A Phase 3 interventional study of Active and Placebo in Chikungunya, sponsored by Butantan Institute. Completed at 10 sites in Brazil. Open to participants aged 12 Years to 17 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-06-04.
Sponsored by Butantan Institute · Phase 3, Interventional, and Prevention
This was a prospective, randomized, double-blinded, multicenter, pivotal study evaluating the full dose of VLA1553 (1 x10E4 TCID50 per dose) in comparison to a placebo control. The dose of VLA1553 or control was administered as single vaccination on Day 1. Overall, approximately 750 male and female participants aged 12 years to \<18 years were enrolled into the study. After completion of the trial, a Post Trial Access program was performed to offer the VLA1553 vaccine to all placebo recipients.
This was a prospective, double-blinded, multicenter, randomized, pivotal Phase 3 study comprising 754 participants aged 12 years to \<18 years randomized in a 2:1 ratio to the live-attenuated CHIKV vaccine candidate (VLA1553) or placebo. The dose of lyophilized VLA1553 or placebo was administered as a single intramuscular vaccination. Subjects in this study were stratified by baseline serostatus. The primary objective of the study was to evaluate the immunogenicity and safety of the full dose of VLA1553 28 days following the single vaccination. Immunogenicity evaluations in the immunogenicity subset included the proportion of subjects with neutralizing CHIKV antibody titers above the seroresponse threshold. The surrogate of protection reasonably likely to predict clinical benefit has been established in non-human primate passive transfer studies using human sera from the Phase 1 study. Safety data collection and immunogenicity were assessed until Month 12.
88 studies on the registry are indexed under Chikungunya Fever; 21 are open to participants now.
This study's enrollment of 754 is above the median of 263 across 57 interventional studies indexed under Chikungunya Fever.
Browse Chikungunya Fever studies →Butantan Institute is the lead sponsor of 31 studies on the registry; 3 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.
for women of :
Exclusion Criteria:
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.
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.
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.
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.
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.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
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.
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.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
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.
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.
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.
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.
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.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis C tests
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
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.
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.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
VLA1553
Biological: Active
Placebo
Biological: Placebo
Single intramuscular vaccination on Day 1 with VLA1553, a lyophilized live-attenuated Chikungunya vaccine candidate 1x10E4 TCID50 per dose (0.5 mL)
Single intramuscular vaccination on Day 1 with Phosphate-Buffered Saline (PBS) as placebo (0.5 mL)
Seroprotection
Percentage of subjects with a seroprotective CHIKV antibody level determined as µPRNT50\>= 150 (Micro Plaque Reduction Neutralization Test 50%) for baseline negative subjects 28 days post-vaccination.
Time frame: On study Day 29,which is 28 days after single vaccination
CHIKV-specific Antibody Titers as GMTs up to 1 Year
Immune response as measured by CHIKV-specific neutralizing antibody titers on Day 1, Day 8, Day 29, Day 85, Day 180 (Month 6) and Day 365 (Month 12) post vaccination as determined by μPRNT
Time frame: On study Day 1, Day 8, Day 29, Day 85, Day 180 (Month 6) and Day 365 (Month 12) post vaccination
Seroprotection up to 1 Year
Percentage of subjects with seroprotective levels defined as μPRNT50 ≥ 150 for μPRNT baseline negative subjects on Day 8, Day 85, Day 180 and Month 12 post-vaccination as determined by μPRNT.
Time frame: On the study Day 8, Day 85, Day 180, and Day 365 (Month 12) after vaccination
Seroconversion up to 1 Year Defined as > 4-fold Increase of μPRNT50 Compared to Baseline
Percentage of subjects with seroconversion defined as \> 4-fold increase of μPRNT50 compared to baseline at Day 29, Month 6 and Month 12 as determined by μPRNT assay
Time frame: On study Day 29, Day 180 and Month 12 after vaccination
Fold Change in Neutralizing Antibodies Compared to Baseline
Fold change of CHIKV-specific neutralizing antibody titers determined by μPRNT assay at Days 8, 29, 85, 180 and at Month 12 post-vaccination as compared to baseline
Time frame: On study Day 8, 29, 85, 180 and Month 12 after vaccination
X-fold Change in Neutralizing Antibody Titers at Month 12 Compared to Baseline
Percentage of subjects reaching an at least 4-fold, 8-fold, 16-fold or 64-fold change in CHIKV-specific neutralizing antibody titer compared to baseline as measured by μPRNT assay
Time frame: 365 days (12 months) after vaccination
Immunogenicity (GMT) Per Baseline Serostatus
CHIKV-specific neutralizing antibodies, determined by μPRNT assay at Days 1, 8, 29, 85, 180, and Month 12 post-vaccination stratified by μPRNT baseline serostatus.
