Safety Monitoring of mRNA Vaccines Administered During the Initial 6 Months of the U.S. COVID-19 Vaccination Program: Reports to Vaccine Adverse Events Reporting System (VAERS) and v-safe

Background: In December 2020, two mRNA-based COVID-19 vaccines were authorized for use in the United States. Vaccine safety was monitored using the Vaccine Adverse Event Reporting System (VAERS), a passive surveillance system, and v-safe, an active surveillance system. Methods: VAERS and v-safe data during December 14, 2020-June 14, 2021 were analyzed. VAERS reports were categorized as non-serious, serious, or death; reporting rates were calculated. Rates of reported deaths were compared to expected mortality rates by age. Proportions of v-safe participants reporting local and systemic reactions or health impacts the week following doses 1 and 2 were determined. Findings: During the analytic period, 298,792,852 doses of mRNA vaccines were administered in the United States. VAERS processed 340,522 reports; 92.1% were non-serious; 6.6%, serious, non-death; and 1.3%, death. Over half of 7,914,583 v-safe participants self-reported local and systemic reactogenicity, more frequently after dose 2. Injection-site pain, fatigue, and headache were commonly reported during days 0-7 following vaccination. Reactogenicity was reported most frequently one day after vaccination; most reactions were mild. More reports of being unable to work or do normal activities occurred after dose 2 (32.1%) than dose 1 (11.9%); <1% of participants reported seeking medical care after vaccination. Rates of deaths reported to VAERS were lower than expected background rates by age group. Interpretation: Safety data from >298 million doses of mRNA COVID-19 vaccine administered in the first 6 months of the U.S. vaccination program show the majority of reported adverse events were mild and short in duration.