Mpox vaccination in Belgium: clinical guidance for implementation readiness

BACKGROUND: Clade Ib monkeypox virus (MPXV) emerged in the Democratic Republic of Congo in 2023 with sustained sexual transmission and has since spread internationally, including to Europe. This review synthesises evidence on MVA-BN vaccine effectiveness, safety and durability to guide Belgian clinical practice. METHODS: Narrative review of MVA-BN effectiveness studies, meta-analyses, immunogenicity data and safety surveillance from the 2022-2025 clade IIb outbreak response. RESULTS: Two-dose MVA-BN effectiveness against symptomatic mpox is approximately 82% (95% CI 72-92%), although these 2022 observational estimates may be inflated by concurrent behavioural risk reduction. Pooled single-dose effectiveness is 76%, but is lower in people living with HIV (34.9%) than in HIV-negative individuals (84.1%), underlining the importance of two-dose completion in immunocompromised populations. Neutralising antibodies wane within 5 to 7 months, yet clinical protection persists through memory B-cell and T-cell responses. MVA-BN is safe in HIV infection and atopic dermatitis, with myocarditis risk below 1 per 100,000 doses; pregnancy data are limited and must be weighed against maternal and fetal risk. No direct clade I effectiveness data exist, but cross-protection is expected from epitope conservation, animal data and human evidence of protection after previous smallpox vaccination. CONCLUSIONS: Sexual health services should offer prompt vaccination to men who have sex with men with multiple partners, PrEP users, sex workers and people living with HIV, emphasising two-dose completion in immunocompromised individuals. Despite antibody waning, memory responses support durable protection against hospitalisation. Post-exposure prophylaxis is ideally given within four days, though administration up to 14 days may attenuate severity.