With the clade 1 outbreak of mpox (formerly monkeypox) raging through the Congo and other countries in Central Africa, younger people have become markedly vulnerable to infection.
While Bavarian Nordic’s vaccine Jynneos is approved in several countries to prevent mpox and smallpox infections in adults, there has been a lack of data to support its approval in adolescents. But that is beginning to change as interim results of a trial of Jynneos in teenagers indicate that it is safe and elicits a comparable immune response as seen in adults.
Earlier this week, based on results from a 2023 study, the World Health Organization announced the prequalification of Jynneos for adolescents ages 12 to 17.
The most recent study, which is sponsored by the National Institute of Allergy and Infectious Diseases (NAID) and conducted by the National Institutes of Health (NIH), has demonstrated that Jynneos triggers an immune response in subjects between the ages of 12 and 17 that’s comparable responses seen by adults ages 18 to 50. The data were presented at the IDWeek2024 conference in Los Angeles.
In the trial, which includes 315 adolescents in the United States who received the standard two doses of Jynneos four weeks apart, investigators measured antibody levels two weeks after the second dose and monitored patients for six months after full vaccination. Also participating the study is a comparison group of 135 adults ages 18 to 50.
In addition to finding that the antibody levels were comparable between the groups, investigators discovered no difference in the frequency of adverse side effects. While reports of dizziness were more common in adolescents than adults, the difference in frequency matched that seen in other vaccines administered in adolescents and adults.
While authors of the study reported that the interim data “support the safety and quality of the immune response generated” by Jynneos, they also underscored the need to evaluate the subcutaneous shot in younger children to extend the evidence base to all of those affected by mpox.
In August 2024, a clade I outbreak in Africa prompted the World Health Organization (WHO) to declare a public health emergency of international concern. A clade II virus caused a global mpox outbreak in 2022. Clade II mpox is still circulating in several countries, but at much lower levels than during the first year of the outbreak. Clade II typically results in milder illness, but both types can evolve into life-threatening illness, especially for pregnant women, children and those with compromised immune systems.
In the WHO’s most recent update earlier this month, mpox cases were recorded in 16 countries in Africa within the last six weeks. The country most affected has been the Congo, with 6169 cases this year, including 25 deaths.
While BN was previously the lone drugmaker with an approved mpox vaccine, it’s now joined by Emergent BioSolutions, which snagged an expanded green light for its smallpox vaccine ACAM2000 in late August. The FDA specifically signed off on the shot as a preventative for people at high risk of mpox infection, leveraging an animal study and previously available human safety data.
Last month, an investigational mpox shot from Moderna topped Jynneos at preventing severe disease and reducing virus levels in monkeys. In 2019, the FDA approved Jynneos to prevent infection from smallpox and mpox in adults.