MVA-BN third-dose 5 years after primary; Democratic Republic of the Congo

BACKGROUND The expanding mpox outbreak in Africa and travel-associated cases in other continents have sparked efforts to expand vaccination. In this study and the accompanying report (Minhaj et al.), we assess the safety and long-term immunological response of MVA-BN vaccination.

In 2022, five years after the primary MVA-BN series, a third (booster) dose was administered to healthcare workers in the Democratic Republic of the Congo (DRC). Adverse events were recorded on days 0, 7, and 14, and antibody response measured on days 0, 7, 14, and 545 following the third dose. Study documentation and surveillance records were examined to identify possible infections following the primary series.

Antibody kinetics indicative of an anamnestic response, with a rapid and massive increase in anti-Orthopoxvirus (OPXV)-specific IgG but not IgM, and a nearly 90-fold rise in OPXV-neutralizing antibody titers were observed by day 14. Anamnestic response was observed in all participants irrespective of their seropositivity at the time of booster vaccination with enhanced antibody levels through day 545. In comparison to primary vaccination, third dose participants had 4.2 greater odds of experiencing local reactogenicity, but no difference in systemic adverse events through day 7 post-vaccination. Finally, in five years following the primary series, only one confirmed case of mpox has been identified.

MVA-BN vaccination induces sustained immunological memory after primary vaccination observed by rapid anamnestic response up to five years post-vaccination. Booster vaccination had increased reactogenicity compared to primary vaccination but enhances antibody durability. Competing Interest Statement The authors have declared no competing interest. Clinical Trial NCT02977715 Funding Statement This work was funded by the CDC. No other external funding was received. 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: The CDC and Kinshasa School of Public Health Institutional Review Boards gave ethical approval for this work I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the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 Footnotes The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention. Data Availability All data produced in the present study are available upon reasonable request to the authors