IXCHIQ® Chikungunya Vaccine (VLA1553) Clinical Trials, Dosage, Efficacy, Indication, Side Effects
Valneva SE's IXCHIQ® Chikungunya Vaccine, Live (VLA1553) is the first approved monovalent, single-dose, live-attenuated vaccine. As of 2023, IXCHIQ® was the first vaccine approved to address chikungunya virus (CHIKV) infections in adults at increased risk of exposure to the mosquito-transmitted disease. IXCHIQ is based on an infectious clone (CHIKV LR2006-OPY1) that has been attenuated by deleting a significant gene encoding the non-structural replicase complex protein nsP3, thereby protecting against various Chikungunya virus (CHIKV) phylogroups and strains. IXCHIQ is designed for prophylactic and active immunization against CHIKV infections in individuals aged 1 year and above. Recombumin®, a chemically defined, human and animal origin-free recombinant human albumin, enables the manufacture and formulation of IXCHIQ.
IXCHIQ was approved by the U.S. Food and Drug Administration (FDA, STN: 125777) on November 9, 2023. The FDA's Summary Basis for Regulatory Action was posted on December 8, 2023. This indication was approved under FDA-accelerated approval based on anti-CHIKV neutralizing antibody titers. IXCHIQ achieves target immunogenicity with a single dose. Valneva announced on December 3, 2024, that among the 278 healthy adults still enrolled in a clinical trial, 96% maintained neutralizing antibody titers well above the seroresponse threshold three years after receiving a single dose of vaccination. The FDA awarded Valneva a tropical disease priority review voucher under a provision in the FDA Amendments Act of 2007. In 2021, the IXCHIQ vaccine program received FDA Fast Track (2018) and Breakthrough Therapy designations. The FDA published complete prescribing information at this link. The U.S. Defense Health Agency – Immunization Healthcare Division has published guidance authorizing IXCHIQ as a U.S. Department of Defense countermeasure for Chikungunya virus (CHIKV).
On April 16, 2025, the U.S. Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) updated its recommendation for the use of Valneva's IXCHIQ vaccine for preventing disease caused by CHIKV. The ACIP maintained its current recommendation for IXCHIQ for persons aged 18 years or older traveling to a country or territory where a chikungunya outbreak is present. Additionally, IXCHIQ may be considered for persons aged 18 years or older traveling to or taking up residence in a country or territory without an outbreak but with an elevated risk for U.S. travelers, particularly those planning extended travel. The ACIP also noted that for individuals aged 65 years or older, vaccination with IXCHIQ may be indicated in higher-risk settings, such as Réunion Island in France, given the known risks of severe chikungunya disease and hospitalization in this age group.
The ACIP approved recommendations for using IXCHIQ in travelers and laboratory workers in February 2024. On October 23, 2024, the ACIP reviewed an update to IXCHIQ. The long-term persistence clinical trial is ongoing, with a high seroresponse rate of 97% at 2 years. Monitoring will continue for 10 years to determine if a booster dose is needed in the future. The CDC issued an updated Level 2 Travel Health Advisory confirming that chikungunya vaccination is recommended for adults traveling to a destination with a current chikungunya outbreak. On April 16, 2025, the ACIP updated its recommendation for IXCHIQ for adults traveling to a country or territory where a chikungunya outbreak is present, such as Brazil. Additionally, it may be considered for adults traveling to or taking up residence in a country or territory without an outbreak but with an elevated risk for U.S. travelers, particularly when planning extended travel.
On April 1, 2025, Valneva SE announced that the European Commission (EC) has granted marketing authorization in Europe for IXCHIQ to prevent disease caused by the chikungunya virus in individuals 12 years of age and older. IXCHIQ® received European marketing authorization for individuals 18 and older in July 2024. On March 31, 2025, Valneva announced that it submitted a label extension application to the Medicines and Healthcare products Regulatory Agency (MHRA) to expand access to IXCHIQ to include adolescents aged 12 to 17 years in the UK. On April 14, 2025, the Brazilian Health Regulatory Agency (ANVISA) granted marketing authorization for IXCHIQ.
