Vaccinated at Higher Risk of Serious Adverse Events: Reanalysis of Original Trial Data

Syringes and vials of the Pfizer-BioNTech COVID-19 vaccine are prepared to be administered at a drive-up vaccination site from Renown Health in Reno, Nev., on Dec. 17, 2020. Patrick T. Fallon/AFP via Getty Images

A secondary analysis of the data from the original clinical trials for the Pfizer and Moderna COVID-19 vaccines has found that the vaccinated arms were at higher risk of serious adverse events than the placebo arms.

Pfizer trial participants who received a vaccine were 36 percent more at risk of a serious adverse event, while Moderna trial participants who received a vaccine were six percent more at risk, according to the analysis, which was published after peer review in the journal Vaccine on Aug. 31.