As concerns mount about a large outbreak of an especially virulent form of mpox in central Africa and an uptick in U.S. cases since early last year, the mpox vaccine appears to give long-term protection, the Centers for Disease Control and Prevention reported Thursday.
In a separate report, the CDC indicated that overall new mpox infections across the U.S. have remained at a steady, low level — about 60 cases weekly, compared with 3,000 cases a week at the outbreak’s summer 2022 peak — in recent months. However, cases so far this year are elevated nationally compared with the same period in 2023 and have seen a sharp increase in New York City.
People who have gotten two doses of the Jynneos mpox vaccine are protected against infection and don’t need a booster at this time, according to the CDC.
Public health experts are concerned that the launch of the summer travel season and the upcoming LGBTQ Pride festivals in cities across the country will drive greater sexual connectivity among gay and bi men and potentially hasten mpox transmission.
Christina Hutson, chief of the CDC’s Poxvirus and Rabies Branch, and other public health experts told NBC News that this is no time for complacency about mpox (formerly called monkeypox). The various factors that likely have kept the U.S. outbreak relatively in check since late 2022 — including vaccination, infection-driven immunity, and sexual behavioral change — may be tenuous.
The mpox outbreak is “poised to return under the right conditions,” said Dr. Jeffrey Klausner, an infectious disease expert at the University of Southern California. Infections rapidly tore around the globe beginning in May 2022 and made that summer a misery for many gay and bisexual men before collapsing worldwide.
Critically, the proportion of at-risk American gay and bi men who are fully vaccinated against mpox is considered inadequate to assure long-term protection for this vulnerable population.
“Vaccination is a critical way to help protect yourself and others,” Hutson said. “It’s important that people at risk for mpox exposure who have not previously recovered from mpox — including certain gay, bisexual, and other men who have sex with men — complete the two-dose Jynneos vaccination series.”
On May 16, the CDC published an ominous report about nearly 20,000 recent cases of what is known as clade 1 of mpox that have been documented in the Democratic Republic of Congo, or DRC, since January 2023.
Concerningly, this viral clade appears to be more transmissible and to cause higher rates of severe disease and death compared with clade 2 of mpox, which drove the recent global outbreak. Five percent of those diagnosed with clade 1 in the DRC have died, compared with just 0.2% of the 96,000 people in the global clade 2 outbreak.
To date, there have been no reports of clade 1 cases outside of the handful of African nations where mpox has been endemic for decades.