Post-exposure vaccine effectiveness and contact management in the mpox outbreak, Madrid, Spain, May to August 2022
Laura Montero Morales, José Francisco Barbas del Buey, Marcos Alonso García, Noelia Cenamor Largo, Alba Nieto Juliá, María C Vázquez Torres, Susana Jiménez Bueno, Andrés Aragón Peña, Elisa Gil Montalbán, Jesús Íñigo Martínez, María Alonso Colón, Araceli Arce Arnáez,- Virology
- Public Health, Environmental and Occupational Health
- Epidemiology
Background
Appropriate vaccination strategies have been key to controlling the outbreak of mpox outside endemic areas in 2022, yet few studies have provided information on mpox vaccine effectiveness (VE).
Aim
To assess VE after one dose of a third-generation smallpox vaccine against mpox when given as post-exposure prophylaxis (PEP) within 14 days.
Methods
A survival analysis in a prospective cohort of close contacts of laboratory-confirmed mpox cases was conducted from the beginning of the outbreak in the region of Madrid in May 2022. The study included contacts of cases in this region diagnosed between 17 May and 15 August 2022. Follow up was up to 49 days. A multivariate proportional hazard model was used to evaluate VE in the presence of confounding and interaction.
Results
Information was obtained from 484 close contacts, of which 230 were vaccinated within 14 days of exposure. Of the close contacts, 57 became ill during follow-up, eight vaccinated and 49 unvaccinated. The adjusted effectiveness of the vaccine was 88.8% (95% CI: 76.0–94.7). Among sexual contacts, VE was 93.6% (95% CI: 72.1–98.5) for non-cohabitants and 88.6% (95% CI: 66.1–96.2) for cohabitants.
Conclusion
Post-exposure prophylaxis of close contacts of mpox cases is an effective measure that can contribute to reducing the number of cases and eventually the symptoms of breakthrough infections. The continued use of PEP together with pre-exposure prophylaxis by vaccination and other population-targeted prevention measures are key factors in controlling an mpox outbreak.