MODIFIED VACCINIA ANKARA – BAVARIAN NORDIC LIVE VIRUS for Mpox (monkeypox)

Inclusion criteria

• {"criterion_text":"- Aged 18 years and over, at the time of informed consent\n- Capable of giving personal signed informed consent, which includes compliance with the requirements listed in this protocol\n- Born after 1974 and having received two doses of MVA-BN vaccination regimen at least one year after the second dose before being recruited\n- Healthy participants who are determined by medical history and clinical judgment of the investigator to be eligible for inclusion in the study. Healthy participants with pre-existing stable disease, defined as disease not requiring significant change in therapy or hospitalization for worsening disease during the 6 weeks before enrolment, can be included\n- Participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, and other study procedures\n- Participants of childbearing potential (i.e. have a uterus and are neither surgically sterilized nor post-menopausal) must not be pregnant or breast-feeding. They should agree to a pregnancy test and use adequate contraception at least up to four weeks following the third vaccination of MVA-BN."}

Exclusion criteria

• {"criterion_text":"- History of previous smallpox vaccination or evidence of a vaccinia scar\n- Planned pregnancy within four weeks after the injection (participants of childbearing potential)\n- Participation in other studies involving study intervention within 28 days prior to study entry and/or during study participation (i.e. 7 months)\n- Previous clinical or microbiological diagnosis of mpox\n- History of severe adverse reaction associated with a vaccine and/or severe allergic reaction (e.g., anaphylaxis) to any component of the study intervention (chicken protein, benzonase, gentamicin and ciprofloxacin)\n- Persons living with HIV and CD4-count <350 and/or detectable viral load at their most recent follow up at the outpatient clinic\n- Immunosuppressed individuals with known or suspected immunodeficiency, as determined by history\n- Individuals with a history of autoimmune disease or an active autoimmune disease, except for type 1 diabetes mellitus and auto-immune diseases of the skin or thyroid that do not require systemic immunosuppression\n- Receipt of systemic corticosteroids withing one month before the study intervention\n- Any physical or psychiatric illness or conditions that could threaten or compromise the health of the participant during the study, influence their ability to participate in the trial or interfere with the interpretation of the study results, as determined by the trial physician\n- Pregnancy or breastfeeding (participants of childbearing potential)"}

Primary endpoints

• {"endpoint_text":"- Geometric mean concentrations (GMC) of VACV-specific antibodies (D0, D14)","definition_or_measurement_approach":"GMC of VACV-specific antibodies measured at baseline (D0) and 14 days after booster vaccination (D14)."}

Secondary endpoints

• {"endpoint_text":"- GMC of antibodies against VACV (M6), MVA-BN and MPXV (D0, D14 and M6)","definition_or_measurement_approach":"GMC measured at D0, D14 and month 6 (M6) for VACV (M6), MVA-BN and MPXV."}
• {"endpoint_text":"- Seroconversion for neutralizing antibodies in a subgroup of participants to VACV, MVA-BN, and MPXV (D0, D14, M6)","definition_or_measurement_approach":"Assessment of seroconversion for neutralizing antibodies at D0, D14 and M6 in a subgroup."}
• {"endpoint_text":"- GMT for neutralizing antibodies in a subgroup of participants to VACV, MVA-BN, and MPXV (D0, D14, M6)","definition_or_measurement_approach":"Geometric mean titres for neutralizing antibodies measured at D0, D14 and M6 in a subgroup."}
• {"endpoint_text":"- Percentages of MPXV- and VACV-specific T cells in a subgroup of participants","definition_or_measurement_approach":"Flow cytometry or other cellular assays to quantify MPXV- and VACV-specific T cell percentages in a subgroup (timepoints as per protocol)."}
• {"endpoint_text":"- Number of spot forming unit per million cells (IFN-g ELISpot) upon stimulation with peptide generated using VACV sequences","definition_or_measurement_approach":"IFN-γ ELISpot: spot forming units per million cells after stimulation with VACV-derived peptides."}
• {"endpoint_text":"- Percentages of activated T cells following peptide stimulation","definition_or_measurement_approach":"Percentages of activated T cells measured after peptide stimulation (assay/timepoints per protocol)."}
• {"endpoint_text":"- Self-reported local and systemic reactions over a 7-day period, or until symptom remission, using an (electronical) diary and control visits at day 14 and month 6 months after booster vaccination","definition_or_measurement_approach":"Participants report local and systemic reactions in an electronic diary for 7 days or until symptom remission; follow-up visits at day 14 and month 6."}
• {"endpoint_text":"- Adverse events (AEs) until one week after vaccination or until symptom remission, using an (electronical) diary and control visits at day 14 and month 6 months after booster vaccination","definition_or_measurement_approach":"AE collection via electronic diary for one week or until remission; assessed at day 14 and month 6 visits."}
• {"endpoint_text":"- Serious AEs (SAEs) until six months after vaccination","definition_or_measurement_approach":"Recording of SAEs through six months post-vaccination per standard safety reporting."}

Netherlands

Latest Decision Or Authorization Date

06-03-2026

Number Of Sites

3

Number Of Participants

220

Primary sponsor

Full Name

Academisch Ziekenhuis Leiden

Organisation Type

Hospital/Clinic/Other health care facility

Country Of Registered Address

Netherlands