Saint-Herblain, France-based Valneva SE (Nasdaq: VALN; Euronext Paris: VLA) is a specialty vaccine company that provides prevention against diseases with significant unmet medical needs. Valneva's commercial portfolio comprises three travel vaccines: IXIARO/JESPECT, DUKORAL, and IXCHIQ. The Company's 2024 Annual Business Report and 2023 Sustainability Report outline activities and prospective priorities, as mandated by French Decree No. 2017-1265 of August 9, 2017.
On April 23, 2025, Valneva was awarded as Best Biotech of 2025 at the 16th Annual Vaccine Industry Excellence Awards. On April 3, 2024, Valneva announced it had won the Best Prophylactic Vaccine at the Vaccine Industry Excellence Awards 2024. Valneva won the Breakthrough of the Year on June 14, 2024, for its Chikungunya vaccine at the 2024 European Mediscience Awards.
IXCHIQ Vaccine Efficacy
On January 20, 2025, Valneva SE reported IXCHIQ® showed a sustained 98.3% sero-response rate one year after a single vaccination. The Lancet Infectious Diseases published results from a phase 3b study, concluding that after a single dose of VLA1553, Chikungunya virus-neutralizing antibodies remained above the threshold considered protective and persisted for up to two years. There were no long-term serious adverse events related to vaccination. Valneva announced its presence at the forthcoming 25th World Vaccine Congress, scheduled to take place from April 21 to 24, 2025.
IXCHIQ Vaccine Availability
As of April 18, 2025, IXCHIQ was available for adults in the United States, Asia, Canada, Europe, the United Kingdom, and the Virgin Islands. To date, Valneva has supplied approximately 80,000 doses of IXCHIQ.
On May 31, 2024, the European Commission (EMA/271910/2024) recommended the vaccine. The UK's Medicines and Healthcare Products Regulatory Agency approved IXCHIQ to protect adults against chikungunya disease. On December 19, 2024, Valneva SE and Serum Institute of India (SII) announced an exclusive license agreement to supply IXCHIQ in Asia. As of 2025, the Brazilian Health Regulatory Agency (Anvisa) is reviewing IXCHIQ's marketing application. To make the vaccine more accessible to Low- and Middle-Income Countries, Valneva and Instituto Butantan in Brazil signed an agreement in January 2021 to develop, manufacture, and market VLA1553.
On March 24, 2025, Valneva announced an agreement, supported by the local public health agency, Agence Régionale de Santé La Réunion, to provide 40,000 vaccine doses starting on April 7, 2025, with an option to supply additional doses. This supply of doses, paid for by the French authorities, aligns with the recommendation of France's national public health agency, the Haute Autorité de Santé, to prioritize vaccination for adults aged 65 and over with comorbidities. IXCHIQ remains available for purchase in France, on the mainland, and overseas.
IXCHIQ Vaccine CHIKV Cross-Neutralization
A Research Article published on March 10, 2025, analyzed the plaque reduction neutralization of three CHIKV lineages: the East Central South African, West African, and Asian lineages. These lineages were inhibited by CHIKV-specific neutralizing antibodies present in sera from vaccinated humans. This effect was independent of the time elapsed since vaccination. Moreover, the magnitude of the immune response was similar to the antibody levels detected in sera from convalescent chikungunya patients.
IXCHIQ Vaccine U.S. CDC Reviews
The U.S. CDC website says the agency is currently investigating hospitalizations for cardiac or neurologic events following vaccination with IXCHIQ among people 65 years of age and older. On June 26, 2024, the U.S. CDC Advisory Committee on Immunization Practices (ACIP) reviewed the following presentations on IXCHIQ and Chikungunya virus. On February 28, 2024, the ACIP reviewed Key points from the FDA licensure and package insert, as well as a review of proposed policy options for chikungunya vaccine use among U.S. adults traveling abroad, laboratory workers, and pregnant and breastfeeding women. On February 29, 2024, Valneva SE announced that the ACIP voted to recommend the use of IXCHIQ® for the prevention of diseases caused by CHIKV.
