effectiveness preventing critical disease, deaths and hospitalization has remained unaltered after 7 months.[1]

Pfizer/BioNtech Comirnaty - BNT162b2

- Mechanism of action: mRNA-based; PEGylated lipid nanoparticles vector.
It was approved for emergency use on December 11, 2020. It has been shown to have an efficacy of 95% at preventing COVID-19 in persons 16 years of age or older.[2] Its protection against severe COVID-19 was shown to be of approximately 97%. New analysis showed that after six months its efficacy fell to 84%, which is not known if this is due to the vaccine and immune system themselves of if the emergence of variants are affecting the efficacy of the vaccine. As for side effects, the vaccine has been reported to cause mostly mild symptoms such as myalgia, headaches and soreness in the location where it was applied. Allergic reactions have also been reported in a few patients, and they all recovered quickly after an epinephrine shot. It has been theorized that the allergic reactions were mediated by the PEGylated lipid nanoparticles in which the mRNA is stabilized. [3] It has also been reported to be associated with myocarditis and pericarditis, especially in young men, but the cases reported so far were mild and recovered.[4][5] An Israeli study found out that the most common age and gender for the occurrence of myocarditis is men between 16 and 19 years of age, after the second dose.[6] Efficacy against the Delta variant is of about 88%, while against the alpha variant, in the same study, it was about 93.7%.[7] Another recent study published in NEJM showed that Pfizer's vaccine was associated with myocarditis and lymphadenopathy which occurred in 11 and 78.4 persons per 100.000 respectively. Despite that, the incidence of myocarditis in COVID-19 has been shown to be much bigger. The vaccine also showed a protective effect against pulmonary thromboembolism and anemia possibly due to many undiagnosed infections among the control group which eventually complicated with such events.[8]

  • Dose regimen:
    • Application of 2 doses, spaced by 21 days between shots.
    • A third shot was recently recommended by the F.D.A. for adults 6 months after their second dose. A different israeli study showed that immunity against the delta variant of SARS-CoV-2 seemed to wane in all age groups a few months after the second dose of vaccine.[9] It was found that a third dose of this vaccine was associated with significantly increased antibody titers after 10 to 19 days. It also developed response in 49% of the transplant patients who previously did not have seroconversion.[10]
  • Must be kept at very low temperatures to preserve its substrate, between -80 and -60C. Undiluted vials must be kept in the refrigerator at 2 to 8C for up to 5 days, and it must not be kept at room temperature for more than 30 minutes during its administration.[11]

Moderna - mRNA-1273

- Mechanism of action: mRNA-based; lipid nanoparticles vector.
Approved for emergency use by the F.D.A. on December 18, 2020. The clinical trials produced by Moderna showed that its vaccine has an efficacy of 90% against symptomatic COVID-19 and 95% efficacy against severe disease after six months. Side-effects include: arthralgia, myalgia, fever, chills, headache, nausea or induration/pain at application site.[12]. No allergic reactions has been described with Moderna's vaccine so far, in comparison to Pfizer's, but it has been associated with a bigger occurrence of mild side-effects in comparison to the latter.[11] It has also been associated with pericarditis and myocarditis, but these were mild cases, as was the case with the Pfizer's one, but cases were mild and recovered.[4][5] Efficacy against the Delta variant is of about 88%, while against the alpha variant, in the same study, it was about 93.7%.[7]

  • Dose regimen:
    • Application of 2 doses, spaced by 28 days between shots.
  • Must be kept in temperatures of -25 to -15C in order to conserve its substrate. Vials can be kept in the refrigerator at 2 to 8C for up to 30 days. After first application, vial must be discarded after 6 hours.[11]

Janssen - Ad26.COV2.S

- Mechanism of action: adenoviral vector Ad26.
Authorized for emergency use by the F.D.A. on February 27, 2021.[13] According to the CDC, its efficacy has been estimated to be at approximately 67% in preventing moderate to severe COVID-19 after at least 14 days after vaccination and 66% after at least 28 days. Regarding only severe cases, its efficacy has been of approximately 77% at least 14 days after vaccination ad 85% at least 28 days after vaccination. According to the CDC, the most common side effects are: headache, fatigue, nausea, pain at the injection site and muscle aches, lasting 1-2 days after injection. It was also associated with Guillain-Barré syndrome and also with vaccine-induced thrombocytopenia and thrombosis.

  • Dose regimen: single dose
  • Must be kept at temperatures between 2 to 8C in order to conserve its substrate. Unpunctured vials may be kept between 9 to 25C for up to 12 hours.

AstraZeneca/Oxford - ChAdOx1 nCoV-19

- Mechanism of action: adenoviral vector - chimpanzee adenovirus (ChAdOx).
Not F.D.A. approved. Efficacy of preventing COVID-19 infection was first estimated to be of 70.4% with a curious stark difference between two groups of patients.[14]. Efficacy against Delta variant is 67% after two doses, in comparison to an estimate of 74.5% against the alpha variant.[7] Patients that received first a low dose and then a standard dose had a much higher efficacy (90%) in comparison to those who got two standard doses. The trial was interrupted twice due to two cases of transverse myelitis.[14]. Efficacy against Delta variant is 67% after two doses, in comparison to an estimate of 74.5% against the alpha variant.[7]. It was associated with Guillain-Barré syndrome, which occurred very rarely, and also with vaccine-induced thrombocytopenia and thrombosis. Many studies have documented the association of this vaccine with venous thromboembolism, stating that it increases the occurrence of this event in about 20 times. Despite that, the absolute occurrence is still very rare, and researchers have concluded that the benefits far outweigh the risks.[15]

  • Dose regimen:
    • Two doses spaced 8 to 12 weeks between doses.
  • Must be kept at temperatures between 2 to 8C in order to conserve its substrate.

