Lassa FeverPhase 1FIRST-IN-MOPNCT07833436
A Trial to Evaluate the Safety, Immunogenicity and the Optimal Dose of MOPEVAC-Las Vaccine Candidate Against Lassa Fever
A Phase 1 study testing Low dose MOPEVAC-Las vaccine, Intermediate dose MOPEVAC-Las vaccine and High dose MOPEVAC-Las vaccine in people with Lassa Fever, run by Institut Pasteur at 1 site in France.
Trial summary
Lassa fever is an acute viral disease belonging to the category of viral hemorrhagic fevers. It is endemic in West Africa. Outbreaks occur every year, and it is estimated that between 100 000 and 300 000 individuals are infected each year, with a fatality rate for symptomatic cases that ranges between 15 and 30%. Read more about this study
- Who is it for?
- Ages 18 to 55 yearsHealthy volunteers can take part
- Conditions the study is for
- Lassa Fever
- What is being tested?
- Low dose MOPEVAC-Las vaccine, Intermediate dose MOPEVAC-Las vaccine and High dose MOPEVAC-Las vaccine
- Type of treatment
- Vaccines, Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 72 participants
- Where
- 1 siteFrance
- Study dates
- 28 Sep 2026to Dec 2028
- Phase
- Phase 1
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 55 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Males and females between the ages of 18 and 55 years (at the time of consent).
- Healthy participant, according to the investigator's clinical judgment, as established by medical history, vital signs, physical examination, and laboratory assessments.
- Participant with a body mass index (BMI) between 18,5 kg/m2 and 30.0 kg/m2.
- Provide written informed consent before initiation of any study procedures.
- A female participant is eligible for this study if she is not pregnant, given by a negative serum pregnancy test at screening and a negative urine pregnancy test at V1 (first injection), nor breastfeeding and if she meets any of the following criteria:
- Of non-childbearing potential (i.e., women who have had a hysterectomy or surgical tubal ligation or are postmenopausal, as defined by no menses in greater than or equal to 1 year).
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- Of childbearing potential but having sexual relations exclusively with female partners.
- Of childbearing potential but has been and agrees to continue practicing highly effective contraception or abstinence (if this is the preferred and usual lifestyle of the participant) from 30 days prior to vaccination up to 6 months after the last injection (D242).
- Highly effective methods of contraception include 1 or more of the following:
- Male partner who is sterile prior to the female participants entry into the study and is the sole sexual partner for the female participant
- Compliant hormonal therapy (oral, intravaginal, transdermal, implantable or injectable)
- An intrauterine hormone-releasing system (IUS)
- An intrauterine device (IUD) with a documented failure rate of < 1%
- A female participant is eligible if she agrees to abstain from donating oocyte from the screening visit up to 6 months after the last injection (D242)
- A male participant is eligible if he agrees to:
- Use a condom (with/without spermicidal product) from the screening visit up to 6 months after the last injection (D242) except if the male participant is sterile; the unique female sexual partner is postmenopausal (defined as no menses for 12 months without an alternative medical cause), is permanently sterilized (e.g. hysterectomy or tubal ligation), or use a highly effective method of contraception; or if he has sexual relations exclusively with male partners
- Not donate sperm from the screening visit up to 6 months after the last injection (D242)
- Not plan to father a child from the screening visit up to 6 months after the last injection (D242)
- Negative HIV 1/2 antibody/antigen test, Hepatitis B surface antigen (HBsAg), and Hepatitis C virus (HCV) antibody.
- Able to understand and comply with planned study procedures and willing to be available for all study-required procedures, visits and calls for the duration of the study.
- Willing to abstain from donating whole blood or blood derivatives, tissue or organ all along the study.
- Affiliated to a social security system (except state medical aid).
Who cannot join
- Subjects previously infected by Lassa Virus.
- Previous vaccination with an investigational Lassa fever vaccine.
- Subjects who travelled in the past 12 months prior the first injection or plan to travel during the study in a Lassa-endemic country .
- Subjects who used to live in a Lassa-endemic country, or who are regularly traveling to a Lassa-endemic country.
- History of presence of pulmonary disorders (e.g. COPD, etc.) or asthma in adulthood.
- History of or present thrombocytopenia and/or bleeding disorders.
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- History of or present hearing deficiency or tympanic vulnerability (e.g. manifested by recurrent ear infections).
- A positive serum pregnancy test at screening or urine pregnancy test prior to study injection, women who are planning to become pregnant during the study, or women who are breastfeeding.
- Clinically relevant history of or current renal, hepatic, gastrointestinal, cardiovascular, respiratory, skin, hematological, endocrine, inflammatory, autoimmune, central nervous system or neurological diseases or clinically relevant abnormal laboratory values.
