Waning Effectiveness of the Third Dose of the BNT162b2 mRNA COVID-19 Vaccine

The duration of protection of the third (booster) dose of the BioNTech/Pfizer BNT162b2 mRNA Coronavirus Disease 2019 vaccine has yet to be sufficiently researched, while 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 three doses of the vaccine, we found that the effectiveness in each month since vaccination decreased significantly. Compared to those vaccinated early, 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 and should prompt policy discussion as to additional booster doses and vaccine development.