Dr. Beth Bell presented proposed policy options for the use of a chikungunya vaccine among U.S. adults traveling abroad at the ACIP meeting on October 26, 2023. On June 22, 2023, the ACIP reviewed the following presentations: ACIP Work Group timeline (tentative) and the value of a vaccine to prevent travel-related Chikungunya for U.S. persons. On February 23, 2023, the ACIP presentations included: Introduction by Dr. Beth Bell; Global Epidemiology of Chikungunya, presented by Dr. Susan Hills; Chikungunya in U.S. travelers, presented by Ms. Nicole Lindsey; Persistent arthralgiaChikungunyaChikungunya, also presented by Ms. Nicole Lindsey; and Workgroup considerations, also presented by Ms. Nicole Lindsey. During the ACIP meeting on October 19, 2022, Katrin Dubischar, VP and Program Director of the Chikungunya Vaccine, delivered the introduction to the VLA1553 Chikungunya Vaccine Candidate, Evidence Supporting the Serological Endpoint, and an overview of the clinical study. VLA1553 is an efficient and safe intervention that offers high seroprotection against chikungunya virus infection. This virus is likely to spread globally and has an urgent demand for long-lasting prophylaxis.
The U.S. CDC has published recommendations for using the Chikungunya vaccine among adult travelers. The ACIP recommends the Chikungunya vaccine for individuals aged 18 years or older who are traveling to a country or territory with a Chikungunya outbreak. Additionally, the Chikungunya vaccine may be considered for individuals traveling to a country or territory without an outbreak but with evidence of Chikungunya virus transmission among humans within the past five years. Persons aged 65 years or older, particularly those with underlying medical conditions, are likely to have at least moderate exposure* to mosquitoes or those staying for a cumulative period of 6 months or more. Moderate exposure could include travelers with at least two weeks (cumulative) of exposure to mosquitoes in indoor or outdoor settings.
IXCHIQ Vaccine Pediatric Efficacy
On January 22, 2025, Valneva announced that VLA1553-221 met its primary endpoint, demonstrating that the vaccine was well tolerated by children aged one to eleven years, regardless of the dose (half dose or full dose) or previous CHIKV infection, and, to a similar extent, by an active control MenACYW vaccine. Overall, the safety profile was consistent with the profile observed in Valneva's pivotal Phase 3 trials in adults and adolescents. An independent Data Safety Monitoring Board confirmed the absence of any safety concerns. Valneva's vaccine was highly immunogenic in both dose groups. A full dose of the vaccine elicited a more robust immune response than a half dose, as evidenced by protective antibody titers already present at Day 15 and Day 29, confirming Immunogenicity previously observed in adults and adolescents.
On January 10, 2024, Valneva announced that the first participant had been vaccinated in a Phase 2 clinical immunogenicity study evaluating the safety and Immunogenicity of two different doses of Valneva's single-shot chikungunya vaccine in children. On December 4, 2023, Valneva reported a 97% seroresponse rate 24 months after a single vaccination with IXCHIQ and no safety concerns. On November 13, 2023, Valneva reported positive pivotal Phase 3 immunogenicity data in adolescents. VLA1553, administered as a single dose, was generally well tolerated in adolescents aged 12 to 18 years, regardless of previous CHIKV infection, and exhibited a safety profile similar to that reported in adults. These results complement the initial Phase 3 safety data the Company reported for the trial in August 2023.
IXCHIQ Vaccine Indication
The U.S. CDC recommends vaccination for adults aged 18 years and older traveling to a country with a chikungunya outbreak. XCHIQ targets long-term protection against the Chikungunya virus in adults following immunization. However, vaccination with IXCHIQ may not protect all individuals. In Europe, IXCHIQ is authorized for individuals 12 years and older.
Over 50 million North Americans, including approximately 7 million Canadians, travel to areas where Chikungunya is endemic. While the incidence of Chikungunya CHIKV infection is low, the morbidity and overall burden of the disease are high. A study reported in December 2024 found that Chikungunya chronic arthralgia has a significant impact on long-term health and work.
IXCHIQ Vaccine Dosage
VLA1553 is administered intramuscularly with a single dose. At clinical trial centers in Illinois and Alabama, U.S., healthy volunteers aged 18–45 years were randomly assigned (1:1:2) to one of three escalating groups (low dose 3·2 × 10^3 per 0·1 mL; medium dose 3·2 × 10^4 per 1 mL; or high-dose 3·2 × 10^5 50% tissue culture infection dose per 1 mL) and received a single-shot immunization on day 0. Individuals in all groups were revaccinated with the highest dose at either month 6 or 12 and followed for 28 days after revaccination.