- Use of immunosuppressive drugs like corticosteroids (excluding topical preparations and inhalers) within 3 months prior to the first vaccination or 6 months for chemotherapies and all along the study.
- A diagnosis of schizophrenia, bipolar disease, or history of hospitalization for a psychiatric condition or previous suicide attempt.
- A history of treatment for any other psychiatric disorder in the past 3 years that increases the risk to the subject in the opinion of the investigator.
- Received immunoglobulin or other blood product within 3 months prior to enrollment or planned receipt of immunoglobulin or a blood product through study completion.
- Vaccination within 3 weeks prior to first injection or planning to receive any licensed vaccine before D88 (e.g. COVID-19 vaccine, Inactivated influenza vaccine).
- History of severe adverse reactions to vaccine administration, including anaphylaxis and related symptoms, such as urticaria, respiratory difficulty, angioedema and abdominal pain to vaccines, or history of known or suspected allergic reaction likely to be exacerbated by any component of the MOPEVAC-Las vaccine.
- Participation in another investigational clinical study within four weeks before the screening visit or planned before the study completion.
- Individuals who are living and/or working with severely immunocompromised people, pregnant women, lactating women, children under 12 months old, or any other individual that, in the judgment of the investigator, might be at increased risk.
- Individual in a direct relationship with an investigator/study team or with the sponsor. Direct dependent relationships include close relatives (e.g. children, parents, partner, siblings, etc.) as well as employees of the clinical study site or the sponsor.
- Any condition that, in the opinion of the investigator, may interfere with the aim of the study or the safety or wellbeing of the subject.
- Subjects with confirmed or suspected immunodeficiency.
- Exposure to an individual with confirmed Lassa virus within the past 3 weeks prior to enrollment.
- Subject with an acute disease and/or fever (body temperature ≥ 38°C) at the time of the 1st vaccination visit.
- Current heavy smoker defined as smoking at least 20 cigarettes (1 pack, or equivalent) per day or former heavy smoker who was an active heavy smoker within the last year prior to the screening visit or has a total smoking history of ≥ 1 pack per day for 10 years or more; or excessive use of electronic cigarettes according to the investigator's judgment.
- Current or history of alcohol or drug abuse during the previous 3 years.
- Presence of tattoos that, in the opinion of the investigator, would preclude evaluation of the injection site.
- Volunteer registered in the French Health Ministry computerized file and not authorized to participate in a clinical trial.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
France1 site, 1 recruiting
- Recruiting
Centre d'Investigation Clinique en Vaccinologie Cochin-Pasteur
Paris, 75014
Odile Launay, MD, +33158412858, odile.launay@aphp.fr
Thalia Garcia Tellez, +33158413533, thalia.garciatellez@aphp.fr
About this study
Official title: A Randomized, Placebo-controlled Trial, to Evaluate the Safety, Immunogenicity and the Optimal Dose of MOPEVAC-Las Vaccine Candidate Against Lassa Fever, in Healthy Volunteers Consisting of an Unblinded Dose Escalation and a Blinded Treatment Phase
Lassa fever is an acute viral disease belonging to the category of viral hemorrhagic fevers. It is endemic in West Africa. Outbreaks occur every year, and it is estimated that between 100 000 and 300 000 individuals are infected each year, with a fatality rate for symptomatic cases that ranges between 15 and 30%. There is no efficient treatment against the disease, as ribavirin, the only licensed therapy, is at best poorly efficient.
MOPEVAC-Las is a live-attenuated vaccine candidate targeting Lassa virus.
Read more
The objective of this phase 1 clinical trial is to evaluate the safety of the MOPEVAC-Las vaccine candidate on healthy volunteers. It will also evaluate the immunogenicity and optimal dose of the vaccine candidate.
The main questions it aims to answer are:
- What are the safety and tolerability of the MOPEVAC-Las vaccine candidate following two intramuscular injections in healthy volunteers ?
- Are cell-mediated immunity and humoral immunity induced by the MOPEVAC-Las vaccine ?
- What is the optimal dose of MOPEVAC-Las vaccine regarding safety, tolerability and immunogenicity ?
Researchers will compare the MOPEVAC-Las vaccine candidate to a placebo (a look-alike substance that contains no drug).
Read the detailed description
72 subjects will be enrolled in three treatment groups: treatment group A will receive a "low" dose vaccine, treatment group B an "intermediate" dose vaccine and treatment group C a "high" dose vaccine. In addition, 6 subjects will receive a placebo in each treatment group.
Participants will:
- Receive an two injections of MOPEVAC-Las vaccine candidate or placebo, on days 0 and 60
- Visit the clinical site for 11 visits. Among them, one is the screening visit, two correspond to injection visits and 8 are follow-up visits.
Each subject will participate in the trial for 14 months.
