Mpox JYNNEOS vaccine gets new attention as CDC warns of possible resurgence : Shots

A sign for monkeypox vaccinations is shown at a vaccination site in Miami Beach, Fla.

Lynne Sladky/AP

When the JYNNEOS vaccine for mpox rolled out last summer, health officials believed it would work. It was an educated guess, at the height of a public health emergency, based mostly on data from animal studies.

Now, after 1.2 million doses have been given in the U.S., the Centers for Disease Control and Prevention has real-world evidence that the mpox vaccines are working to prevent disease.

Three new studies show that two doses of the JYNNEOS vaccine are somewhere between 66% and 86% effective at preventing mpox among people at risk. The research was published on Thursday in the New England Journal of Medicine and the CDC’s Morbidity and Mortality Weekly,

“Two doses of vaccine offer the best protection against mpox disease,” says Leora Feldstein, an epidemiologist at the CDC. “We really recommend staying up to date on vaccination going into the summer and into pride season.”

The new data come as health officials are working to stave off a possible summer wave of mpox.

The CDC’s concern about a resurgence of mpox is based on a recent cluster of cases found in Chicago. In the past month, 21 people there were diagnosed with mpox, according to Dr. Demetre Daskalakis, deputy director for the White House National Monkeypox Response, who spoke at a press briefing on Thursday.

The cluster of cases breaks a three-month streak where almost no cases were found in Chicago. Daily cases remain low across the U.S. Many of the people who caught mpox in Chicago had been fully vaccinated; none were hospitalized.

“Even if it doesn’t prevent infection…vaccination makes getting and spreading impacts less…