Time frame: On study Day 1, 8, 29, 85, 180 and Month 12 after vaccination
Number of Participants With Unsolicited Adverse Events
Frequency of unsolicited AEs at Day 29 and Day 180 (6 months) post-vaccination
Time frame: On study Day 29 and Day 180 after vaccination
Number of Participants With Solicited Adverse Events
Frequency of solicited injection site and systemic adverse events within ten days post-vaccination
Time frame: up to 10 days after vaccination
Number of Participants With Adverse Event of Special Interest
Frequency of any Adverse Event of Special Interest: The following cluster of symptoms with or without remissions or exacerbations received particular consideration and were defined as early onset AESI: 1. Fever (≥37.8°C measured axillary); and 2. Acute (poly)arthralgia/arthritis, myalgia, neurological symptoms (e.g., meningoencephalitis, acute encephalitis, headache, seizures), retinitis/uveitis; or one or more of the following signs and symptoms: macular to maculopapular rash (sometimes with cutaneous pruritus (foot plant)), pigmentary changes, bullous rash/skin blistering, purpura and ecchymosis; and 3. Onset of symptoms 2 to 21 days after vaccination (i.e., Day 3 to Day 22); and 4. Duration of event ≥3 days, Onset of symptoms 22 days post vaccination or later (Day 23 - study end) was defined as late onset AESI.
Time frame: until 365 days (12 months) after vaccination
Number of Participants With Serious Adverse Events
Frequency and relatedness of any Serious Adverse Event (SAE) during the entire study period
Time frame: until 365 days (12 months) after vaccination
| Milestone | Active | Placebo |
|---|---|---|
| Started | 502 | 252 |
| Completed | 488 | 246 |
| Not completed | 14 | 6 |
Percentage of subjects with a seroprotective CHIKV antibody level determined as µPRNT50\>= 150 (Micro Plaque Reduction Neutralization Test 50%) for baseline negative subjects 28 days post-vaccination.
| participants | Active | Placebo |
|---|---|---|
| Seroprotection | 248 | 1 |
Immune response as measured by CHIKV-specific neutralizing antibody titers on Day 1, Day 8, Day 29, Day 85, Day 180 (Month 6) and Day 365 (Month 12) post vaccination as determined by μPRNT
| titer | Active | Placebo |
|---|---|---|
| Day 1 GMT | 10.6 (10.31 to 10.89) | 11.7 (10.46 to 13.17) |
| Day 8 GMT | 17.6 (15.41 to 20.06) | 10.6 (9.75 to 11.44) |
| Day 29 GMT | 3855.9 (3432.05 to 4331.98) | 12.3 (9.63 to 15.79) |
| Day 85 GMT | 1704.3 (1547.68 to 1876.82) | 10.0 (10.00 to 10.00) |
| Day 180 GMT | 1359.9 (1222.34 to 1512.87) | 10.0 (10.00 to 10.00) |
| Month 12 GMT | 1283.9 (1145.99 to 1438.45) | 10.0 (10.00 to 10.00) |
Percentage of subjects with seroprotective levels defined as μPRNT50 ≥ 150 for μPRNT baseline negative subjects on Day 8, Day 85, Day 180 and Month 12 post-vaccination as determined by μPRNT.
