How quickly do COVID vaccines lose their effectiveness?

The rapid development and deployment of COVID vaccines has played a critical role in bringing the Pandemic under control (at least in early 2022).

But there is a disappointing factor with the current vaccines. The disappointing factor is NOT the side effects !

The disappointing factor is the loss of efficacy (protection) within a matter of months, particularly against new variants.

How quickly do the vaccines lose their effectiveness?

An Italian study published in BMJ provides some insight.

In this study involving more than 33 million people, the long term protection of Pfizer-BioNTech and Moderna vaccines was assessed.

Vaccine effectiveness against any SARS-CoV-2 infection significantly decreased from 82% to 33% at about 7 months after the second dose.

Vaccine effectiveness against severe covid-19 (admission to hospital or death) was much better though. The effectiveness decreased but to a much lesser extent, from 96% to 80%.

This Italian study confirms that a booster dose of vaccine six months after the primary vaccination cycle is the best way forward.

Reference: Effectiveness of mRNA vaccines and waning of protection against SARS-CoV-2 infection and severe covid-19 during predominant circulation of the delta variant in Italy: retrospective cohort study
BMJ 2022; 376 doi: https://doi.org/10.1136/bmj-2021-069052 (Published 10 February 2022)
Cite this as: BMJ 2022;376:e069052

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