A Phase 3 interventional study of MVA-BN standard regimen and MVA-BN half-dose regimen in Mpox (Monkeypox), Vaccination and Immunogenicity, sponsored by Jean-Pierre Van geertruyden. Active, not recruiting at 1 site in Democratic Republic of the Congo. Open to participants aged 4 Months to 24 Months, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-04-29.
Sponsored by Jean-Pierre Van geertruyden · Phase 3, Interventional, and Prevention
This Phase 3 double-blinded, randomized study aims to evaluate the safety and immunogenicity of the two-dose MVA-BN mpox vaccine regimen, administered subcutaneously, in infants and children aged 4 to 24 months in the Democratic Republic of the Congo (DRC), a population at high risk of mpox infection and complications. The study will compare the safety and immunogenicity of a full-dose regimen versus a half-dose regimen in this population. A hierarchical testing strategy will be applied as follows: first, non-inferiority of the full-dose regimen in infants/children (4-24 months old) will be evaluated against the full-dose regimen in adults from the POX-MVA-045 study. If non-inferiority is demonstrated, the immunogenicity of the half dose in infants/children (4-24 months old) will subsequently be tested for non-inferiority vs the full dose in adult. The trial will be conducted in Boende, Tshuapa Province, DRC.
The trial plans to enroll 344 male and female infants/children, who will be randomized to receive two doses of the MVA-BN vaccine administered 28 days apart. Participants in Child Group 1 (N=172) will receive the standard vaccine dose (0.5 mL), while those in Child Group 2 (N=172) will receive half the standard dose (0.25 mL), with both groups following the same dosing schedule.
This study builds on positive safety and immunogenicity data from prior trials that support the use of the standard dose regimen in younger children. However, considering the developmental differences in the immune systems of infants and young children/adolescents, it aims to evaluate whether a half-dose regimen can provide similar immunogenicity while potentially reducing reactogenicity. The findings will offer valuable insights into the optimal dosing strategy for this age group, balancing safety and immunogenicity to inform future vaccination recommendations.
This Phase 3 double-blinded, randomised study aims to evaluate the safety and immunogenicity of the MVA-BN mpox vaccine regimen, administered subcutaneously, in infants and children aged 4 to 24 months in the Democratic Republic of the Congo (DRC), a population at high risk of mpox infection. The study will compare the safety and immunogenicity of a full-dose regimen versus a half-dose regimen. A hierarchical testing strategy will be applied as follows: first, non-inferiority of the full-dose regimen in infants/children (4-24 months old) will be evaluated against the full-dose regimen in adults from the POX-MVA-045 study. If non-inferiority is demonstrated, the immunogenicity of the half dose in infants/children (4-24 months old) will subsequently be tested for non-inferiority vs the full dose in adult.
The study will be conducted at the General Reference Hospital of Boende, Tshuapa Province, DRC.
The trial plans to enroll 344 male and female infants/children, who will be randomized to receive two doses of the MVA-BN vaccine administered 28 days apart. Participants in Child Group 1 (N=172) will receive the standard dose of the MVA-BN vaccine (1x10⁸ TCID50 Inf.U./0.5mL), while those in Child Group 2 (N=172) will receive half the standard dose (0.5x10⁸ TCID50 Inf.U./0.5mL). Participants randomized to receive the full dose will receive 0.5 mL of the MVA-BN vaccine, while participants randomized to receive the half dose will receive 0.25 mL of the MVA-BN vaccine.
During the screening visit, parents or legal guardians of the infant/child will provide informed consent and must pass a test of understanding (TOU) to confirm eligibility, with up to three attempts permitted. Demographics, medical history, and vaccination history will be recorded. A basic physical examination will be performed to assess general appearance, key organ systems, growth measurements (weight, length, and head circumference), neurological reflexes, and behavior. Vital signs (heart rate, respiratory rate, temperature, and blood pressure) will also be measured, and an HIV test will be performed.
Randomization will occur after eligibility is confirmed. Participants will be assigned to one of two groups through a double-blind randomization design. A block randomization method will ensure balanced allocation between the two groups, with randomization lists securely provided to unblinded personnel responsible for vaccine preparation. Blinding procedures will ensure that neither parents/legal guardians nor reactogenicity investigators know the group assignments.
