Zika VirusPhase 2NCT04917861
A Study of Zika Vaccine mRNA-1893 in Adult Participants Living in Endemic and Non-Endemic Flavivirus Areas
A Phase 2 study testing mRNA-1893 in people with Zika Virus, run by ModernaTX, Inc. at 11 sites in 2 countries.
Trial summary
This clinical study will evaluate the safety, tolerability, and reactogenicity of 2 dose levels of messenger RNA (mRNA)-1893 Zika vaccine in comparison to a placebo control in healthy participants who are flavivirus-seronegative and in participants who are flavivirus-seropositive. Read more about this study
- Who is it for?
- Ages 18 to 65 yearsHealthy volunteers can take part
- Conditions the study is for
- Zika Virus
- What is being tested?
- mRNA-1893
- Type of treatment
- Vaccines, Injection or infusion
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 808 participants
- Where
- 11 sitesin 2 countries
- Study dates
- 7 Jun 2021to 26 Jul 2024
- Phase
- Phase 2
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
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 65 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Understands and agrees to comply with the study procedures and provides written informed consent.
- According to investigator assessment, is in good general health and can comply with study procedures.
- Female participants of childbearing potential may be enrolled in the study if the participant: has a negative pregnancy test at the Eligibility Visit and on the day of the first investigational product (IP) injection; has practiced adequate contraception or has abstained from all activities that could result in pregnancy for at least 28 days prior to the first IP injection; has agreed to continue adequate contraception through 3 months following the last IP injection; and is not currently breastfeeding.
Who cannot join
- Participant is acutely ill or febrile (temperature ≥38.0°Celsius/100.4°Farenheight) on the day of the first or second vaccination.
- Participant had prior administration of a ZIKV vaccine candidate during a clinical study investigation.
- Participant had prior administration of a marketed dengue vaccine or dengue vaccine candidate under clinical study investigation.
- Participant has a body mass index (BMI) from ≤18 or ≥35 kilograms (kg)/square meter (m^2).
- Participant has a history of myocarditis, pericarditis, or myopericarditis.
- Participant has a history of a diagnosis or condition that, in the judgement of the investigator, is clinically unstable or may affect participant safety, assessment of safety endpoints, assessment of immune response, or adherence to study procedures. "Clinically unstable" is defined as a diagnosis or condition requiring significant changes in management or medication within the 2 months prior to screening and includes ongoing work-up of an undiagnosed illness that could lead to a new diagnosis or condition.
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- Participant has any medical, psychiatric, or occupational condition, including reported history of drug or alcohol abuse, that in the opinion of the investigator, might pose a risk due to participation in the study or could interfere with the interpretation of study results.
- Participant has as a history of anaphylaxis, urticaria, or other significant AR requiring medical intervention after receipt of a vaccine, including an mRNA vaccine or any components of an mRNA vaccine.
- Participant has received or plans to receive a nonstudy vaccine (including authorized or approved vaccines for the prevention of COVID-19) ≤28 days prior to the first IP injection or within 28 days prior to or after any IP injection. Licensed influenza vaccine received within 14 days prior to the first IP injection or plans to receive a licensed influenza vaccine 14 days prior to through 14 days following each IP injection are not exclusionary.
- Participant has received systemic immunoglobulins or blood products within 3 months prior to the day of enrollment.
- Participant has donated ≥450 milliliters (mL) of blood products within 28 days of the Day 1 Visit.
- Participant has participated in an interventional clinical study within 28 days prior to the day of enrollment or plans to do so while enrolled in this study.
Trial locations and contacts
11 sites in 2 countries.
11 sites in 2 countries
Puerto Rico8 sites
Clinical Research Puerto Rico, Inc.
Guayama, PR, 00784
Ponce Medical School Foundation, Inc.
Ponce, PR, 00713
Ponce Medical School Foundation, Inc.
Ponce, PR, 00716
Clinical Research Puerto Rico, Inc.
San Juan, PR, 00909
Latin Clinical Trial Center, Inc.
