mRNA vaccine (BNT166a) for mpox and smallpox prevention in adults in Africa

Safety, Reactogenicity, and Immunogenicity of an Mpox mRNA Vaccine Candidate, BNT166a, in Healthy Participants Aged 18 Years and Older in African Countries: A Randomized, Double-blind, Placebo-controlled Phase II Trial

Phase 2 Interventional BioNTech SE · NCT07379580

This tests whether two doses of the mRNA vaccine BNT166a are safe and produce an immune response in healthy adults in Africa, including people who have or have not had prior smallpox or mpox exposure.

Quick facts

PhasePhase 2
Study typeInterventional
Enrollment310 (estimated)
Ages18 Years to 64 Years
SexAll
SponsorBioNTech SE Industry-sponsored
Locations6 sites (Kinshasa and 5 other locations)
Trial IDNCT07379580 on ClinicalTrials.gov

What this trial studies

This randomized, double-blind, placebo-controlled Phase 2 trial gives participants two doses of the mRNA vaccine BNT166a or placebo at least 28 days apart and follows them for about 14 months. Participants are grouped into two cohorts: orthopoxvirus-naïve adults aged 18–45 and orthopoxvirus-experienced adults aged 18–64. The study measures safety, local and systemic reactogenicity, and immune responses after one and two doses. Data will compare vaccine versus placebo within each cohort to characterize tolerability and antibody responses.

Who should consider this trial

Good fit: Healthy adults able to attend one of the African study sites who meet the age and exposure criteria—either 18–45 years with no prior mpox/smallpox exposure or 18–64 years with prior mpox/smallpox infection or vaccination at least two years earlier—are ideal candidates.

Not a fit: People with recent mpox exposure, mpox infection or vaccination within the past two years, or with contraindications to mRNA COVID-19 vaccines are unlikely to benefit from participating.

Why it matters

Potential benefit: If successful, the vaccine could provide a new mRNA-based option to protect against mpox and boost orthopoxvirus immunity.

How similar studies have performed: The mRNA vaccine platform has proven highly effective for COVID-19 and other candidates, but mRNA vaccines specifically targeting mpox are relatively new with limited human data to date.

Eligibility criteria

Show full inclusion / exclusion criteria
Key Inclusion Criteria (applicable to all participants unless otherwise specified):

* Are male or female individuals ≥18 years of age at the time of giving informed consent:

  * Cohort 1: ≥18 to ≤45 years of age
  * Cohort 2: ≥18 to ≤64 years of age
* Cohort 1: Participants must be Orthopoxvirus-naïve (have no history of smallpox or mpox vaccination or mpox infection).
* Cohort 2: Participants must be Orthopoxvirus-experienced (have evidence of mpox or smallpox vaccination or mpox infection at least 2 years prior to consent).

Key Exclusion Criteria (applicable to all participants unless otherwise specified):

* Have had recent exposure to mpox (defined as close contact with a probable or confirmed case of mpox within the past 28 days, or have evidence of mpox infection or mpox vaccination within 2 years prior to consent).
* Have a contraindication, warning and/or precaution to vaccination with a messenger ribonucleic acid (mRNA) Coronavirus disease 2019 (COVID-19) vaccine as specified in the Summary of Product Characteristics for BNT162b2 (COMIRNATY United States Prescribing Information/European Union Summary of Product Characteristics) and BNT166 Investigator Brochure.
* Have a history of allergies, hypersensitivities, or intolerance to the study treatments including any excipients thereof.
* Have a current or history of cardiovascular diseases, e.g., myocarditis, pericarditis, myocardial infarction, congestive heart failure, cardiomyopathy, or clinically significant arrhythmias.
* Have any known bleeding diathesis or condition associated with prolonged bleeding that would, in the opinion of the investigator, contraindicate intramuscular injection.
* Have a body mass index ≤18.5 kg/m\^2 or ≥35 kg/m\^2.

NOTE: Other protocol defined Inclusion/Exclusion criteria apply.

Where this trial is running

Kinshasa and 5 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions MpoxSmallpoxOrthopoxvirus InfectionMonkeypox virusActive immunizationRibonucleic acid vaccine
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.