The Pfizer-BioNTech BNT162b2 messenger RNA COVID-19 vaccine was found to be highly effective in preventing asymptomatic, symptomatic, and severe SARS-CoV-2 infection.
1-4 Israel was among the first countries to achieve significant nationwide vaccination coverage, leading to rapid containment of SARS-CoV-2 transmission in the community.
5,6 However, resurgence of COVID-19 cases predominated by the Delta variant was observed in June 2021
6,7 and raised concerns about waning immunity of the BNT162b2 vaccine. Declining protection of BNT162b2 against SARS-CoV-2 infection and hospitalization 4 months or more after full vaccination was demonstrated among individuals aged 60 years or older, in which those who completed a 2-dose series in March 2021 had a lower risk of SARS-CoV-2 infection compared with those vaccinated in January 2021.
7 Similarly, analysis of US data of adults without immunocompromising conditions showed a significant decline in the effectiveness of the BNT162b2 vaccine against COVID-19 hospitalizations, from 91% to 72% more than 120 days after completion of vaccination.
8 These findings are consistent with data showing time-dependent reduction in neutralizing antibody titers after vaccination.
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