Alliance for Pandemic Preparedness

April 28, 2021

Vaccine Side-Effects and SARS-CoV-2 Infection after Vaccination in Users of the COVID Symptom Study App in the UK: A Prospective Observational Study

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  • SARS-CoV-2 infection rates were lower in vaccinated persons, according to reports from the COVID Symptom Study app in the UK (n=627,383). Among Pfizer-BioNTech vaccine recipients, infections were lower by 58% 12-20 days and by 72% 45-59 days after the first dose compared to frequencies in unvaccinated users, and infection rates were also lower among Oxford-AstraZeneca vaccine recipients by 39% 12-20 days and 60% 21-44 days after the first dose. Individuals with prior SARS-CoV-2 infection reported experiencing systemic side-effects 1.6 times and 2.9 times more after the first dose of the Oxford-AstraZeneca and Pfizer-BioNTech vaccines, respectively, than those without prior infection. Similarly, local side-effects were higher among individuals with prior infection. Systemic and local side-effects occurred at lower frequencies than reported in phase 3 trials. 

Menni et al. (Apr 27, 2021). Vaccine Side-Effects and SARS-CoV-2 Infection after Vaccination in Users of the COVID Symptom Study App in the UK: A Prospective Observational Study. The Lancet Infectious Diseases. https://doi.org/10.1016/S1473-3099(21)00224-3