| Participants | Active | Placebo |
|---|---|---|
| Day 8 — Seroprotected | 14 | 0 |
| Day 8 — Non-seroprotected | 231 | 42 |
| Day 85 — Seroprotected | 239 | 0 |
| Day 85 — Non-seroprotected | 2 | 41 |
| Day 180 — Seroprotected | 242 | 0 |
| Day 180 — Non-seroprotected | 3 | 42 |
| Month12 — Seroprotected | 232 | 0 |
| Month12 — Non-seroprotected | 4 | 41 |
Percentage of subjects with seroconversion defined as \> 4-fold increase of μPRNT50 compared to baseline at Day 29, Month 6 and Month 12 as determined by μPRNT assay
| Participants | Active | Placebo |
|---|---|---|
| Day 29 — Seroconversion | 248 | 1 |
| Day 29 — Non seroconversion | 3 | 41 |
| Day 180 — Seroconversion | 243 | 0 |
| Day 180 — Non seroconversion | 2 | 42 |
| Month 12 — Seroconversion | 234 | 0 |
| Month 12 — Non seroconversion | 2 | 41 |
Fold change of CHIKV-specific neutralizing antibody titers determined by μPRNT assay at Days 8, 29, 85, 180 and at Month 12 post-vaccination as compared to baseline
| fold change | Active | Placebo |
|---|---|---|
| Day 8 | 8.18 ± 49.483 | 0.93 ± 0.201 |
| Day 29 | 495.60 ± 379.063 | 4.05 ± 19.660 |
| Day 85 | 202.73 ± 141.663 | 0.90 ± 0.235 |
| Day 180 | 177.17 ± 180.146 | 0.90 ± 0.232 |
| Month 12 | 165.51 ± 147.792 | 0.91 ± 0.215 |
Percentage of subjects reaching an at least 4-fold, 8-fold, 16-fold or 64-fold change in CHIKV-specific neutralizing antibody titer compared to baseline as measured by μPRNT assay
| Participants | Active | Placebo |
|---|---|---|
| 4-fold change - GMT — reached | 234 | 0 |
| 4-fold change - GMT — not reached | 2 | 41 |
| 8-fold change - GMT — reached | 233 | 0 |
| 8-fold change - GMT — not reached | 3 | 41 |
| 16-fold change - GMT — reached | 232 | 0 |
| 16-fold change - GMT — not reached | 4 | 41 |
| 64-fold change - GMT — reached | 194 | 0 |
| 64-fold change - GMT — not reached | 42 | 41 |
CHIKV-specific neutralizing antibodies, determined by μPRNT assay at Days 1, 8, 29, 85, 180, and Month 12 post-vaccination stratified by μPRNT baseline serostatus.
| Titer | Active - Seropositive | Active - Seronegative |
|---|---|---|
| Day 1 | 3097.1 (2324.90 to 4125.89) | 10.6 (10.31 to 10.89) |
| Day 8 | 3251.2 (2458.75 to 4298.98) | 17.6 (15.41 to 20.06) |
| Day 29 | 3886.5 (3063.40 to 4930.87) | 3855.9 (3432.05 to 4331.98) |
| Day 85 | 3913.4 (3015.95 to 5077.91) | 1704.3 (1547.68 to 1876.82) |
| Day 180 | 3736.8 (2848.17 to 4902.71) | 1359.9 (1222.34 to 1512.87) |
| Month 12 | 5048.2 (3931.03 to 6482.89) | 1283.9 (1145.99 to 1438.45) |
Frequency of unsolicited AEs at Day 29 and Day 180 (6 months) post-vaccination
| Participants | Active | Placebo |
|---|---|---|
| Day 29 | 196 | 81 |
| Day 180 | 309 | 148 |
Frequency of solicited injection site and systemic adverse events within ten days post-vaccination
| Participants | Active | Placebo |
|---|---|---|
| Any solicited systemic adverse event | 319 | 107 |
| Headache (Solicited Systemic AE | 256 | 87 |
| Myalgia (Solicited Systemic AE) | 135 | 31 |
| Fatigue (Solicited Systemic AE) | 112 | 24 |
| Fever (Solicited Systemic AE) | 121 | 9 |
| Nausea (Solicited Systemic AE) | 80 | 31 |
| Arthralgia (Solicited Systemic AE) | 65 | 14 |
| Vomiting (Solicited Systemic AE) | 13 | 9 |
| Rash (Solicited Systemic AE) | 18 | 2 |
| Any solicited injection site adverse event | 160 | 62 |
| Tenderness (Solicited Local AE) | 100 | 37 |
| Pain (Solicited Local AE) | 97 | 34 |
| Induration (Solicited Local AE) | 21 | 11 |
| Redness (Solicited Local AE) | 11 | 3 |
| Swelling (Solicited Local AE) | 7 | 7 |
Frequency of any Adverse Event of Special Interest: The following cluster of symptoms with or without remissions or exacerbations received particular consideration and were defined as early onset AESI: 1. Fever (≥37.8°C measured axillary); and 2. Acute (poly)arthralgia/arthritis, myalgia, neurological symptoms (e.g., meningoencephalitis, acute encephalitis, headache, seizures), retinitis/uveitis; or one or more of the following signs and symptoms: macular to maculopapular rash (sometimes with cutaneous pruritus (foot plant)), pigmentary changes, bullous rash/skin blistering, purpura and ecchymosis; and 3. Onset of symptoms 2 to 21 days after vaccination (i.e., Day 3 to Day 22); and 4. Duration of event ≥3 days, Onset of symptoms 22 days post vaccination or later (Day 23 - study end) was defined as late onset AESI.
