A Phase 3 interventional study of LC16m8 in Monkeypox, sponsored by Universidad Nacional de Colombia. Active, not recruiting at 3 sites in Colombia. Open to participants aged 18 Years to 50 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2025-09-04.
Sponsored by Universidad Nacional de Colombia · Phase 3, Interventional, and Prevention
Background: Mpox is a zoonotic disease caused by the mpox virus (MPXV). It has been endemic in West and Central African countries. However, the soaring number of those has been reported in non-endemic countries since May 2022, making World Health Organization (WHO) declare a global mpox Public Health Emergency of International Concern in July 2022. Those with mpox are primarily young men (96%, and median age of 34 [interquartile range (IQR):29-41 years]), and 84% are self-identified homosexual, bisexual, and men who have sex with men (MSM) . Furthermore, about half of these mpox cases with known human immunodeficiency virus 1(HIV-1, hereafter shown as HIV). WHO recommended prioritizing vaccinating those populations as high-risk populations, including those with HIV, since they will be severely ill if infected mpox virus (MPXV). The smallpox vaccine is expected to offer cross-immunity against MPXV. Under these circumstances, WHO included LC16m8 in the recommended vaccine lists for mpox as the product is expected to have cross-efficacy and immunogenicity against MPXV. Additionally, the safety profile was demonstrated in both adults and children, including infants who have low immuno-functions. Given that Colombia has the fifth highest mpox prevalence worldwide, WHO encouraged the authorities to implement vaccine programs while evaluating the safety and efficacy of LC16m8 as collaborative research. Following WHO initiative, this study is being conducted with the collaboration of various experts from Colombia and Japan on a large scale, with vaccine contributions and funding from Japan and Colombia However, the current infection situation differs from six months ago, and there have been few recent cases of MPXV infection in the country.
Primary objective: To determine the efficacy of the replicating attenuated live vaccinia virus vaccine LC16m8 against laboratory-confirmed mpox and safety in a Colombian population with a high risk of being infected with MPXV(See the Inclusion Criteria), by comparing the immediate vaccination group and the delayed vaccination groups to assess safety and tolerability until 180 days after vaccination. Study design: An open randomized deployment study (1:1 Immediate and Delayed vaccination group).
Study population: People at high risk of serious illness if infected with MPXV and those who engage in risk behaviors for acquiring MPXV infection.
Hypothesis: LC16m8 is a safe and effective vaccine for high-risk immunocompromised populations, including those living with HIV.
Intervention evaluation plan: Vaccinate with LC16m8 those people randomly assigned to two groups: immediate and deferred vaccination 1:1 with a follow-up period of 180 days to evaluate new cases infected by MPXV.
General design: This research is being carried out within the framework of the mpox vaccination implementation program in Colombia. It comprises the following three complementary components:
STUDY SECTION 1: Participants will receive LC16m8 vaccine within 6 weeks (immediate vaccination) or 6 weeks later (delayed vaccination) after randomization. Both groups will be followed up at 14, 30 and 180 days after vaccination, mainly through phone calls.
The study will compare the incidence of new MPXV infections in the early vaccination group from day 14 to day 42 after vaccination with the incidence of rate at which new MPXV infections occur in the delayed vaccination group from 42 days before to 14 days after vaccination; this comparison will be made from the hazard ratio or proportional hazard model.
Additionally, the immune response, including neutralizing antibody titers, will be evaluated from the day of vaccination (Day 1) to 180 days post-vaccination in 60 participants, who will be selected from a single research center and only belonging to the immediate vaccination group. Two 5 mL blood samples (converted to serum) will be collected from the participants for immunogenicity assessments at the following time points: Days 0, 14 (+/-2), 30 (+/-2), and 180 (+/-7) post-vaccination. Another blood sample for immunogenicity assessment will be collected before the vaccine is administered on Day 0.
Safety events will be intensively sought, especially in the first 14 days after vaccine administration and all those arising within 180 days post-vaccination. Participants will also self-report symptoms through a mobile application designed for this purpose.