San Juan, PR, 00909
GCM Medical Group, PSC
San Juan, PR, 00917
Carribean Medical Research
San Juan, PR, 00918
University of Puerto Rico
San Juan, PR, 00935
United States3 sites
Benchmark Research - Fort Worth
Fort Worth, Texas, 76135
Johnson County Clin-Trials
Lenexa, Kansas, 66219
Meridian Clinical Research (Sioux City, IA)
Sioux City, Iowa, 51106
About this study
Official title: A Phase 2, Randomized, Observer-Blind, Placebo-Controlled, Dose Confirmation Study to Evaluate the Safety, Tolerability, and Immunogenicity of Zika Vaccine mRNA-1893 in Adults Aged 18 Through 65 Years and Living in Endemic and Non-Endemic Flavivirus Areas
This clinical study will evaluate the safety, tolerability, and reactogenicity of 2 dose levels of messenger RNA (mRNA)-1893 Zika vaccine in comparison to a placebo control in healthy participants who are flavivirus-seronegative and in participants who are flavivirus-seropositive.
- Conditions
- Zika Virus
- Being tested
- mRNA-1893, Placebo
- Keywords
- Flavivirus, mRNA-1893, Zika vaccine, Moderna
- Medical subject headings
- Zika Virus Infection
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
mRNA-1893Biological
Also called Zika vaccine
Solution for injection
PlaceboBiological
0.9% sodium chloride solution for injection
| Study group | Role | What they receive |
|---|---|---|
| mRNA-1893 Low Dose (2-Dose Regimen) | Experimental | Participants will receive mRNA-1893 at a low dose level administered as a 2-dose regimen with 28-day (-3/+7 days) interval between vaccinations (administered on Day 1 and Day 29). Receives: Biological: mRNA-1893 |
| mRNA-1893 High Dose (2-Dose Regimen) | Experimental | Participants will receive mRNA-1893 at a high dose level administered as a 2-dose regimen with 28-day (-3/+7 days) interval between vaccinations (administered on Day 1 and Day 29). Receives: Biological: mRNA-1893 |
| mRNA-1893 High Dose (1-Dose Regimen) | Experimental | Participants will receive placebo matching to mRNA-1893 on Day 1 and mRNA-1893 at a high dose level administered as a 1-dose regimen (administered on Day 29). There will be 28-day (-3/+7 days) interval between vaccinations. Receives: Biological: mRNA-1893; Biological: Placebo |
| Placebo | Placebo comparator | Participants will receive placebo matching to mRNA-1893 administered as a 2-dose regimen with 28-day (-3/+7 days) interval between vaccinations (administered on Day 1 and Day 29). Receives: Biological: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
Number of Participants With Solicited Local and Systemic Reactogenicity Adverse Reactions (ARs)
Solicited ARs (local and systemic) were collected in the electronic diary. Local ARs included: pain, erythema (redness), swelling/induration (hardness). Systemic ARs included: headache, fatigue, myalgia (muscle aches all over the body), arthralgia (aching in several joints), nausea/vomiting, body temperature (potentially fever), and chills. A summary of all serious adverse events (SAEs) and all nonserious adverse events (AEs) ("Other"), regardless of causality, is in Reported "Adverse Events" section.
Measured: Up to 7 days post-vaccination
Number of Participants With Unsolicited Adverse Events (AEs)
An unsolicited AE was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. Unsolicited AEs were AEs that were not included in the protocol-defined solicited ARs. A treatment-emergent adverse event (TEAE) was defined as any AE not present before exposure to vaccine or any AE already present that worsened in intensity or frequency after exposure. A summary of all SAEs and all nonserious AEs ("Other"), regardless of causality, is located in the Reported "Adverse Events" section.
