Most mRNA COVID vaccine adverse events mild, transient

The vast majority of adverse events (92%) recorded after people received the Pfizer/BioNTech or Moderna mRNA COVID-19 vaccines during the first 6 months of the US vaccine rollout were mild and transient, according to an observational study published yesterday in The Lancet Infectious Diseases.Slightly more instances after dose 2Using the passive Vaccine Adverse Event Reporting System (VAERS) and the new active surveillance system v-safe, Centers for Disease Control and Prevention (CDC) researchers analyzed data on more than 298 million doses of the vaccines administered from Dec 14, 2020, to Jun 14, 2021.Over the study period, 298,792,852 doses of the Pfizer and Moderna COVID-19 vaccines were administered in the United States.

Of the 340,522 adverse-event reports, 92.1% were nonserious, 6.6% were serious, and 1.3% were deaths, according to VAERS. Over 80% of deaths occurred in participants 60 years and older.More than half of the 7,914,582 participants in the v-safe system reported reactions to the vaccine within the first 7 days, more often after the second dose (71.7% of 5,674,420 participants for local reactions and 70.8% for systemic events) than after the first (68.6% of 6,775,515 for local and 52.7% for systemic reactions).The most common reactions were injection-site pain (66.2% of 6,775,515 participants after dose one and 68.6% of 5,674,420 after dose two), headache (27.0% after dose one and 46.2% after dose two), most often on the day after vaccination.

Less than 1% of participants said they sought medical care (0.8% after dose one and 0.9% after dose two).The study authors noted very slight increases in anaphylaxis (severe allergic reaction, at 5.5 instances per million vaccine doses) and myopericarditis