Vaccine-induced Thrombocytopenia and Thrombosis

Diagnostic criteria - must have all four:[16][17][18]

Signs and symptoms
Headache, visual abnormalities, nausea and vomiting, back pain, leg pain and swelling, abdominal pain, shortness of breath, petechiae, bruising or bleeding.
Work-up
Imaging to screen for thrombosis + cell blood count to assess thrombocytopenia, PF4-ELISA (HIT assay), fibrinogen and D-dimer.
Treatment
If confirmed: start intravenous immune immunoglobin and nonheparin anticoagulation.

SinoVac - CoronaVac

- Mechanism of action: inactivated virion.
Not F.D.A. approved. Most widely used vaccine in the world against SARS-CoV2, according to Airfinity. A Chilean cohort study. stated that its efficacy is at approximately 65.9% for preventing COVID-19 in fully immunized patients, 87.5% for prevention of hospitalization and 90.3% for prevention of ICU admission. Its efficacy for prevention of COVID-19-related death was estimated at 86.3%.[19]. A study performed by Butantan Institute reported an efficacy for prevention of COVID-19 infection of 50.4%, 77% for prevention of mild disease and 100% efficacy on prevention of severe disease, but the numbers were not statistically significant. Despite these results, some deaths of fully vaccinated patients in the country have been reported, specially for its elderly population, which was the one that was vaccinated with CoronaVac. A non-peer reviewed study reported that it had a real-world efficacy of only 42% in the elderly population and that its efficacy decreases with age. In June, due to a reduction in its previous efficacy estimate, Chile started to give to its population older than 55 years old that were fully vaccinated with Coronavac a shot of AstraZeneca's vaccine. Lastly, another Brazilian study showed that despite its efficacy, many patients still developed COVID-19 disease after the second shot and concluded that social distancing should be maintained during the vaccination campaign.[20] Regarding side effects, the vaccine has a low incidence of adverse effects in comparison to the others, presenting with injection site pain, fatigue, headache, muscle pain and joint pain.[21] The most severe being an allergic reaction to a component of the vaccine that required hospitalization.[22]. Despite that, there are a few cases reports of Guillain Barré syndrome after its administration.

  • Dose regimen:
    • Application of two doses spaced by at least 4 weeks.

Covaxin

- Mechanism of action: inactivated virion.
Not F.D.A. approved. Its efficacy and safety was assessed in a phase I study, in which all subjects developed elevated antibody response.[23] Nonpublished data of ongoing phase III studies done by Bharat Biotech claimed an efficacy of 81%. It was approved for use in India before phase III studies were completed, which caused widespread criticism.

  • Dose regimen:
    • Application of 2 doses, spaced by 28 days between shots.
  • Must be kept at temperatures between 2 to 8C in order to conserve its substrate.

Gamaleya - Sputnik

- Mechanism of action: heterologous recombinant adenovirus approach using adenovirus 26 and adenovirus 5 as vectors.[24]
This vaccine uses two different adenoviral vectors in order to expand the immune response against the SARS-CoV2 Spike protein, which is inserted into these vectors. It's efficacy has been estimated to be at 91.6% and disease severity was reduced after the first dose was taken.[24][25] with Gamaleya institute stating that their vaccine achieved 97.6% in real world assessment. Many criticisms were done to the vaccine's efficacy as it lacked transparency and seemed to be done at haste. Brazil's regulatory agency, ANVISA, first refused the vaccine stating that there was evidence of presence of adenovirus that "could reproduce", which would be a serious defect for the agency. It was later approved with a very restricted use and only on healthy adults. Most common side effects were: injection site reactions, headache, asthenia and flu-like illness. In the same study, 122 rare serious adverse reactions were not considered to be due to the vaccination.[25] It didn't show any significant differences in sera neutralizing activity against B.1.1.7, B.1.617.3 and local russian genetic lineages B.1.1.141 , B.1.1.317, but it had a reduction of neutralizing activity against B.1.351, P.1, and B.1.617.2 of 3.1-, 2.8-, and 2.5-fold, respectively.[26]

  • Dose regimen:
    • Application of 2 doses, spaced by 21 days between shots.

Promising Vaccines

Novavax - NVX-CoV2373

- Mechanism of action: protein-based vaccine.

A phase II clinical trial found out that the vaccine had a 89%.7% efficacy. Most common side effect was injection-site tenderness or pain followed by headache, fatigue and nausea. Later data analysis showed an efficacy of 86.3% against the B.1.1.7 (or alpha) variant and 96.4% against non-B.1.1.7 variants.[27] Another study found out that the vaccine had an efficacy against B.1.351 of 51%.[28] It is still in development and has not been approved for use in any country.

  • Dose regimen:
    • Application of 2 doses, spacing yet to be determined.

References

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