Whenever possible, the first vaccine dose (Day 0) will be administered on the same day as the screening visit. However, vaccination may be postponed if the child has a fever or acute infection.
On Day 0, participants will undergo a physical examination, and their vital signs and vaccination/medication history will be assessed. A malaria test will be performed. Blood samples will be collected for baseline immunogenicity testing, including neutralizing antibodies, total binding antibodies, and IgG-binding antibodies.
Participants will then receive their first vaccine dose, administered subcutaneously (standard or half dose, based on randomization). Parents/legal guardians will be provided with a participant journal to document solicited AEs (e.g., pain, swelling, redness at the injection site, fever, irritability) and unsolicited AEs.
On day seven (Day 7), the Parents/legal guardians will be asked to return with the participant journal to report the data on (un)solicited AEs collected during the week after the first dose. Ongoing AEs will continue to be followed until resolution.
On Day 28, participants will undergo a physical examination, and their vital signs, vaccination history, and medication history will be reviewed, and malaria test will be performed. Parents/legal guardians will be asked about unsolicited AEs since the first vaccination. If no concerns are identified, participants will receive the second vaccine dose, and a new participant journal will be provided to document any AEs.
On Day 35, the Parents/legal guardians will be asked to return with the participant journal to report the data on (un)solicited AEs collected during the week after the second dose. Ongoing AEs will continue to be followed until resolution.
On Day 42, Participants will have a physical examination, including assessments of growth, developmental milestones, and general health. Blood samples will be collected to assess neutralising antibodies and total binding antibodies.
Day 56 any unsolicited AEs occurring between Day 35 and Day 56 will be followed up via telephone call or home visit.
On Day 208 (6 months after the second dose), Participants will return for a follow-up assessments, including a physical examination and evaluations of growth and developmental milestones. Vaccination and medication history will also be reviewed. Blood samples will be collected to assess long-term immune responses, including neutralizing antibodies and (total) binding antibodies.
On Day 395 (one year after the second dose), the final follow-up visit will focus on a comprehensive physical examination of the infant/child. Blood samples will be collected to assess long-term immune responses, including neutralizing antibodies and (total) binding antibodies.
72 studies on the registry are indexed under Mpox, Monkeypox; 30 are open to participants now.
This study's enrollment of 344 is above the median of 305 across 36 interventional studies indexed under Mpox, Monkeypox.
Browse Mpox, Monkeypox studies →Jean-Pierre Van geertruyden is the lead sponsor of 4 studies on the registry; 1 is open to participants now.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
The participant's parent or legal guardian must pass (≥9/10) the TOU after being advised of the risks and benefits of the trial in a language understood by the parent/guardian and before performing any trial-specific procedures.
- Note: If the participant's parent or guardian fails the TOU test on the first attempt, he/she must be retrained on the purpose of the study and must take the test again (2 repeats are allowed). If the participant's parent/guardian fails on the third attempt, the screening or consenting procedures should not continue.
The participant must be generally healthy in the investigator's clinical judgment and on the basis of vital signs assessed at day 1 screening with no severe (chronic) conditions (as far as medically known) that might interfere with vaccine assessment.
- Note: -positive subjects can be enrolled as long as their general condition is good, i.e., they are on antiretroviral treatment or have no signs or symptoms of , diagnosed on the basis of physical examination, medical history, and the investigator's clinical judgment.
The participant's parent(s) or guardian(s) must be willing to provide verifiable identification and have means to be contacted (phone number or address).
Exclusion Criteria:
Acute or chronic medical condition that, in the opinion of the investigator, would render the trial procedures unsafe or would interfere with the evaluation of responses, including but not limited to neurologic, cardiovascular, respiratory, hepatic, hematologic, rheumatologic, endocrine, gastrointestinal, renal, autoimmune, or conditions.
- Note: Participants with minor acute illnesses such as mild diarrhoea or mild upper respiratory tract infection or temperature ≥38.0ºC at screening will be excluded from enrolment at that time but may be rescheduled for re-screening later if feasible.
