Pfizer COVID Vaccine: How much efficacy is lost every month?

COVID vaccines lose some efficacy over time.

How much ?

Pfizer vaccine has been reported to lose, on average, about 3% efficacy every month.

An updated trial report of the Pfizer vaccine says that “ Pfizer vaccine efficacy decreased from 96% to about 84% over 4 months.

The results of this study certainly indicates that booster vaccines are needed for the winter months to prevent another wave of deaths.


BMJ News. Covid-19: Pfizer vaccine’s efficacy declined from 96% to 84% four months after second dose, company reports
BMJ 2021; 374 doi: (Published 30 July 2021)Cite this as: BMJ 2021;374:n1920

BMJ News. Covid-19: Millions could be offered booster vaccinations from September
BMJ 2021; 374 doi: (Published 02 July 2021)
Cite this as: BMJ 2021;374:n1686

Thomas SJ, Moreira ED Jr., Kitchin N, et al. Six month safety and efficacy of the BNT162b2 mRNA covid-19 vaccine.medRxiv2021 [Preprint].

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