IXCHIQ Vaccine Contraindications
IXCHIQ® should not be given to individuals who have a weakened immune system due to medications used for hematologic and solid tumors, are on chemotherapy, have a history of congenital immunodeficiency, are under long-term immunosuppressive therapy, or have an HIV infection and are severely immunocompromised—individuals with a history of a severe allergic reaction to any vaccine component.
IXCHIQ Vaccine Warnings
On October 14, 2024, a study concluded, 'A single dose of VLA1553 presented with an excellent local tolerability profile and overall safety in line with that expected for a live-attenuated vaccine.' Common adverse reactions following vaccination, which occurred in more than 10% of vaccinated individuals in clinical trials, included tenderness, headache, fatigue, myalgia, arthralgia, fever, and nausea. IXCHIQ also caused severe or prolonged chikungunya-like adverse reactions in some persons. Appropriate medical treatment to manage immediate allergic reactions for acute anaphylactic reactions following the administration of IXCHIQ® or any vaccine must be available, says the FDA. Vaccination with IXCHIQ® may cause severe or prolonged chikungunya-like adverse reactions. Severe chikungunya-like adverse reactions that prevented daily activity and/or required medical intervention occurred in 1.6% of 3,082 IXCHIQ® recipients and no placebo recipients. Fourteen IXCHIQ® recipients had prolonged (duration at least 30 days) chikungunya-like adverse reactions. The most common injection site reaction (>10%) was tenderness (11%), and the most common systemic adverse reactions (>10%) were headache (31%), fatigue (29%), myalgia (24%), arthralgia (17%), fever (13%) and nausea (11%)
IXCHIQ Vaccine Pregnancy And Lactation
There are no adequate and well-controlled studies of IXCHIQ in pregnant individuals, and the available human data from clinical trials with IXCHIQ are insufficient to establish whether the vaccine poses any risks during pregnancy. In general, vaccination should be deferred until after delivery. However, if pregnant women choose to be vaccinated, out of caution, vaccination should generally be avoided during the 1st trimester (until 14 weeks of gestation) and after the 36th week of gestation. A developmental study was conducted on female rats. IXCHIQ® should be administered during pregnancy only after an individual risk-benefit assessment, considering the maternal risk of chikungunya infection and gestational age. Vertical transmission of wild-type CHIKV to neonates from pregnant women with viremia at delivery is standard and can cause severe, potentially fatal CHIKV disease in neonates. Human data are not available to assess the impact of IXCHIQ on milk production, its presence in breast milk, or its effects on the breastfed child.
IXCHIQ Immunocompromised Individuals
Due to disease or medical therapy, IXCHIQ should not be administered to individuals with immunodeficiency or immunosuppression.
IXCHIQ Vaccine Efficacy Against Alphaviruses
Alphaviruses are vector-borne, medically relevant, positive-stranded RNA viruses that cause human disease worldwide. A study published on August 7, 2024, characterized neutralizing antibodies (nAbs) against Chikungunya virus (CHIKV) strains. IXCHIQ elicited 100% seroconversion to each virus, except for RRV at 83.3% seroconversion of vaccinees, and cross-neutralizing antibody potency decreased with increasing genetic distance from CHIKV. These data suggest that IXCHIQ efficiently and potently elicits cross-neutralizing antibody (nAb) breadth that extends to related alphaviruses, similar to natural CHIKV infection. The journal Science Translational Medicine published a Research Article, Vol. 15, Issue 696, on May 17, 2023, which found that MAbs with the most significant passive protective efficacy in a mouse model of CHIKV also protected against related arthritogenic alphaviruses.
IXCHIQ Vaccine Coadministration
The Company has not disclosed coadministration information.
IXCHIQ Vaccination for Laboratory Staff
According to the CDC, chikungunya vaccination is recommended for laboratory workers who may be at risk of exposure to the virus. Transmission of the virus through the aerosol and percutaneous routes has been documented in laboratory settings, and accidental mucosal exposure is a potential risk. Laboratory work with the Chikungunya virus is restricted to biosafety level-3 (BSL-3) facilities and practices.
Chikungunya Outbreaks
Countries in Asia, Europe, and the Americas reported Chikungunya virus outbreaks in 2023, 2024, and 2025.
