Since March 1, 2023, more than 30,000 cases of mpox (formerly monkeypox) have been reported in the United States. This virus disproportionately affects transgender persons as well as gay and bisexual men. In 2019, the live, non-replicating smallpox vaccine (JYNNEOS®) was approved for subcutaneous inoculation to prevent mpox. Three years later, in August 2022, the vaccine was also licensed for intradermal use. Effectiveness data for either route of administration have been limited.

Recently, researchers from the Centers for Disease Control and Prevention (CDC) studied the effectiveness of mpox vaccine in those infected (Deputy NP, Deckert J, Chard AN, et al. “Vaccine effectiveness of JYNNEOS against mpox disease in the United States.” N Engl J of Med 2023, June 29;388(26):2434-2443). Among 2,193 case patients and 8,319 control patients, vaccine effectiveness was 66% after two doses and 36% after one dose. The authors concluded that “… JYNNEOS vaccine was effective in preventing mpox disease, and a two-dose series appeared to provide better protection” (p. 2434).

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