| Participants | Active | Placebo |
|---|---|---|
| Early Onset AESI | 17 | 2 |
| Late Onset AESI | 38 | 17 |
Frequency and relatedness of any Serious Adverse Event (SAE) during the entire study period
| Participants | Active | Placebo |
|---|---|---|
| Frequency of SAE | 11 | 5 |
| Frequency of related SAE | 1 | 0 |
Collected over up to 10 days after vaccination - Solicited Adverse Events up to 6 months after vaccinattion - Unsolicited Adverse Events up to 12 months after vaccination - Serious Adverse Events and Adverse Event of Special Interest. Non-serious events are listed at a 5% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Active | 0/502 (0%) | 11/502 (2.2%) | 396/502 (78.9%) |
| Placebo | 0/252 (0%) | 5/252 (2%) | 171/252 (67.9%) |
| Event | Active | Placebo |
|---|---|---|
| Transaminase increaseInvestigations | 0/502 | 1/252 |
| Suicidal ideationPsychiatric disorders | 0/502 | 1/252 |
| PneumoniaInfections and infestations | 1/502 | 1/252 |
| Dengue feverInfections and infestations | 0/502 | 1/252 |
| Prothrombin time prolongedInvestigations | 0/502 | 1/252 |
| PharyngitisInfections and infestations | 0/502 | 1/252 |
| Lower limb fractureInjury, poisoning and procedural complications | 1/502 | 0/252 |
| Cat scratch diseaseInfections and infestations | 1/502 | 0/252 |
| PyrexiaGeneral disorders | 1/502 | 0/252 |
| AppendicitisInfections and infestations | 1/502 | 0/252 |
| Event | Active | Placebo |
|---|---|---|
| HeadacheNervous system disorders | 284/502 | 114/252 |
| PyrexiaGeneral disorders | 194/502 | 68/252 |
| MyalgiaMusculoskeletal and connective tissue disorders | 162/502 | 49/252 |
| Injection site painGeneral disorders | 149/502 | 55/252 |
| FatigueGeneral disorders | 117/502 | 30/252 |
| NauseaGastrointestinal disorders | 99/502 | 41/252 |
| ArthralgiaMusculoskeletal and connective tissue disorders | 74/502 | 19/252 |
| OdynophagiaGastrointestinal disorders | 44/502 | 26/252 |
| CoughRespiratory, thoracic and mediastinal disorders | 50/502 | 26/252 |
| VomitingGastrointestinal disorders | 30/502 | 24/252 |
Safety population - All the participants who received the study medication
| Age, Customized(Participants) | Active | Placebo | Total |
|---|---|---|---|
| 12-<15 years | 244 | 129 | 373 |
| 15 - <18 years | 258 | 123 | 381 |
| Sex: Female, Male(Participants) | Active | Placebo | Total |
|---|---|---|---|
| Female | 269 | 137 | 406 |
| Male | 233 | 115 | 348 |
| Ethnicity (NIH/OMB)(Participants) | Active | Placebo | Total |
|---|---|---|---|
| Hispanic or Latino | 358 | 172 | 530 |
| Not Hispanic or Latino | 140 | 79 | 219 |
| Unknown or Not Reported | 4 | 1 | 5 |
| Race (NIH/OMB)(Participants) | Active | Placebo | Total |
|---|---|---|---|
| American Indian or Alaska Native | 2 | 2 | 4 |
| Asian | 2 | 0 | 2 |
| Native Hawaiian or Other Pacific Islander | 0 | 0 | 0 |
| Black or African American | 66 | 31 | 97 |
| White | 167 | 78 | 245 |
| More than one race | 120 | 72 | 192 |
| Unknown or Not Reported | 145 | 69 | 214 |
| Region of Enrollment(Participants) | Active | Placebo | Total |
|---|---|---|---|
| Brazil | 502 | 252 | 754 |
| BMI(Kg/square Meter) | Active | Placebo | Total |
|---|---|---|---|
| Mean | 21.63 ± 4.81 | 21.78 ± 4.75 | 21.68 ± 4.79 |
| Serostatus (PRNT)(Participants) | Active | Placebo | Total |
|---|---|---|---|
| Seronegative μPRNT50<=40 | 408 | 206 | 614 |
| Seropositive μPRNT50>40 | 94 | 45 | 139 |
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: No
Ran from Feb 2022 to primary completion in Mar 2023, 13 months.
Results were first posted in Jun 2026, 3 years 2 months after primary completion.
How these figures are worked out, and which studies are left out of them.
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Butantan Institute