Measured: Up to 28 days post-vaccination
Number of Participants With Serious Adverse Events (SAEs), AEs of Special Interest (AESIs)
An SAE was defined as any AE that resulted in death, was life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, persistent or significant incapacity or substantial disruption of the ability to conduct normal life functions, was a congenital anomaly/birth defect, or was an important medical event. An AESI was an AE (serious or nonserious) of scientific and medical concern specific to the Sponsor's product or program, for which ongoing monitoring and immediate notification by the Investigator to the Sponsor were required. A summary of all SAEs and all nonserious AEs ("Other"), regardless of causality, is located in the Reported "Adverse Events" section.
Measured: Day 1 through Day 196 for Main Study and Day 197 through Day 700 for Extension Period
Number of Participants With Medically Attended AEs (MAAEs)
An MAAE was an AE that led to an unscheduled visit to a healthcare practitioner. Note that the generation of the tables for the MAAE data for the Main Study occurred after the start of the Extension Period. Therefore, some of the MAAE data for this outcome measure may appear both in the Main Study and the Extension Period. A summary of all SAEs and all nonserious AEs ("Other"), regardless of causality, is located in the Reported "Adverse Events" section.
Measured: Day 1 through Day 196 for Main Study and Day 197 through Day 700 for Extension Period
Geometric Mean Titer (GMT) of Zika Virus (ZIKV)-Specific Neutralizing Antibodies (nAbs) at Day 57, as Measured by 50% Plaque Reduction Neutralization Test (PRNT50)
Antibody values reported as below the lower limit of quantification (LLOQ) were replaced by 0.5 * LLOQ. Values that were greater than the upper limit of quantification (ULOQ) were converted to the ULOQ. LLOQ=91; ULOQ=24814. 95% confidence interval (CI) was calculated based on the t-distribution of the log-transformed values, then back transformed to the original scale for presentation.
Measured: Day 57
GMT of ZIKV-specific nAbs at Day 57, as Measured by 80% Plaque Reduction Neutralization Test (PRNT80)
Antibody values reported as below the LLOQ were replaced by 0.5 * LLOQ. Values that were greater than the ULOQ were converted to the ULOQ. LLOQ=91; ULOQ=24814. 95% CI was calculated based on the t-distribution of the log-transformed values, then back transformed to the original scale for presentation.
Measured: Day 57
Percentage of Participants With Seroconversion at Day 57, as Measured by PRNT50
Seroconversion was defined as an increase in ZIKV-specific nAb titer from below the LLOQ to a titer equal to or above LLOQ, or an increase of at least 4-fold in ZIKV-specific nAb titer in participants with pre-existing nAb titers. LLOQ=91; ULOQ=24814.
Measured: Day 57
Percentage of Participants With Seroconversion at Day 57, as Measured by PRNT80
Seroconversion was defined as an increase in ZIKV-specific nAb titer from below the LLOQ to a titer equal to or above LLOQ, or an increase of at least 4-fold in ZIKV-specific nAb titer in participants with pre-existing nAb titers. LLOQ=91; ULOQ=24814.
Measured: Day 57
Secondary outcomes (12)
GMT of ZIKV-Specific nAbs at Days 1, 8, 29, and 36, as Measured by PRNT50 and PRNT80
Antibody values reported as below the LLOQ were replaced by 0.5 * LLOQ. Values that were greater than the ULOQ were converted to the ULOQ. LLOQ=91; ULOQ=24814. 95% CI was calculated based on the t-distribution of the log-transformed values, then back transformed to the original scale for presentation.
Measured: Days 1, 8, 29, and 36
GMT of ZIKV-Specific nAbs at Days 1, 8, 29, 36, and 57, as Measured by Microneutralization (MN)
Antibody values reported as below the LLOQ were replaced by 0.5 * LLOQ. Values that were greater than the ULOQ were converted to the ULOQ. LLOQ=28; ULOQ=11589. 95% CI was calculated based on the t-distribution of the log-transformed values, then back transformed to the original scale for presentation.
