Loading...
The repurposed JYNNEOS vaccine (originally developed for smallpox) has been shown to be highly effective in preventing monkeypox (mpox; NEJM JW Infect Dis Jun 8 2023). However, in a recent mpox outbreak in Chicago, a relatively high proportion of patients had been either fully or partially vaccinated with JYNNEOS or another anti-mpox vaccine (ACAM2000).
During April 17–May 5, 2023 (following a 2-month period when only 1 mpox case had been reported), 13 mpox cases were reported in Chicago. More than 69% of this cluster had received 2 doses of JYNNEOS or 1 dose of ACAM2000 >2 weeks before illness — a percentage higher than expected based on previous vaccination effectiveness data. Possible causes of high failure likelihood include lapses in va…