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. 2024 Aug;29(34):2400139.
doi: 10.2807/1560-7917.ES.2024.29.34.2400139.

Effectiveness of historical smallpox vaccination against mpox clade II in men in Denmark, France, the Netherlands and Spain, 2022

Soledad Colombe  1   2 , Silvia Funke  3 , Anders Koch  4   5 , Manon Haverkate  6 , Susana Monge  7 , Anne-Sophie Barret  8 , Aisling Vaughan  1 , Susan Hahné  6 , Catharina van Ewijk  6   9 , Hanne-Dorthe Emborg  4 , Sebastian von Schreeb  10   4 , Asunción Díaz  7 , Carmen Olmedo  11 , Laura Zanetti  8 , Daniel Levy-Bruhl  8 , Luis Alves de Sousa  3 , José Hagan  1 , Nathalie Nicolay  3 , Richard Pebody  1
Affiliations

Effectiveness of historical smallpox vaccination against mpox clade II in men in Denmark, France, the Netherlands and Spain, 2022

Soledad Colombe et al. Euro Surveill. 2024 Aug.

Erratum in

  • Author's correction for Euro Surveill. 2024;29(34).
    Eurosurveillance editorial team. Eurosurveillance editorial team. Euro Surveill. 2024 Sep;29(39):2409269. doi: 10.2807/1560-7917.ES.2024.29.39.2409269. Euro Surveill. 2024. PMID: 39328160 Free PMC article. No abstract available.

Abstract

BackgroundIn 2022, a global monkeypox virus (MPXV) clade II epidemic occurred mainly among men who have sex with men. Until early 1980s, European smallpox vaccination programmes were part of worldwide smallpox eradication efforts. Having received smallpox vaccine > 20 years ago may provide some cross-protection against MPXV.AimTo assess the effectiveness of historical smallpox vaccination against laboratory-confirmed mpox in 2022 in Europe.MethodsEuropean countries with sufficient data on case vaccination status and historical smallpox vaccination coverage were included. We selected mpox cases born in these countries during the height of the national smallpox vaccination campaigns (latest 1971), male, with date of onset before 1 August 2022. We estimated vaccine effectiveness (VE) and corresponding 95% CI for each country using logistic regression as per the Farrington screening method. We calculated a pooled estimate using a random effects model.ResultsIn Denmark, France, the Netherlands and Spain, historical smallpox vaccination coverage was high (80-90%) until the end of the 1960s. VE estimates varied widely (40-80%, I2 = 82%), possibly reflecting different booster strategies. The pooled VE estimate was 70% (95% CI: 23-89%).ConclusionOur findings suggest residual cross-protection by historical smallpox vaccination against mpox caused by MPXV clade II in men with high uncertainty and heterogeneity. Individuals at high-risk of exposure should be offered mpox vaccination, following national recommendations, regardless of prior smallpox vaccine history, until further evidence becomes available. There is an urgent need to conduct similar studies in sub-Saharan countries currently affected by the MPXV clade I outbreak.

Keywords: Europe; childhood smallpox vaccination; monkeypox; mpox; screening method; vaccine effectiveness.

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Conflict of interest statement

Conflict of interest: None declared.

Figures

Figure 1
Figure 1
Estimates of smallpox vaccination coveragea by birth cohort, Denmark, France, the Netherlands, and Spain, 1900–1979
Figure 2
Figure 2
Flow of case selection for inclusion in the analysis, Denmark, France, the Netherlands and Spain
Figure 3
Figure 3
Historical smallpox vaccine effectiveness against mpox pooled over all countries, Denmarka, France, the Netherlands and Spain, March–July 2022
See this image and copyright information in PMC

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