Measured: Days 1, 8, 29, 36, and 57
Geometric Mean Fold Rise (GMFR) of ZIKV-Specific nAbs at Days 8, 29, 36, and 57, as Measured by PRNT50 and PRNT80
Antibody values reported as below the LLOQ were replaced by 0.5 * LLOQ. Values that were greater than the ULOQ were converted to the ULOQ. LLOQ=91; ULOQ=248. 95% CI was calculated based on the t-distribution of the difference in the log-transformed values, then back transformed to the original scale for presentation.
Measured: Days 8, 29, 36, and 57
GMFR of ZIKV-Specific nAbs at Days 8, 29, 36, and 57, as Measured by MN
Antibody values reported as below the LLOQ were replaced by 0.5 * LLOQ. Values that were greater than the ULOQ were converted to the ULOQ. LLOQ=28; ULOQ=11589. 95% CI was calculated based on the t-distribution of the difference in the log-transformed values, then back transformed to the original scale for presentation.
Measured: Days 8, 29, 36, and 57
Percentage of Participants With Seroconversion at Days 8, 29, and 36, as Measured by PRNT50 and PRNT80
Seroconversion was defined as an increase in ZIKV-specific nAb titer from below the LLOQ to a titer equal to or above LLOQ, or an increase of at least 4-fold in ZIKV-specific nAb titer in participants with pre-existing nAb titers. LLOQ=91; ULOQ=24814.
Measured: Days 8, 29, and 36
Percentage of Participants With Seroconversion at Days 8, 29, 36, and 57, as Measured by MN
Seroconversion was defined as an increase in ZIKV-specific nAb titer from below the LLOQ to a titer equal to or above LLOQ, or an increase of at least 4-fold in ZIKV-specific nAb titer in participants with pre-existing nAb titers. LLOQ=28; ULOQ=11589.
Measured: Days 8, 29, 36, and 57
Percentage of Initially Seronegative Participants With a Seroresponse at Days 8, 29, and 36, as Measured by PRNT50 and PRNT80
Seroresponse was defined as an increase in ZIKV-specific nAb titer from below the LLOQ to greater than or equal to the LLOQ. LLOQ=91; ULOQ=24814.
Measured: Days 8, 29, and 36
Percentage of Initially Seronegative Participants With a Seroresponse at Days 8, 29, 36, and 57, as Measured by MN
Seroresponse was defined as an increase in ZIKV-specific nAb titer from below the LLOQ to greater than or equal to the LLOQ. LLOQ=28; ULOQ=11589.
Measured: Days 8, 29, 36, and 57
Percentage of Initially Seropositive Participants With a 2-Fold Increase in ZIKV-Specific nAb Titers as Compared With Baseline, as Measured by PRNT50 and PRNT80
≥2-fold increase from baseline was defined as a ≥2 * LLOQ for participants with baseline undetectable antibody titer, or a 2-times or higher ratio in participants with pre-existing nAb titers. LLOQ=91
Measured: Days 8, 29, 36, and 57
Percentage of Initially Seropositive Participants With a 4-Fold Increase in ZIKV-Specific nAb Titers as Compared With Baseline, as Measured by PRNT50 and PRNT80
≥4-fold increase from baseline was defined as a ≥4 * LLOQ for participants with baseline undetectable antibody titer, or a 4-times or higher ratio in participants with pre-existing nAb titers. LLOQ=91
Measured: Days 8, 29, 36, and 57
Percentage of Initially Seropositive Participants With a 2-Fold Increase in ZIKV-Specific nAb Titers as Compared With Baseline, as Measured by MN
≥2-fold increase from baseline was defined as a ≥2 * LLOQ for participants with baseline undetectable antibody titer, or a 2-times or higher ratio in participants with pre-existing nAb titers. LLOQ=28.
Measured: Days 8, 29, 36, and 57
Percentage of Initially Seropositive Participants With a 4-Fold Increase in ZIKV-Specific nAb Titers as Compared With Baseline, as Measured by MN
≥4-fold increase from baseline was defined as a ≥4 * LLOQ for participants with baseline undetectable antibody titer, or a 4-times or higher ratio in participants with pre-existing nAb titers. LLOQ=28.