- Conditions
- Lassa Fever
- Being tested
- Low dose MOPEVAC-Las vaccine, Intermediate dose MOPEVAC-Las vaccine, High dose MOPEVAC-Las vaccine, Saline Solution for Injection
- Keywords
- Lassa fever, Phase 1, Vaccine
- Medical subject headings
- Lassa Fever
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Low dose MOPEVAC-Las vaccineBiological
2 intramuscular injections of low dose MOPEVAC-Las vaccine candidate (5 x 10^4 FFU per injection), on days 0 and 60
Intermediate dose MOPEVAC-Las vaccineBiological
2 intramuscular injections of intermediate dose MOPEVAC-Las vaccine candidate (5 x 10^5 FFU per injection), on days 0 and 60
High dose MOPEVAC-Las vaccineBiological
2 intramuscular injections of high dose MOPEVAC-Las vaccine candidate (5 x 10^6 FFU per injection), on days 0 and 60
Saline Solution for InjectionDrug
2 intramuscular injections of placebo on days 0 and 60
| Study group | Role | What they receive |
|---|---|---|
| Low dose | Experimental | Not described Receives: Biological: Low dose MOPEVAC-Las vaccine; Drug: Saline Solution for Injection |
| Intermediate dose | Experimental | Not described Receives: Biological: Intermediate dose MOPEVAC-Las vaccine; Drug: Saline Solution for Injection |
| High dose | Experimental | Not described Receives: Biological: High dose MOPEVAC-Las vaccine; Drug: Saline Solution for Injection |
What is being measured
The primary outcome is the main question the study is designed to answer.
Rate of solicited and unsolicited Adverse Events (AEs) during the treatment period up to 28 days after each injection.
Measured: From each injection to 28 days later
Secondary outcomes (4)
Measurement of functional CD4+ and CD8+ T- cells to assess cell-mediated immunity specific for MOPEVAC-Las
Measured: On days 14 and 28 after each injection, and 6 months and 1 year after the second injection (i.e. day 242 and 425)
Measurement of anti-LASV antibodies determined by ELISA assay
Measured: The day of each injection and 7, 14 and 28 days after each injection
Quantification of functional, neutralizing antibodies via Virus Neutralization Test (VNT)
Measured: On days 0, 14, 28, 60, 74, 88, 242 and 425
Rate of serious adverse events (SAEs), serious adverse reactions (SARs), suspected unexpected serious adverse reactions (SUSARs) and adverse events of special interest (AESI)
Measured: From the first injection until 1 year after the second injection
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted22 Sep 2026
- Study start28 Sep 2026
- Primary completionApr 2028 (estimated)
- Study completionDec 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Lassa FeverStudies of the same condition, open and under way.
- More trials run by Institut PasteurThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 1
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Sequential
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 72 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Institut Pasteur
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Sylvain Baize, Study director, Institut Pasteur
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07833436
- Sponsor's protocol ID
- 2021-063
- Acronym
- FIRST-IN-MOP
- Status last verified
- Sep 2026
- First submitted
- 16 Sep 2026
- Last updated
- 13 Oct 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Study at a glance
From the registry record, last updated by the sponsor on 13 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Randomized, Placebo-controlled Trial, to Evaluate the Safety, Immunogenicity and the Optimal Dose of MOPEVAC-Las Vaccine Candidate Against Lassa Fever, in Healthy Volunteers Consisting of an Unblinded Dose Escalation and a Blinded Treatment Phase
- ClinicalTrials.gov ID
- NCT07833436
- Acronym / sponsor ID
- FIRST-IN-MOP / 2021-063
- Conditions
- Lassa Fever
- Keywords
- Lassa fever, Phase 1, Vaccine
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 72 participants (estimated)
- Lead sponsor
- Institut PasteurIndustry (pharma, biotech, devices)
- Study start
- 28 Sep 2026 (actual)
- Primary completion
- Apr 2028 (estimated)
- Study completion
- Dec 2028 (estimated)
- First posted
- 22 Sep 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Lassa fever is an acute viral disease belonging to the category of viral hemorrhagic fevers. It is endemic in West Africa. Outbreaks occur every year, and it is estimated that between 100 000 and 300 000 individuals are infected each year, with a fatality rate for symptomatic cases that ranges between 15 and 30%. There is no efficient treatment against the disease, as ribavirin, the only licensed therapy, is at best poorly efficient.
MOPEVAC-Las is a live-attenuated vaccine candidate targeting Lassa virus.
The objective of this phase 1 clinical trial is to evaluate the safety of the MOPEVAC-Las vaccine candidate on healthy volunteers. It will also evaluate the immunogenicity and optimal dose of the vaccine candidate.
The main questions it aims to answer are:
- What are the safety and tolerability of the MOPEVAC-Las vaccine candidate following two intramuscular injections in healthy volunteers ?
- Are cell-mediated immunity and humoral immunity induced by the MOPEVAC-Las vaccine ?
