Smallpox vaccination in childhood could offer protection against monkeypox clade II viruses, study finds

A examine by co-authors from the ECDC, WHO and nationwide public well being institutes in 4 European international locations, and revealed in Eurosurveillance, has discovered that prior smallpox vaccination in childhood may shield in opposition to infections attributable to monkeypox virus (MPXV) clade II in males. However, the estimated diploma of safety assorted amongst international locations, highlighting the necessity for additional analysis to validate the examine findings.

In mild of the 2022–2023 outbreak of mpox in Europe that primarily affected sure teams with high-risk habits amongst males who’ve intercourse with males, the examine sought to find out the effectiveness of historic smallpox vaccination throughout childhood in opposition to laboratory-confirmed mpox, to tell vaccination efforts.

Case-based surveillance information had been chosen from international locations that collected info on prior smallpox vaccination standing of mpox instances and had accessible information on historic smallpox vaccination protection, specifically Denmark, France (mainland solely), the Netherlands (mainland solely) and Spain.

The examine analyzed mpox instances born in these international locations throughout the peak of nationwide smallpox vaccination campaigns (newest in 1971). Too few mpox instances in females had been reported to regulate for intercourse within the evaluation, so solely instances recorded as male had been included.

Vaccine effectiveness and corresponding 95% confidence intervals (CI) for every nation had been then estimated utilizing logistic regression as per the Farrington screening methodology. A pooled estimate was then calculated utilizing a random results mannequin.

Results and public well being implications

Estimated historic smallpox protection was excessive (80–90%) throughout all international locations till the tip of the Nineteen Sixties, dropping off significantly over the past 10 years of vaccination applications.

Estimates of vaccine effectiveness of prior smallpox vaccination in opposition to mpox attributable to MPXV clade II assorted broadly between international locations, starting from 42% within the Netherlands to 84% in Spain, presumably reflecting completely different booster methods. The pooled vaccine effectiveness estimate was 70% with a large 95% confidence interval of 23–89%, indicating a excessive stage of uncertainty.

The examine findings recommend that historic childhood smallpox vaccination in a European setting may shield two-thirds of males in opposition to mpox attributable to MPXV clade II. However, there was important uncertainty within the outcomes and variation between international locations. The outcomes of this examine are due to this fact not ample to help differential smallpox vaccination to guard in opposition to mpox primarily based on historic smallpox vaccination standing or age.

The authors advocate that people with a excessive threat of publicity be provided mpox vaccination, no matter vaccination historical past. With the latest surge of clade Ib mpox instances in a number of international locations in central and East Africa, there’s an pressing must conduct comparable research on the effectiveness of the smallpox vaccine in opposition to the newest circulating clade.

Provided by
European Centre for Disease Prevention and Control (ECDC)