The effect of smallpox and BCG vaccination on the risk of HIV-1 infection in Guinea-Bissau and Denmark | Open Forum Infectious Diseases | Oxford Academic

The live smallpox and BCG vaccinations have been associated with better adult survival in both Guinea-Bissau and Denmark. In Guinea-Bissau, HIV-1 became an important cause of death after smallpox vaccination was phased out globally in 1980. We hypothesised that smallpox and BCG vaccinations were associated with a lower prevalence of HIV-1 infection, and tested this hypothesis both in Guinea-Bissau and in Denmark.

We conducted two studies, a cross-sectional study of HIV infection and vaccination scars in Guinea-Bissau including 1,751 individuals, and a case-base study with a background population of 46,239 individuals in Denmark. In Guinea-Bissau, HIV-1 transmission is almost exclusively sexually transmitted, in Denmark we excluded intravenous drug users. Data was analysed using logistic regression.

BCG and/or smallpox vaccination compared with neither of these vaccines was associated with an adjusted odds ratio (aOR) for HIV-1 of 0.62 (95% confidence interval (CI) 0.36-1.07) in Guinea-Bissau and 0.70 (95%CI 0.43-1.15) in Denmark. Combining results from both settings in a meta-analysis gave an aOR of 0.66 (95%CI 0.46-0.96). Data from Guinea-Bissau indicated a stronger effect of multiple smallpox vaccination scars (aOR of 0.27 (95%CI 0.10-0.75); women: 0.18 (95%CI 0.05-0.64), men: 0.52 (95%CI 0.12-2.33), sex-differential effect, p-value = 0.29).

The studies from Guinea-Bissau and Denmark, two very different settings, both suggest that the BCG and smallpox vaccines could be associated with a decreased risk of sexually transmitted HIV-1. It might be informative to pursue this observation and explore possible protective mechanisms as part of the search for an HIV-1 vaccine."

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