Measured: Days 8, 29, 36, and 57
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted8 Jun 2021
- Study start7 Jun 2021
- Primary completion26 Jul 2024
- Study completion26 Jul 2024
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Other trials for Zika VirusStudies of the same condition, open and under way.
- More trials run by ModernaTX, Inc.The 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 2
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 808 participants (actual)
Sponsor and investigators
- Lead sponsor
- ModernaTX, Inc.
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04917861
- Sponsor's protocol ID
- mRNA-1893-P201
- Other IDs
- HHSO100201600029C
- Status last verified
- Aug 2025
- First submitted
- 2 Jun 2021
- Last updated
- 25 Sep 2025
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 25 Sep 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Phase 2, Randomized, Observer-Blind, Placebo-Controlled, Dose Confirmation Study to Evaluate the Safety, Tolerability, and Immunogenicity of Zika Vaccine mRNA-1893 in Adults Aged 18 Through 65 Years and Living in Endemic and Non-Endemic Flavivirus Areas
- ClinicalTrials.gov ID
- NCT04917861
- Acronym / sponsor ID
- mRNA-1893-P201
- Conditions
- Zika Virus
- Keywords
- Flavivirus, mRNA-1893, Zika vaccine, Moderna
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 808 participants (actual)
- Lead sponsor
- ModernaTX, Inc.Industry (pharma, biotech, devices)
- Study start
- 7 Jun 2021 (actual)
- Primary completion
- 26 Jul 2024 (actual)
- Study completion
- 26 Jul 2024 (actual)
- First posted
- 8 Jun 2021 (actual)
- Results
- Posted 25 Sep 2025
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This clinical study will evaluate the safety, tolerability, and reactogenicity of 2 dose levels of messenger RNA (mRNA)-1893 Zika vaccine in comparison to a placebo control in healthy participants who are flavivirus-seronegative and in participants who are flavivirus-seropositive.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 4
| Arm | Type | Receives |
|---|---|---|
| mRNA-1893 Low Dose (2-Dose Regimen) | Experimental | Biological: mRNA-1893Participants will receive mRNA-1893 at a low dose level administered as a 2-dose regimen with 28-day (-3/+7 days) interval between vaccinations (administered on Day 1 and Day 29). |
| mRNA-1893 High Dose (2-Dose Regimen) | Experimental | Biological: mRNA-1893Participants will receive mRNA-1893 at a high dose level administered as a 2-dose regimen with 28-day (-3/+7 days) interval between vaccinations (administered on Day 1 and Day 29). |
| mRNA-1893 High Dose (1-Dose Regimen) | Experimental | Biological: mRNA-1893, Biological: PlaceboParticipants will receive placebo matching to mRNA-1893 on Day 1 and mRNA-1893 at a high dose level administered as a 1-dose regimen (administered on Day 29). There will be 28-day (-3/+7 days) interval between vaccinations. |
| Placebo | Placebo comparator | Biological: PlaceboParticipants will receive placebo matching to mRNA-1893 administered as a 2-dose regimen with 28-day (-3/+7 days) interval between vaccinations (administered on Day 1 and Day 29). |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- Understands and agrees to comply with the study procedures and provides written informed consent.
- According to investigator assessment, is in good general health and can comply with study procedures.
- Female participants of childbearing potential may be enrolled in the study if the participant: has a negative pregnancy test at the Eligibility Visit and on the day of the first investigational product (IP) injection; has practiced adequate contraception or has abstained from all activities that could result in pregnancy for at least 28 days prior to the first IP injection; has agreed to continue adequate contraception through 3 months following the last IP injection; and is not currently breastfeeding.
Key exclusion criteria (12 listed)
- Participant is acutely ill or febrile (temperature ≥38.0°Celsius/100.4°Farenheight) on the day of the first or second vaccination.
- Participant had prior administration of a ZIKV vaccine candidate during a clinical study investigation.
- Participant had prior administration of a marketed dengue vaccine or dengue vaccine candidate under clinical study investigation.
