A National Institutes of Health (NIH)-funded clinical trial of an mpox vaccine in adolescents found that it was safe and generated an antibody response equivalent to that seen in adults, according to a planned interim analysis of study data. Adolescents are among the population groups affected by mpox in the current Clade I mpox outbreak. Interim results from this trial were presented at the IDWeek2024 conference in Los Angeles.
The first human case of mpox was recorded in 1970 in the Democratic Republic of the Congo (DRC). Two types of the virus that causes mox have been identified. Clade I is endemic in Central Africa and can cause severe disease. Clade II, endemic in West Africa, caused the global mox outbreak that began in 2022 and tends to cause milder disease. People with compromised immune systems, children, and pregnant women are especially vulnerable to severe mpox, regardless of the virus clade. A large proportion of people affected by the current Clade I outbreak in the Democratic Republic of the Congo and other African countries are adolescents and children. The modified vaccinia vaccine Ankara-Bavarian Nordic (MVA-BN) is approved in several countries for the prevention of mpox and smallpox in adults, but insufficient data are available to support licensing for people under 18 years of age.
The NIH’s National Institute of Allergy and Infectious Diseases (NIAID) is sponsoring a mid-stage study in the United States to evaluate the safety and immune response generated by two doses of MVA-BN in adolescents aged 12 to 17 years, comparing the results with those of Adults from 18 to 50 years old. In a planned interim analysis, study investigators measured antibody levels two weeks after the second dose (study day 43) and monitored safety for 180 days after the second dose (study day 210). The analysis showed that the MVA-BN vaccine generated antibody levels in adolescents equivalent to those seen in adults at day 43 and found that the vaccine was well tolerated through day 210 of the study. The overall frequency of adverse events was comparable between the study groups. Reports of dizziness were more common in adolescents than in adults, but similar to the frequency of dizziness reported when other vaccines are administered in adolescents.
According to the study team, the interim data supports the safety and quality of the immune response generated by the MVA-BN vaccine in adolescents, findings relevant to the United States and other areas where mpox cases have occurred. The authors highlighted the need to evaluate the MVA-BN vaccine in younger children to expand the evidence base to all people affected by mox.
NIH thanks research sites and volunteers who participate in studies to improve the response to mpox.
For more information about this study, visit ClinicalTrials.gov and uses the identifier NCT05512949.