- What is the optimal dose of MOPEVAC-Las vaccine regarding safety, tolerability and immunogenicity ?
Researchers will compare the MOPEVAC-Las vaccine candidate to a placebo (a look-alike substance that contains no drug).
Detailed description
72 subjects will be enrolled in three treatment groups: treatment group A will receive a "low" dose vaccine, treatment group B an "intermediate" dose vaccine and treatment group C a "high" dose vaccine. In addition, 6 subjects will receive a placebo in each treatment group.
Participants will:
- Receive an two injections of MOPEVAC-Las vaccine candidate or placebo, on days 0 and 60
- Visit the clinical site for 11 visits. Among them, one is the screening visit, two correspond to injection visits and 8 are follow-up visits.
Each subject will participate in the trial for 14 months.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Sequential
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 3
| Arm | Type | Receives |
|---|---|---|
| Low dose | Experimental | Biological: Low dose MOPEVAC-Las vaccine, Drug: Saline Solution for Injection |
| Intermediate dose | Experimental | Biological: Intermediate dose MOPEVAC-Las vaccine, Drug: Saline Solution for Injection |
| High dose | Experimental | Biological: High dose MOPEVAC-Las vaccine, Drug: Saline Solution for Injection |
Who may qualify
- Ages
- 18 to 55 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (22 listed)
- Males and females between the ages of 18 and 55 years (at the time of consent).
- Healthy participant, according to the investigator's clinical judgment, as established by medical history, vital signs, physical examination, and laboratory assessments.
- Participant with a body mass index (BMI) between 18,5 kg/m2 and 30.0 kg/m2.
- Provide written informed consent before initiation of any study procedures.
- A female participant is eligible for this study if she is not pregnant, given by a negative serum pregnancy test at screening and a negative urine pregnancy test at V1 (first injection), nor breastfeeding and if she meets any of the following criteria:
Key exclusion criteria (26 listed)
- Subjects previously infected by Lassa Virus.
- Previous vaccination with an investigational Lassa fever vaccine.
- Subjects who travelled in the past 12 months prior the first injection or plan to travel during the study in a Lassa-endemic country .
- Subjects who used to live in a Lassa-endemic country, or who are regularly traveling to a Lassa-endemic country.
- History of presence of pulmonary disorders (e.g. COPD, etc.) or asthma in adulthood.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Low dose MOPEVAC-Las vaccine2 intramuscular injections of low dose MOPEVAC-Las vaccine candidate (5 x 10^4 FFU per injection), on days 0 and 60 | Biological | Low dose |
| Intermediate dose MOPEVAC-Las vaccine2 intramuscular injections of intermediate dose MOPEVAC-Las vaccine candidate (5 x 10^5 FFU per injection), on days 0 and 60 | Biological | Intermediate dose |
| High dose MOPEVAC-Las vaccine2 intramuscular injections of high dose MOPEVAC-Las vaccine candidate (5 x 10^6 FFU per injection), on days 0 and 60 | Biological | High dose |
| Saline Solution for Injection2 intramuscular injections of placebo on days 0 and 60 | Drug | High dose, Intermediate dose, Low dose |
Primary outcome
Rate of solicited and unsolicited Adverse Events (AEs) during the treatment period up to 28 days after each injection.
Time frame: From each injection to 28 days later
4 secondary outcomes
Measurement of functional CD4+ and CD8+ T- cells to assess cell-mediated immunity specific for MOPEVAC-Las
Time frame: On days 14 and 28 after each injection, and 6 months and 1 year after the second injection (i.e. day 242 and 425)
Measurement of anti-LASV antibodies determined by ELISA assay
Time frame: The day of each injection and 7, 14 and 28 days after each injection
Quantification of functional, neutralizing antibodies via Virus Neutralization Test (VNT)
Time frame: On days 0, 14, 28, 60, 74, 88, 242 and 425
Rate of serious adverse events (SAEs), serious adverse reactions (SARs), suspected unexpected serious adverse reactions (SUSARs) and adverse events of special interest (AESI)
Time frame: From the first injection until 1 year after the second injection
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 13 Oct 2026.
- Individual participant dataSharing planned: Undecided
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Sylvain Baize study director
Institut Pasteur
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing Low dose MOPEVAC-Las vaccine, Intermediate dose MOPEVAC-Las vaccine and High dose MOPEVAC-Las vaccine in people with Lassa Fever, run by Institut Pasteur at 1 site in France.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 22 inclusion and 26 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 13 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in France. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Sandrine Fernandes Pellerin (+33145688179, sandrine.fernandespellerin@pasteur.fr), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Rate of solicited and unsolicited Adverse Events (AEs) during the treatment period up to 28 days after each injection. (time frame: From each injection to 28 days later). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 13 Oct 2026.