Valneva SE Agreements with CEPI
The Coalition for Epidemic Preparedness Innovations (CEPI) and Valneva SE announced on July 22, 2024, that they have expanded their partnership to support broader access to IXCHIQ in low- and Middle-Income countries (LMICs), as well as post-marketing trials and potential label extensions in children, adolescents, and pregnant women. CEPI will provide Valneva up to U.S. $41.3 million of additional funding over the next five years, with support from the European Union's (EU) Horizon Europe program. An earlier CEPI agreement awarded Valneva U.S. $24.6 million in CEPI-EU funding to develop, manufacture, and market its single-shot vaccine, particularly for low- and middle-income countries (LMICs) in the context of Chikungunya.Chikungunya Financial News
Valneva SE filed its 2024 Universal Registration Document with the French Financial Markets Authority on March 24, 2025, under filing number D.25-0140, and its Form 20-F with the U.S. Securities and Exchange Commission on the same date.
Valneva announced in March 2025 that total product sales reached €163.3 million in 2024, compared to €144.6 million in 2023.
Valneva and the Butantan Institute in Brazil signed a term sheet in May 2020 to develop, manufacture, and market VLA1553. The collaboration is part of the $23.4 million funding framework that Valneva received from CEPI in July 2019 to make VLA1553 accessible to low- and Middle-Income Countries. As of July 22, 2024, Valneva will receive up to $41.3 million from CEPI and the European Union. On February 5, 2025, CEPI reaffirmed its commitment to expanding access to affordable vaccine doses in endemic regions.
IXCHIQ Vaccine News
April 18, 2025 - Juan Carlos Jaramillo, M.D., Chief Medical Officer of Valneva, commented in a press release, "Valneva is committed to the highest standards of safety, and the safety profile of IXCHIQ® remains unchanged and positive. We respect the ACIP recommendation and agree on the importance of continuing the stringent safety surveillance protocols that are in place. We encourage providers to assess the benefit/risk of vaccination based on the individual's medical history and upcoming travel, in line with the current recommendation."
April 14, 2025 - Dr. Esper Kallás, Director of Instituto Butantan, stated, "The approval of the chikungunya vaccine is a great victory for Brazil, where over 150,000 people suffer from the disease yearly. It is an honor for Butantan to be able to contribute to ensuring that this vaccine reaches the population that needs it the most."
April 1, 2025 - Dr. Richard Hatchett, Chief Executive Officer of the Coalition for Epidemic Preparedness Innovations, commented, "EC's marketing authorization for use of IXCHIQ® in adolescents in the EU is an important steppingstone that could help accelerate the approval of the vaccine in this age group in other regions, including areas where the disease is endemic."
February 28, 2025 - Juan Carlos Jaramillo, M.D., Chief Medical Officer of Valneva, stated, "Broader accessibility will help provide protection and mitigate the burden of this debilitating illness, which continues to spread in previously unaffected areas."
February 25, 2025 - The CDC investigates hospitalizations for cardiac or neurologic events following vaccination with IXCHIQ.
February 18, 2025: Peter BühlValneva'sva's Chief Financial Officer, commented, "Once again, we successfully delivered double-digit sales growth... We made significant clinical and regulatory progress last year, setting the stage for several important catalysts to drive value in 2 "25."
February 4, 2025: Julian Beach, MHRA Interim Executive Director of Healthcare Quality and Access, said in a press release, "Patient safety is our top priority, which is why I am pleased to confirm the approval of the first vaccine in the UK to protect adults 18 years and older against Chikungunya."
January 22, 2025 - Juan Carlos Jaramillo, M.D., Chief Medical Officer of Valneva, stated, "These initial data in children are consistent with the robust antibody response and favorable safety profile we reported in both adolescents and adults after a single vaccination."
December 3, 2024—Juan Carlos Jaramillo, M.D., Chief Medical Officer of Valneva, said in a press release, "We are extremely pleased about these three-year data, which further highliIXCHIQ®'sQ®'s differentiated product profile and ability to induce a robust, long-lasting antibody response in both younger and older adults with a single vaccination.
September 4, 2024: The Lancet published a Comment stating that an effective chikungunya vaccine would reduce the burden of acute infections and mitigate the substantial loss of economic productivity in working-age adults.