- Participant has a body mass index (BMI) from ≤18 or ≥35 kilograms (kg)/square meter (m^2).
- Participant has a history of myocarditis, pericarditis, or myopericarditis.
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 |
|---|---|---|
| mRNA-1893Also: Zika vaccineSolution for injection | Biological | mRNA-1893 High Dose (1-Dose Regimen), mRNA-1893 High Dose (2-Dose Regimen), mRNA-1893 Low Dose (2-Dose Regimen) |
| Placebo0.9% sodium chloride solution for injection | Biological | Placebo, mRNA-1893 High Dose (1-Dose Regimen) |
Primary outcome
Number of Participants With Solicited Local and Systemic Reactogenicity Adverse Reactions (ARs)
Time frame: Up to 7 days post-vaccination
Solicited ARs (local and systemic) were collected in the electronic diary. Local ARs included: pain, erythema (redness), swelling/induration (hardness). Systemic ARs included: headache, fatigue, myalgia (muscle aches all over the body), arthralgia (aching in several joints), nausea/vomiting, body temperature (potentially fever), and chills. A summary of all serious adverse events (SAEs) and all nonserious adverse events (AEs) ("Other"), regardless of causality, is in Reported "Adverse Events" section.
Number of Participants With Unsolicited Adverse Events (AEs)
Time frame: Up to 28 days post-vaccination
An unsolicited AE was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. Unsolicited AEs were AEs that were not included in the protocol-defined solicited ARs. A treatment-emergent adverse event (TEAE) was defined as any AE not present before exposure to vaccine or any AE already present that worsened in intensity or frequency after exposure. A summary of all SAEs and all nonserious AEs ("Other"), regardless of causality, is located in the Reported "Adverse Events" section.
Number of Participants With Serious Adverse Events (SAEs), AEs of Special Interest (AESIs)
Time frame: Day 1 through Day 196 for Main Study and Day 197 through Day 700 for Extension Period
An SAE was defined as any AE that resulted in death, was life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, persistent or significant incapacity or substantial disruption of the ability to conduct normal life functions, was a congenital anomaly/birth defect, or was an important medical event. An AESI was an AE (serious or nonserious) of scientific and medical concern specific to the Sponsor's product or program, for which ongoing monitoring and immediate notification by the Investigator to the Sponsor were required. A summary of all SAEs and all nonserious AEs ("Other"), regardless of causality, is located in the Reported "Adverse Events" section.
Number of Participants With Medically Attended AEs (MAAEs)
Time frame: Day 1 through Day 196 for Main Study and Day 197 through Day 700 for Extension Period
An MAAE was an AE that led to an unscheduled visit to a healthcare practitioner. Note that the generation of the tables for the MAAE data for the Main Study occurred after the start of the Extension Period. Therefore, some of the MAAE data for this outcome measure may appear both in the Main Study and the Extension Period. A summary of all SAEs and all nonserious AEs ("Other"), regardless of causality, is located in the Reported "Adverse Events" section.
Geometric Mean Titer (GMT) of Zika Virus (ZIKV)-Specific Neutralizing Antibodies (nAbs) at Day 57, as Measured by 50% Plaque Reduction Neutralization Test (PRNT50)
Time frame: Day 57
Antibody values reported as below the lower limit of quantification (LLOQ) were replaced by 0.5 * LLOQ. Values that were greater than the upper limit of quantification (ULOQ) were converted to the ULOQ. LLOQ=91; ULOQ=24814. 95% confidence interval (CI) was calculated based on the t-distribution of the log-transformed values, then back transformed to the original scale for presentation.
GMT of ZIKV-specific nAbs at Day 57, as Measured by 80% Plaque Reduction Neutralization Test (PRNT80)
Time frame: Day 57
Antibody values reported as below the LLOQ were replaced by 0.5 * LLOQ. Values that were greater than the ULOQ were converted to the ULOQ. LLOQ=91; ULOQ=24814. 95% CI was calculated based on the t-distribution of the log-transformed values, then back transformed to the original scale for presentation.
