The Centers for Disease Control and Prevention’s independent advisors on Wednesday unanimously recommended administering the two-dose Jynneos vaccine to adults at risk of mpox in the event of future outbreaks, following last year’s unprecedented epidemic.
The U.S. began using the Jynneos vaccine, manufactured by the Danish company Bavarian Nordic, widely for the first time last summer after the Biden administration declared a public health emergency in response to the sudden domestic spread of mpox.
Historically, the virus has been mostly limited to West and Central Africa, but it has now spread to more than 100 countries.
“It’s important to state that an mpox outbreak will be determined by public health authorities, and a single case may be considered an mpox outbreak at the discretion of the public health authority,” said Dr. Pablo Sanchez, head of the CDC committee’s mpox workgroup.
Dr. Agam Rao, an officer in the public health service, stated that the vaccine could be deployed in the future if mpox is introduced by a traveler or through imported animals, or if a community needs to be immunized as a preventive measure due to the spread of the virus in a nearby location.
“Local health departments, state health departments, and federal authorities can all make that determination of what is considered an outbreak,” Rao said. “If there’s a single case in the United States from a traveler, then that might be enough.”
The advisors’ recommendation on Wednesday was not specific to men who have sex with men, the community most affected in the current epidemic.
Although mpox is primarily spreading through sexual contact right now, Rao noted it’s unclear how the virus would transmit in a future outbreak and which communities might be most affected.
The CDC advisors will reconvene in June to discuss using the Jynneos vaccine for children at risk of mpox in future outbreaks. The U.S. is currently offering the vaccine to adults and adolescents who are at risk in the current epidemic.
Studies found that two doses of the Jynneos vaccine were at least 66% effective in preventing mpox, with some studies showing effectiveness as high as 83%. The effectiveness of a single dose ranged from 36% to 86%, depending on the study.
It remains unclear how effective the vaccine is for individuals with weak immune systems, which is significant since 53% of people with mpox in the U.S. who disclosed their HIV status were positive.
The CDC is not currently recommending vaccination for people who have recovered from mpox because they should develop immunity from their illness, Rao said.
It is uncertain whether people may need a booster dose at some point, although a study is being conducted in the Democratic Republic of Congo to help answer that question, Rao mentioned.
Serious side effects from the vaccine were rare among adults, and none were identified among children, according to the CDC.
Seven cases of myocarditis and pericarditis, forms of heart inflammation, were reported. The CDC has not found an increased risk of heart inflammation after vaccination but has also not ruled it out.
More than 30,000 cases of mpox have been confirmed in the U.S. since May 2022. About 8% of those infected were hospitalized, and 32 died.
New cases have declined dramatically since the peak in August due to a successful vaccination campaign and greater awareness of precautionary measures.
Although the U.S. lifted the public health emergency in January, Rao emphasized that the current outbreak is not over.
Dr. Jamie Loehr, the owner of Cayuga Family Medicine in Ithaca, New York, said, “this is a common disease.”
“Even now at its lowest, we still have two cases per week, which is higher than we have had per year in the past few years,” Loehr noted.
Mpox generally isn’t fatal for most people, though it is often extremely painful, with lesions forming on sensitive areas such as the genitals.
People with severely weakened immune systems, particularly those living with HIV, face a much higher risk of severe disease and even death.
Scientists found that the fatality rate for people with advanced HIV who contracted mpox was 15% in a study of 382 cases published in The Lancet on Tuesday.
More than 1 million doses of Jynneos have been administered during the current outbreak. The Food and Drug Administration approved the Jynneos vaccine in 2019 to prevent smallpox and mpox, which are related viruses.
The World Health Organization last year changed the name of the virus, originally called monkeypox, to reduce stigma.
