Reduction in the risk of mpox infection after MVA-BN vaccination in individuals on HIV pre-exposure prophylaxis: a Spanish cohort study

Abstract

Objectives: To assess the effectiveness of at least one-dose of the Modified Vaccinia Ankara-Bavaria Nordic (MVA-BN) smallpox vaccine, administered pre-exposure, against mpox virus (MPXV) infection in persons receiving pre-exposure prophylaxis for HIV (HIV-PrEP). Design: Retrospective cohort, constructed by deterministic linkage of electronic health records. Setting: 15 of 19 regions in Spain (>95% population), between July 12 and December 12, 2022 Participants: Men >=18 years, receiving HIV-PrEP as of July 12 and with no previous MPXV infection or vaccination against mpox. Interventions: On each day, we matched individuals receiving a first dose of MVA-BN vaccine pre-exposure and unvaccinated controls of the same age (minus/plus 5 years) and region. Main outcome measures: We estimated the risk of laboratory-confirmed infection with MPXV using a Kaplan-Meier estimator and calculated risk ratios (RR) and vaccine effectiveness (VE=1-RR). Results: We included 5,660 matched pairs, with a median follow-up of 62 days (interquartile range 24-97). Mpox cumulative incidence was 5.6 per 1,000 (25 cases) in unvaccinated and 3.5 per 1,000 (18 cases) in vaccinated; last case occurred at 63 and 17 days after enrolment, respectively. No effect was found during days 0-6 post-vaccination (VE -38.3; 95% confidence interval (95%CI): -332.7; 46.4), but VE was 65% in ≥7 days (95%CI 22.9; 88.0) and 79% in ≥14 days (95%CI 33.3; 100.0) after vaccination. Conclusion: At least one dose of MVA-BN vaccine offered protection against mpox in a most-at-risk population. Because the incidence of mpox was decreasing shortly after the vaccination campaign began, we can only assess its effectiveness shortly after vaccination. Further studies need to assess the VE of a second dose and the duration of protection over time.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

No funding was obtained for this study

Author Declarations

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

This study was approved by the Research Ethics Committee at the Institute of Health Carlos III (approval no. CEI PI 92_2022) and by the Research with Drugs Ethics Committee at the Community of Madrid (approval no. EV_MPOX-001)

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

Data Availability

The data that support the findings of this study will not be made publicly available due to data protection. Further information including the procedures for obtaining and accessing data could be obtained upon request from the corresponding author.

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