Waning effectiveness of the third dose of the BNT162b2 mRNA COVID-19 vaccine

Abstract

The duration of protection of the third (booster) dose of the BioNTech/Pfizer BNT162b2 mRNA Coronavirus Disease 2019 vaccine has been the subject of recent investigations, as global discussions around the necessity and effectiveness of a fourth dose are already underway. By conducting a retrospective study implementing a test-negative case-control design, analyzing 546,924 PCR tests performed throughout January 2022 by 389,265 persons who received at least two doses, we find that the effectiveness in each month-since-vaccination decreases significantly. Compared to those vaccinated five months prior to the outcome period, on August 2021, relative protection against infection waned from 53.4% a month after vaccination to 16.5% three months after vaccination. These results suggest that there is a significant waning of vaccine effectiveness against the Omicron variant of the third dose of the BNT162b2 vaccine within a few months after administration. Additional information could assist to comprehensively estimate the effectiveness of the three-dose-strategy.

Fig. 1. Daily SARS-Cov-2 infection and SARS-Cov-2-related hospitalization rates per 10,000 persons.

The graph exemplifies Omicron’s spread, with a rapid increase in infections and hospitalizations, peaking in mid-January.

Fig. 2. Adjusted odds ratio (left) and vaccine effectiveness (right) against SARS-CoV-2 breakthrough infection.

Left: Data are presented as adjusted OR, as a function of time in months (calendrical month) since the administration of the third dose, with error bars indicating the corresponding 95% Wald’s C.I. Right: Data are presented as adjusted VE, as a function of time in months (calendrical month) since the administration of the third dose, with error bars indicating the corresponding 95% Wald’s C.I.