Mpox antibodies wane 2 years after infection or vaccination, study finds
January 6, 2026
A new study from Italy raises important questions about the durability of antibody-based immunity to mpox after infection or vaccination. Researchers found that neutralizing antibodies often decline to low or undetectable levels within two years, even among individuals previously vaccinated with Jynneos or infected with mpox. While prior infection appeared to confer more persistent antibody responses than vaccination alone, protection likely extends beyond measurable antibodies. Cellular immunity and immune memory from earlier smallpox vaccination may still offer meaningful defense. The full study is published in The Journal of Infectious Diseases and requires institutional or paid access, limiting independent review of underlying data.
New findings from a cohort study led by researchers at Vita-Salute San Raffaele University in Milan highlight growing uncertainty around the long-term durability of antibody responses to mpox. Following 90 men for more than two years after either mpox infection or vaccination with the modified vaccinia Ankara Bavarian Nordic vaccine, investigators found that neutralizing antibodies frequently declined to low or undetectable levels in both groups.
Participants with prior mpox infection were more likely to retain detectable antibodies than vaccinated individuals, but even in this group, antibody persistence was far from universal. Antibody levels measured six months after infection or vaccination were predictive of longer-term persistence, and prior smallpox vaccination was associated with higher titers at later time points. Notably, four mpox cases occurred among vaccinated participants during follow-up, while no reinfections were observed in those with prior mpox disease.
Despite waning antibody levels, the authors caution against equating declining titers with loss of protection. They note that most mpox infections in vaccinated individuals are mild and self-limiting, suggesting that immune protection likely extends beyond neutralizing antibodies. Cellular immune responses, including T-cell mediated immunity, as well as residual immune memory from historic smallpox vaccination, may continue to play a critical role even when antibodies are no longer measurable.
These findings have implications for ongoing debates around booster dosing strategies, immune correlates of protection, and how best to assess long-term immunity in populations at risk. They also reinforce the need for more comprehensive immunological studies that integrate humoral and cellular responses rather than relying solely on antibody titers.
Importantly, the study was published in The Journal of Infectious Diseases, a subscription-based journal. Access to the full manuscript, including detailed methods and raw data, requires institutional or paid membership, which limits broader independent evaluation. As mpox continues to circulate globally, transparent and accessible immunogenicity data will be essential for informing public health policy and vaccination guidance.