Neutralising antibodies wane two years after mpox infection or vaccination: protection persists

Nicolò Moschetta from Vita-Salute San Raffaele University in Milan and colleagues report diminishing neutralising antibody responses to mpox after two years in a retrospective study of 90 participants (all men and all but one were MSM), 48 with previous mpox and 42 who previously received the MVA-BN mpox vaccination.

Roughly 40% were HIV positive (34/90) with median CD4 count of 741 (IQR: 562 to 1001) cells/mm3 and all >350. Viral load was undetectable in 88% (30/34).

No differences were seen in the distribution of titres at IC50 or IC90 at two years. Antibody responses based on IC90, which had been detectable after 6 months in 100% of the mpox group and 88% of the vaccine group, dropped to 31% and 17% respectively after two years.

In multivariate analyses, childhood smallpox vaccination was positively associated with higher antibody response: aOR 5.73 (95%CI: 1.31 to 22.99), p=0.02. However, the marginally higher responses in the group with previous mpox was no longer significant: aOR 2.08 (95%CI: 0.94 to 4.62), p=0.07.

No cases of new symptomatic mpox were reported in participants with previous mpox, whilst four mpox cases with mild symptoms were observed in vaccinees. This led the authors to suggest that different humoral responses or cellular responses could continue to produce more durable protection against mpox.

Moschetta N et al. A humoral dilemma: reassessing monkeypox virus neutralizing antibodies at more than two years from Mpox or MVA-BN vaccination. Journal of Infectious Diseases, 2026; jiag009.
https://doi.org/10.1093/infdis/jiag009