Study raises questions about need for mpox booster doses
Click Here to Manage Email Alerts
Key takeaways:
- Among those who received two doses of mpox vaccine but never received a smallpox vaccine in childhood, the immune response lasted less than a year.
- Currently, the CDC does not recommend booster doses.
LOS ANGELES — Neutralizing antibodies against mpox generated by the Jynneos vaccine were short lived — lasting less than a year — if patients had never received a smallpox vaccine as children, researchers said.
The findings, which were presented from the Infectious Diseases Society of America’s featured oral abstract at IDWeek, raise questions about the need for mpox booster doses for certain patients, which the CDC does not currently recommend.
Angelica C. Kottkamp, MD, an assistant professor of medicine and infectious diseases and immunology at the NYU Grossman School of Medicine, said the IgG neutralizing antibodies generated by Bavarian Nordic’s vaccine — which is approved to prevent both smallpox and mpox — are “not the only component that contributes to protection,” so the question regarding boosters is difficult to answer.
“I do think, however, that the data are intriguing, especially because older patients — immunized against smallpox during childhood — continue to have strong and highly detectable antibodies 2 years after being boosted” with the Jynneos vaccine, she told Healio.
“I think we need more data that can contribute to establishing correlates of protection, and I do agree with the need of a booster study, especially for those at high risk of severe disease, such as people with advanced HIV,” she said.
Kottkamp and colleagues conducted an observational study of almost 200 mpox vaccine recipients in New York City — a mixture of patients who had received prior smallpox vaccination and those who did not. The researchers analyzed blood samples taken from participants before vaccination and after the first and second mpox doses.
Kottkamp and colleagues published 3-month data from their study in The New England Journal of Medicine in December 2023, which showed that mpox vaccination generated strong neutralizing IgG titers in both groups, but the response in vaccine-naive individuals was not as durable, declining more quickly than in participants who had previously received a smallpox vaccine.
Data from year 2 of the study that were presented at the meeting showed a similar trajectory, with the titers continuing to diminish at a quicker rate in vaccine-naive patients. The researchers calculated that the IgG half-life was 289 days (95% CI, 239-365) for vaccine-naive patients vs. 495 days (95% CI, 408-630) for vaccine-experienced patients. They also found that the durability of neutralizing antibodies increased if patients waited longer to get their second shot. (The CDC recommends that the two doses should be given at least 28 days apart.)
The route of administration — subcutaneous or intradermal — did not have much impact on IgG titers, according to Kottkamp. During her presentation, she said this finding was reassuring because to curb the 2022 clade II mpox outbreak with a limited supply of vaccine, U.S. health officials had opted to vaccinate patients at risk for mpox infection by giving them an intradermal regimen of the shot at one-fifth the normal dose.
HIV status also had no significant impact on neutralizing IgG titers, according to Kottkamp.
The researchers used a multiplexed immunoassay to measure IgG avidity — “the quality, how good the antibodies are,” Kottkamp explained — and they found that participants who were vaccinated against smallpox had a more robust IgG response against specific mpox surface proteins vs. vaccine-naive participants.
“The good news,” Kottkamp said, was that memory B cells specific to mpox are detectable at least 1 year after vaccination regardless of prior smallpox vaccination, but more study is needed to determine if that actually correlates with protection against mpox disease.
“The most important message for clinicians is to continue to offer the vaccine to patients at risk, as this outbreak is still ongoing and there are still thousands of people at risk who have not received a dose of the mpox vaccine yet,” Kottkamp told Healio. “Keeping the conversation going is part of the protection.”
References:
- CDC. Mpox vaccine recommendations. https://www.cdc.gov/poxvirus/mpox/vaccines/vaccine-recommendations.html. Last reviewed April 22, 2024. Accessed Oct. 17, 2014.
- Kottkamp AC, et al. Abstract 229. Presented at: IDWeek; Oct. 16-19, 2024; Los Angeles.
- Kottkamp AC, et al. N Engl J Med. 2023;doi:10.1056/NEJMc2306239.
Collapse
Kottkamp AC, et al. Abstract 229. Presented at: IDWeek; Oct. 16-19, 2024; Los Angeles.
Read more about
Click Here to Manage Email Alerts