STUDY SECTION 2 AND 3 (NESTED STUDIES)
- Study of cohorts supported on the same population base: A total of 1,000 vaccinated individuals, including participants in section 1 of the study, will make up the exposed group. The unexposed group will consist of 4,000 unvaccinated individuals from the same population base (a list of HIV patients with a CD4 count greater than 200 cells/ml and PrEP users). who are patients with HIV and CD4 greater than 200 cells/mm3, and PrEP users. The group of unvaccinated individuals are people who meet the study's criteria but did not agree to be vaccinated or withdrew their consent. We will compare the cumulative incidence of these two groups over a 180-day period. We will obtain information about non-participants and withdrawals from the records at the INS and local health entities. We will use the hazard ratio (HR) to compare these groups, and we will also conduct a propensity score analysis.The objective is to demonstrate the effectiveness and safety of the LC16m8 replicating vaccine against laboratory-confirmed MPXV in a Colombian population at high risk of MPXV infection (see inclusion criteria).
Assumptions:
Ratio of vaccinated:unvaccinated: 1:4
The incidence of the event (Mpox case) is considered to be 0.4% per period in the exposed group (I Exp (+)) and 1.6% per period in the unexposed group (I exp (-)), in accordance with the current situation of Mpox infection in Colombia.
Incidence in vaccinated 4/1000 = 0.004 Incidence in unvaccinated 64/4000 = 0.016 RR** = 0.2756 (95% CI: 0.1057 ; 0.7185) **Relative risk (RR): Risk (Rx) in unvaccinated/Rx in vaccinated RAR***: -1.2888 (95% CI: -2.247; - 0.3306) RRR= 0.7244 (95% CI: 0.2815; 0.8943) Power: 0.92 where RR is relative risk, RAR is absolute risk reduction and RRR is relative risk reduction.
The Ho could be rejected.
- Cohort study compared to the real-world cohort: There will be no sample size because all the information from the databases will be used in the cohort, so a sample is not necessary since we will take all the subjects in HIV and PrEP programs.
72 studies on the registry are indexed under Mpox, Monkeypox; 30 are open to participants now.
This study's planned enrollment of 8,686 is above the median of 305 across 36 interventional studies indexed under Mpox, Monkeypox.
Browse Mpox, Monkeypox studies →Universidad Nacional de Colombia is the lead sponsor of 39 studies on the registry; 6 are open to participants now.
Counted across the registry records on this site, refreshed daily.
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.
Sex: Males and females
Any of the following conditions including clinical conditions /manifestation:
A female participant is eligible to participate if the participant meets one of the inclusion criteria numbered -1, -2 or -3 above. The participant cannot be pregnant or lactating. Additionally, the female participant must meet one of the following conditions:
Subjects with an unstable medical condition as determined by their initial medical history, physical examination, or laboratory results
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.
The number of CD4 cells, a type of white blood cell, in a given amount of blood. It is used to follow how well the immune system is doing in HIV.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
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.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
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.
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.
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
Vaccines made with a weakened form of the germ, such as measles–mumps–rubella (MMR), chickenpox and yellow fever. They can be risky when the immune system is weakened. Flu injections are not live; the nasal flu spray is.
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.
CD4 count
The number of CD4 cells, a type of white blood cell, in a given amount of blood. It is used to follow how well the immune system is doing in HIV.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Postmenopausal
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Excipients
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
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.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
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.
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.
LVEF (left ventricular ejection fraction)
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Live vaccines
Vaccines made with a weakened form of the germ, such as measles–mumps–rubella (MMR), chickenpox and yellow fever. They can be risky when the immune system is weakened. Flu injections are not live; the nasal flu spray is.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
This vaccin is a yellowish-yellow dry preparation containing live vaccinia virus (strain LC16m8). When the accompanying solvent is added, it dissolves rapidly to form a clear or slightly cloudy yellowish-red or reddish liquid. The ingredients of this vaccin are contained in 0.5 mL of a solution of this product dissolved in 0.5 mL of the accompanying solvent (20 vol% glycerin-added water for injection). Just one dose of vaccine will be administered according to standardized operating procedure (SOP). Briefly, the vaccine is dissolved with 0.5 mL of a diluent provided. The reconstituted vaccine is usually administered percutaneously at a dose of approximately 0.025 mL by the multiple puncture technique using a bifurcated needle. The number of punctures will be 15 times. Procedures for vaccine administration are described in detail in the SOP. The participant must be observed at the vaccination site for 30 minutes after vaccine administration to observe possible immediate reactions.
