Safety Monitoring of Mpox Vaccines in Adults Aged 18–64 Years during the 2022 Mpox Outbreak in the U.S.

Two vaccines (JYNNEOS; ACAM2000) were available in the United States to prevent mpox during the 2022 clade II mpox outbreak with the majority of people receiving JYNNEOS. As part of the Biologics Effectiveness and Safety (BEST) Initiative, FDA monitored the safety of JYNNEOS using three commercial health plan claims databases supplemented with local and state Immunization Information System data. We assessed vaccine uptake, described the vaccinated population, monitored rates of 11 potential adverse events (AEs) following vaccination, and compared the observed AE rates to expected background rates. There were 152,001 JYNNEOS doses administered. Of the 92,340 people receiving at least one JYNNEOS dose, most were males (93.1%), aged 25–44 years (63.3%), lived in urban areas (98.7%), and 64.2% received a second dose. AE rates following JYNNEOS doses were similar to expected background rates. Additional safety studies of larger vaccinated populations may be needed to evaluate rare AEs including myocarditis/pericarditis.