Alliance for Pandemic Preparedness

April 12, 2021

Early Evidence of COVID-19 Vaccine Effectiveness within the General Population of California

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  • [Pre-print, not peer-reviewed] Fully immunized individuals (either Pfizer-BioNTech or Moderna) experienced 86% protection against SARS-CoV-2 infection, and partial protection was observed following the first dose (66%) and in the first two weeks after receipt of a second dose (78%) in a case-control study conducted from February 24 to April 7, 2021. Cases were defined by a positive SARS-CoV-2 test and controls by a negative test. Among cases (n = 325), 23 (7%) and 13 (4%) received the Pfizer-BioNTech and Moderna vaccines, respectively, and 8 (2%) were fully vaccinated while among controls 49 (19%) and 49 (19%) received Pfizer-BioNTech and Moderna, respectively; 42 (16%) were fully vaccinated. Hesitancy to receive COVID-19 vaccines (when eligible) was reported among 39% and 23% of unvaccinated participants residing in rural and urban regions, respectively. 

Andrejko et al. (Apr 10, 2021). Early Evidence of COVID-19 Vaccine Effectiveness within the General Population of California. Pre-print downloaded Apr 12 from https://doi.org/10.1101/2021.04.08.21255135