As officials warn about possible summer rise in mpox, new studies show two doses of vaccine are better than one

CNN — Amid growing concern that the United States could face a rise in mpox cases this summer, three new studies show that two doses of the Jynneos mpox vaccine are much more effective than just one. “Vaccine effectiveness estimates from these studies ranged from 36% to 75% for one dose and 66% to 86% for two doses of Jynneos vaccine,” Dr. Christopher Braden, mpox response incident manager at the US Centers for Disease Control and Prevention, said in a telebriefing Thursday. Another study, published Thursday, also in the CDC’s Morbidity and Mortality Weekly Report, suggests that one dose of the Jynneos vaccine was 68.1% effective against symptomatic mpox infections but two doses was 88.5%. While the estimates of vaccine effectiveness found in this NEJM study were lower than what was found in the two other studies, Braden said that it was a strong study and “it’s advantageous to have multiple studies to understand what vaccine effectiveness really is in the population.” The data, which came from Epic’s Cosmos database, showed that the people who were diagnosed with mpox were less likely to be vaccinated than the control patients in the study. “There’s much more to unpack here,” she said, “but the vaccine remains the best chance of avoiding severe disease, including hospitalization and death, and people should plan to get vaccinated two weeks ahead of attending any major events where there is risk of exposure to mpox.” Mpox is a viral disease that spreads through close contact, and while it can infect anyone, during last year’s outbreak, infections were mostly among men who have sex with men.