Presence of significant medical conditions or findings at screening or vital signs for which, in the opinion of the gynaecologist, participation would not be in the best interest of the participant (e.g., compromise the safety or well-being) or that could prevent, limit, or confound the protocol-specified assessments.
Chronic administration (defined as more than 14 days) of systemic high dose immune-suppressant drugs (2 mg/kg/day or more of prednisolone or its equivalent or 20 mg/day or more for children who weigh more than 10 kg) from 6 months prior to first trial vaccination to trial conclusion.
- Note: Participants receiving antiretroviral (ARV) medication for the management of infection are eligible for inclusion, provided they meet inclusion criterion 5.
Received an investigational or nonregistered drug or vaccine or used an invasive investigational or nonregistered medical device within 30 days prior to vaccination or current or planned participation in another clinical study during the study.
- Note: Participation in an observational clinical study is allowed.
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Male or Female infants/children aged 4-24 months will be administered each vaccine of the MVA-BN standard or half-dose regimen (depending on the randomisation group) by SC administration into the anterolateral thigh. For children closer to 24 months old, the deltoid of the upper arm can also be used (preferably the nondominant arm, if already known).
Biological: MVA-BN standard regimen
Male of female infants/children aged 4-24 months will be administered each vaccine of the MVA-BN standard or half-dose regimen (depending on the randomisation group) by SC administration into the anterolateral thigh. For children closer to 24 months old, the deltoid of the upper arm can also be used (preferably the nondominant arm, if already known).
Biological: MVA-BN half-dose regimen
Historical data from healthy adults aged 18 to 50 years old, and children aged 2 to \<12 years old from the POX-MVA-045 study (NCT06549530), will be used for safety and immunogenicity comparisons. These participants will be vaccinated in the deltoid of the upper arm.
Biological: MVA-BN standard regimen
The MVA-BN vaccine, with the active ingredient: Modified Vaccinia Ankara-Bavarian Nordic, will be administered as a standard two-dose regimen at 1x10\^8 TCID50 Inf.U./0.5 mL. The doses will be given 28 days apart (±3 days) via subcutaneous injection into the deltoid muscle, preferably in the non-dominant arm.
The MVA-BN vaccine, with the active ingredient: Modified Vaccinia Ankara-Bavarian Nordic, will be administered as two half doses of the standard regimen; meaning infants/children allocated to Child Group 2 will receive 0.25 mL of the 0.5 mL. 1x10\^8 TCID50 Inf.U./0.5 mL standard regimen. The doses will be given 28 days apart (±3 days) via subcutaneous injection into the deltoid muscle, preferably in the non-dominant arm. Only one vial will be used per infant/child.
Immunogenicity of Full-Dose vs. Half-Dose MVA-BN Vaccine in Infants/Children.
Compare the immunogenicity of full-dose and half-dose MVA-BN vaccine regimens in infants/children (4-24 months), with neutralising antibody responses measured by PRNT assays 14 days post-second dose, against the full-dose regimen in adults from the POX-MVA-045 study. A hierarchical testing strategy will be applied as follows: first, non-inferiority of the full-dose regimen in infants/children (4-24 months old) will be evaluated against the full-dose regimen in adults from the POX-MVA-045 study. If non-inferiority is demonstrated, the immunogenicity of the half dose in infants/children (4-24 months old) will subsequently be tested for non-inferiority vs the full dose in adult.
Time frame: 14 days after the second dose
Safety and Reactogenicity of the MVA-BN Vaccine in Infants/Children Compared to Adults from the POX-MVA-045 Study
Evaluate the safety and reactogenicity of the standard MVA-BN regimen administered subcutaneously to infants/children (4-24 months), compared to the standard regimen in adults from the POX-MVA-045 study. Safety endpoints include SAE, AESI, MAAE, and AE occurrences; reactogenicity endpoints include solicited local and systemic events.
Time frame: Throughout the trial period; from the first dose to one year after the second dose
Immunogenicity of Standard and Half-Dose Regimens in Infants/Children vs. Adults and Older Children.
