Alliance for Pandemic Preparedness

April 6, 2021

Reactogenicity Following Receipt of mRNA-Based COVID-19 Vaccines

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  • Local and systemic adverse reactions within 7 days of vaccination were more frequently self-reported by those who received the Moderna vaccine compared to those who received the Pfizer-BioNTech vaccines. Reactions were also more frequently reported after the second dose of these vaccines. These findings are based on V-Safe, a CDC surveillance system that included 3.6 million first-dose recipients and 1.9 million second-dose recipients up to February 21, 2021. Injection site reactions within 7 days were reported by 70% and 75% of first- and second-dose recipients, while systemic reactions within 7 days of vaccination were reported by 50% and 69% of first- and second-dose recipients. The most frequently reported solicited reactions after the first dose were injection site pain (68%), fatigue (31%), and headache (26%), and for the second dose were fatigue (54%), headache (47%), and myalgia (44%). Reported reactions were highest on day 1 after vaccination and declined markedly through day 7. These findings are generally consistent with frequencies observed in clinical trials.

Chapin-Bardales et al. (Apr 5, 2021). Reactogenicity Following Receipt of mRNA-Based COVID-19 Vaccines. JAMA. https://doi.org/10.1001/jama.2021.5374