COVID-19 mRNA vaccine safety during the first 6 months of roll-out in the USA

A primary mission of the US vaccination campaign, which began in December, 2020, following emergency use authorisation (EUA) of the BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) COVID-19 mRNA vaccines, was ensure vaccine benefit while monitoring vaccine safety.1,2 This mission was facilitated by both the enormity of the roll-out and mRNA COVID-19 vaccine distribution and the administration by the US Government of all doses, giving an unprecedented opportunity to measure vaccine safety. In The Lancet Infectious Diseases, Hannah Rosenblum and colleagues3 from the US Centers for Disease Control and Prevention report the first 6 months (Dec 14, 2020, to June 14, 2021) of safety monitoring of mRNA COVID-19 vaccines, in individuals aged at least 16 years, during which time over 50% of the eligible US population received at least one vaccine dose and more than 298 million doses were administered. Post-EUA safety data were accrued through the Vaccine Adverse Event Reporting System (VAERS), a passive and spontaneous reporting system that was established in 1990, and active surveillance through the smartphone-based system v-safe.4 V-safe was developed in 2020 to actively monitor mRNA COVID-19 vaccine safety, reactogenic symptoms, and health effects.5 Reporting rates for adverse events were calculated using the number of doses of mRNA vaccines administered during the 6 months as a denominator.6 Of the 340 522 VAERS reports submitted following both mRNA vaccines, 313 499 (92·1%) were non-serious, 246 085 (72·3%) were from female recipients, and 154 171 (45·3%) were from those aged 18–49 years.