Biological: LC16m8
The use of placebo as a control group is essential to scientifically assess the efficacy of vaccines in clinical trials and to obtain reliable evidence in preventing the onset of disease. However, the use of a placebo is unethical. Subjects are at high risk of mpox and must not be given a placebo. Therefore, a design was applied in which the immediate treatment group was evaluated with the delayed group as a control group. A period of six weeks was set aside between the immediate and delayed treatment groups to be used for logistics, such as preparations and delivery of the vaccine in the delayed treatment group. It is ethical, for the same reason, because it prevents inequities based on the abovementioned reasons.
Biological: LC16m8
LC16m8 should be stored at temperatures between -35°C and -20°C. The product should not be stored at temperatures below -35°C, because deterioration or damage of the rubber stopper could occur. The virus in this product is sensitive to sunlight and is quickly inactivated, so care should be taken to avoid exposure to light, both before or after reconstitution. Carefully examine the content at the time of reconstitution. Do not use if precipitation, contamination of foreign substances, or other abnormalities are observed. This product should be dissolving the drug immediately before inoculation. Once dissolved, it should be used immediately. Since this product does not contain thimerosal, once the stopper is removed, any solution remained in the vial must be disposed of. Do not restore or reuse the remaining solution. Shelf Life: 10 years from the date of passing the national test for lot-release Bottle containing about 250 doses
Incidence rate of mpox infection between the immediate versus delayed vaccination groups from day 15 to day 56 post-vaccination of the immediate group.
The incidence rate of new cases of mpox (laboratory-confirmed) will be calculated with a 95% confidence interval (CI) based on the Poisson distribution for each vaccination group. The time to the onset of the first occurrence of a confirmed mpox case in the subject will be summarized graphically using the Kaplan-Meier method.
Time frame: For immediate vaccination group: from days 15th to 56th post vaccination. For delayed vaccination group: from enrollment to the day of vaccination (42 days later)
Incidence of adverse events between the vaccination groups
Proportion of adverse events (serious and non-serious) presented in participants included in the two vaccination groups (immediate and delayed)
Time frame: up to 6 months post vaccination
Incidence rate of mpox infection between the vaccinated cohort versus the unvaccinated cohort
The incidence rate of new cases of mpox (laboratory-confirmed) will be calculated with a 95% confidence interval (CI) based on the Poisson distribution for each cohort. The time to the onset of the first occurrence of a confirmed mpox case in the subject will be summarized graphically using the Kaplan-Meier method.
Time frame: 6 months post vaccination
Frequency of laboratory-confirmed severe cases of MPOX in the immediate and delayed vaccination groups.
Proportion of participants with confirmed MPOX that presented severe symptoms requiring hospitalization, emergency department care, or death associated with MPOX.
Time frame: 6 months post-vaccination
Incidence rate of mpox suspected cases without laboratory confirmation between the immediate versus delayed vaccination groups from day 15 to day 56 post-vaccination of the immediate group.
Mpox suspected cases correspond to participants that present with skin lesions to the emergency room or treating patient.
Time frame: - For immediate vaccination group: from days 15th to 56th post vaccination. For delayed vaccination group: from enrollment to the day of vaccination (42 days later
Proportion of patients with seroconversion of geometric mean neutralizing titer (GMT) of LC16m8.
Seroconversion is considered in cases where the titer on day 30 is 4 times higher than on day 0.
Time frame: up to 6 months post vaccination
Geometric mean of LC16m8 neutralizing titer by vaccination group.
overall geometric mean of each group (immediate and delayed vaccination)
Time frame: up to 6 months post vaccination
Geometric mean of LC16m8 neutralizing titer by helper T lymphocytes (CD4) count in each vaccination group
Subgroups of patients with a CD4 count of 350 or less and those with a CD4 count greater than 350 will be compared for each vaccination group.
Time frame: up to 6 months post vaccination
Maximum lesion area (MLA) in mm² after scarification with vaccination LC16m8
take area measured 14 days post vaccination
Time frame: up to 6 months post vaccination
Plan to share: No
Ran from Dec 2023 to primary completion in Aug 2024, 8 months.
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Universidad Nacional de Colombia