A number of vaccines, including those developed by Pfizer-BioNTech, Moderna, and Oxford-AstraZeneca, have received emergency use authorization from regulatory bodies in different countries. The spread of coronavirus disease 2019 (COVID-19) has ravaged global health and suppressed economic activity despite the range of mitigation measures implemented by countries worldwide. Our findings underscore the importance of quantifying the characteristics and durability of vaccine-induced protection after the first dose in order to determine the optimal time interval between the two doses. However, there was no clear advantage of delaying the second dose with Pfizer-BioNTech vaccines in reducing infections, unless the efficacy of the first dose did not wane over time.
Pfizer-BioNTech vaccines also averted an additional 0.61 (95% CrI: 0.37 – 0.89) hospitalizations and 0.31 (95% CrI: 0.23 – 0.45) deaths per 10,000 population in a 9-week delayed second dose strategy compared to the 3-week recommended schedule between doses. Our results show that for Moderna vaccines, a delay of at least 9 weeks could maximize vaccination program effectiveness and avert at least an additional 17.3 (95% CrI: 7.8 – 29.7) infections, 0.71 (95% CrI: 0.52 – 0.97) hospitalizations, and 0.34 (95% CrI: 0.25 – 0.44) deaths per 10,000 population compared to the recommended 4-week interval between the two doses. We developed an agent-based model of COVID-19 transmission to compare the impact of these two vaccination strategies, while varying the temporal waning of vaccine efficacy following the first dose and the level of pre-existing immunity in the population.
#PFIZER 2ND DOSE TIMING SERIES#
Constraints in vaccine supply and distribution capacity, together with a deadly wave of COVID-19 from November 2020 to January 2021 and the emergence of highly contagious SARS-CoV-2 variants, sparked a policy debate on whether to vaccinate more individuals with the first dose of available vaccines and delay the second dose, or to continue with the recommended two-dose series as tested in clinical trials. Two of the COVID-19 vaccines currently approved in the United States require two doses, administered three to four weeks apart.
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