To assess the immunogenicity of the MVA-BN standard and half dose regimen administered subcutaneously (SC) in eliciting neutralising antibodies in infants/children (4-24 months old) compared to adults and children (2-\<12 years old) of the POX-MVA-045 study receiving the standard MVA-BN regimen at baseline and all collected timepoints after the second dose.
Time frame: From baseline to one year after the second dose
Total Binding Antibody Response in Infants/Children vaccinated with MVA-BN Vaccine standard regimen and adults and children of the POX-MVA-045 study
To assess the immunogenicity of the MVA-BN standard and half dose regimen administered subcutaneously (SC) in eliciting total binding antibodies in infants/children (4-24 months old) compared to adults and children (2-\<12 years old) of the POX-MVA-045 study at baseline and all collected timepoints after the second dose.
Time frame: From baseline to one year after the second dose
Immunogenicity of Standard vs. Half-Dose Regimens in Infants/Children.
To assess the immunogenicity of the MVA-BN standard versus half dose regimen administered subcutaneously (SC) in eliciting neutralising antibodies in infants/children (4-24 months old) at baseline and all collected timepoints after the second dose.
Time frame: From baseline to one year after the second dose
Total Binding Antibody Response with Standard vs. Half-Dose Regimens in Infants/Children.
To assess the immunogenicity of the MVA-BN standard versus half dose regimen administered subcutaneously (SC) in eliciting total binding antibodies in infants/children (4-24 months old) at baseline and all collected timepoints after the second dose.
Time frame: From baseline to one year after the second dose
Safety and Reactogenicity of Standard vs. Half-Dose MVA-BN Vaccine in Infants/Children.
To evaluate the reactogenicity and safety of the MVA-BN standard regimen administered SC to infants/children (4-24 months old) compared to infants/children (4-24 months old) receiving the half dose regimen.
Time frame: Throughout the trial period; from the first dose to one year after second dose
Safety and Reactogenicity of Standard MVA-BN Vaccine in Infants/Children Compared to Older Children.
To evaluate the reactogenicity and safety of the MVA-BN standard regimen administered SC to infants/children (4-24 months old) compared to children 2 to \<12 years-old receiving the standard regimen (POX-MVA-045).
Time frame: Throughout the trial period; from first dose to one year after second dose
Impact of Demographic Variables on Neutralising Antibody Responses in Infants/ Children Vaccinated with Half-Dose Regimen
To explore demographic variables (e.g. age, sex, malaria exposure, malnutrition, etc.) that impact the neutralising and total binding antibody response in the serum of infants/children (4-24 months old) vaccinated with the half-dose MVA-BN regimen.
Time frame: From enrolment to one year after the second dose
Impact of Demographic Variables on Total Binding Antibody Responses with Standard Regimen
To explore demographic variables (e.g. age, sex, malaria exposure, malnutrition, etc.) that impact of neutralising and total binding antibody response against vaccinia in the serum of infants/children (4-24 months old) vaccinated with the standard MVA-BN regimen.
Time frame: From enrolment to one year after the second dose
Neutralising Antibody Response in Standard and Half-Dose Regimens in a Subset of Infants/Children.
To assess the immunogenicity of the MVA-BN standard regimen, administered SC, in eliciting neutralising antibodies against the monkeypox and vaccinia virus in a subset (10%) of 4 to 24-month-old infants/children compared to a subset (10%) of infants/children receiving a half-dose regimen (0.5 x108 TCID50 Inf.U./0.5mL) at baseline, 2 weeks, 6 months and 12 months after the second dose.
Time frame: From baseline to one year after the second dose
Total IgG Response Against Multiple MPXV Antigens with Standard and Half-Dose Regimens.
To assess the immunogenicity of the MVA-BN standard regimen, administered SC, in eliciting Total IgG in serum with multiple MPXV specific antigens (B6R, B2R, E8L, M1R, A35, H3L) in a subset (10%) of 4 to 24-month-old infants/children compared to a subset (10%) of infants/children receiving a half-dose regimen (0.5 x108 TCID50 Inf.U./0.5mL) at baseline, 2 weeks, 6 months and 12 months after the second dose.
Time frame: From enrolment to 1 year after the second dose
Plan to share: No
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Jean-Pierre Van geertruyden