Percentage of Participants With Seroconversion at Day 57, as Measured by PRNT50
Time frame: Day 57
Seroconversion was defined as an increase in ZIKV-specific nAb titer from below the LLOQ to a titer equal to or above LLOQ, or an increase of at least 4-fold in ZIKV-specific nAb titer in participants with pre-existing nAb titers. LLOQ=91; ULOQ=24814.
Percentage of Participants With Seroconversion at Day 57, as Measured by PRNT80
Time frame: Day 57
Seroconversion was defined as an increase in ZIKV-specific nAb titer from below the LLOQ to a titer equal to or above LLOQ, or an increase of at least 4-fold in ZIKV-specific nAb titer in participants with pre-existing nAb titers. LLOQ=91; ULOQ=24814.
12 secondary outcomes
GMT of ZIKV-Specific nAbs at Days 1, 8, 29, and 36, as Measured by PRNT50 and PRNT80
Time frame: Days 1, 8, 29, and 36
GMT of ZIKV-Specific nAbs at Days 1, 8, 29, 36, and 57, as Measured by Microneutralization (MN)
Time frame: Days 1, 8, 29, 36, and 57
Geometric Mean Fold Rise (GMFR) of ZIKV-Specific nAbs at Days 8, 29, 36, and 57, as Measured by PRNT50 and PRNT80
Time frame: Days 8, 29, 36, and 57
GMFR of ZIKV-Specific nAbs at Days 8, 29, 36, and 57, as Measured by MN
Time frame: Days 8, 29, 36, and 57
Percentage of Participants With Seroconversion at Days 8, 29, and 36, as Measured by PRNT50 and PRNT80
Time frame: Days 8, 29, and 36
Percentage of Participants With Seroconversion at Days 8, 29, 36, and 57, as Measured by MN
Time frame: Days 8, 29, 36, and 57
Percentage of Initially Seronegative Participants With a Seroresponse at Days 8, 29, and 36, as Measured by PRNT50 and PRNT80
Time frame: Days 8, 29, and 36
Percentage of Initially Seronegative Participants With a Seroresponse at Days 8, 29, 36, and 57, as Measured by MN
Time frame: Days 8, 29, 36, and 57
Percentage of Initially Seropositive Participants With a 2-Fold Increase in ZIKV-Specific nAb Titers as Compared With Baseline, as Measured by PRNT50 and PRNT80
Time frame: Days 8, 29, 36, and 57
Percentage of Initially Seropositive Participants With a 4-Fold Increase in ZIKV-Specific nAb Titers as Compared With Baseline, as Measured by PRNT50 and PRNT80
Time frame: Days 8, 29, 36, and 57
Percentage of Initially Seropositive Participants With a 2-Fold Increase in ZIKV-Specific nAb Titers as Compared With Baseline, as Measured by MN
Time frame: Days 8, 29, 36, and 57
Percentage of Initially Seropositive Participants With a 4-Fold Increase in ZIKV-Specific nAb Titers as Compared With Baseline, as Measured by MN
Time frame: Days 8, 29, 36, and 57
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 25 Sep 2025.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
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Enrolling by invitationObservational study
Neurodevelopmental Outcomes in ZIKV-Exposed Children
Zika Virus, Congenital Zika Syndrome
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. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
11 sites in 2 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing mRNA-1893 in people with Zika Virus, run by ModernaTX, Inc. at 11 sites in 2 countries.
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 3 inclusion and 12 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: finished, as of the sponsor's last update on 25 Sep 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 11 sites in Puerto Rico, United States. 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. Some participants in this study may receive a placebo. 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 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
Yes. Results are posted in the registry (first posted 25 Sep 2025). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Number of Participants With Solicited Local and Systemic Reactogenicity Adverse Reactions (ARs) (time frame: Up to 7 days post-vaccination). The study lists 8 primary outcomes in all. 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 25 Sep 2025.