JYNNEOS vaccine safety surveillance during the 2022 mpox outbreak using the Vaccine Adverse Event Reporting System (VAERS) and v-safe, United States, 2022-2023.

BACKGROUND: In response to the 2022 mpox outbreak in the United States, people with higher potential for exposure to mpox were recommended to receive two doses of the JYNNEOS vaccine. Vaccine safety was monitored using two complementary systems.

METHODS: The Vaccine Adverse Event Reporting System (VAERS) is a passive surveillance system that accepts reports of adverse events following vaccination. VAERS is capable of rapidly identifying rare adverse events and unusual reporting patterns. Medical records were requested and reviewed for adverse events of special interest, including myocarditis. Adverse event reporting rates were calculated as the number of verified adverse event cases divided by the number of JYNNEOS doses administered. V-safe for mpox was a voluntary smartphone-based vaccine safety surveillance system that sent enrolled persons text messages linked to health surveys asking about reactions and health impact events occurring after vaccination.

RESULTS: There were 1,207,056 JYNNEOS doses administered in the United States. VAERS received 1,927 reports for JYNNEOS. The myocarditis reporting rate per million doses was 2.69 after dose 1 and 8.64 after dose 2. V-safe had 213 participants complete at least one health survey. Rates of injection site and systemic reactions were similar in the first week following dose 1 and dose 2.

CONCLUSIONS: JYNNEOS vaccine safety surveillance findings from VAERS and v-safe did not identify any unexpected safety concerns. The VAERS reporting rate for myocarditis was similar to previously published population background rates.