July 22, 2024—Thomas Lingelbach, Chief Executive Officer of Valneva, said, "We are extremely pleased to strengthen our partnership with CEPI." Valneva will receive up to $41.3 million from CEPI and the European Union to expand access to the chikungunya vaccine, IXCHIQ®.
July 1, 2024: Dr. Richard Hatchett, CEO of the Coalition for Epidemic Preparedness Innovations, comments, "Supported by CEPI and EU funding, IXCHIQ is the world's first vaccine offering protection against the debilitating CHIKV."
May 21, 2024 – Valneva SE announced the appointment of Dr. Hanneke Schuitemaker, Ph.D., as Chief Scientific Officer and Executive Committee member, effective June 3, 2024.
January 10, 2024 - Juan Carlos Jaramillo, M.D., Chief Medical Officer of Valneva, said, "This pediatric clinical trial is significant. Given the significant threat that Chikungunya poses to individuals living in or traveling to endemic areas, it is crucial to make the vaccine accessible to all age groups."
October 19, 2022 - The U.S. CDC vaccine committee reviews various presentations, including "Overview of Chikungunya and Chikungunya Vaccines" by Susan Hills, MBBS, MTH, CDC Lead of the Chikungunya Vaccines Work Group.
July 7, 2021 - Valneva SE announced that the U.S. FDA had awarded Breakthrough Therapy Designation for VLA1553.
January 25, 2021: Valneva SE and Instituto Butantan signed definitive agreements to develop, manufacture, and market Valneva's single-shot chikungunya vaccine, VLA1553, in Low —and Middle-Income Countries.
October 16, 2020 - Valneva SE announced that the European Medicines Agency had granted PRIority Medicines designation for VLA1553.
December 21, 2018 - The U.S. Food and Drug Administration granted VLA1553 Fast Track designation.
VLA-1553 Clinical Trials
Valneva continues to test the VLA1553 Chikungunya Vaccine in various clinical trials.
On June 13, 2023, the phase 3 study results were published: Between September 17, 2020, and April 10, 2021, 6,100 people were screened for eligibility. One thousand nine hundred seventy-two people were excluded, and 4,128 participants were enrolled and randomized (3,093 to VLA1553 and 1,035 to placebo). 358 participants in the VLA1553 group and 133 in the placebo group discontinued the trial before it ended. The per-protocol population for immunogenicity analysis comprised 362 participants (266 in the VLA1553 group and 96 in the placebo group). After a single vaccination, VLA1553 induced seroprotective chikungunya virus-neutralizing antibody levels in 263 (98.9%) of 266 participants in the VLA1553 group (95% CI 96.7–99.8; p < 0.0001) 28 days post-vaccination, independent of age. VLA1553 was generally safe, with an adverse event profile similar to that of other licensed vaccines, and was equally well tolerated in both younger and older adults. Serious adverse events were reported in 46 (1·5%) of 3082 participants exposed to VLA1553 and eight (0·8%) of 1033 participants in the placebo arm. Only two serious adverse events related to VLA1553 treatment (one mild myalgia and one syndrome of inappropriate antidiuretic hormone secretion) were considered. Both participants recovered fully.
VLA1553-301 Phase 3 trial was initiated in September 2020. It is a prospective, double-blinded, multicenter, randomized, pivotal Phase 3 trial evaluating 4,115 participants aged 18 years or above. Lyophilized VLA1553 or placebo was administered as a single intramuscular immunization. The trial's primary objective was to assess the Immunogenicity and safety of VLA1553 in one month following a single vaccination.
Conducted in Brazil by Instituto Butantan, VLA1553-321 is a double-blinded, multicenter, randomized, and placebo-controlled Phase 3 trial. The study will also provide safety and immunogenicity data in participants who have been previously infected with Chikungunya. Chikungunya 2022, Valneva confirmed that the Coalition for Epidemic Preparedness Innovations (CEPI) had funded a Phase 3 clinical study and reported positive topline results from a lot-to-lot manufacturing consistency trial for VLA1553. An analysis announced on March 8, 2022, confirmed the very high level of seroprotection, with 98.9% of participants achieving protective levels of CHIKV-neutralizing antibodies one month after receiving a single vaccination. In addition, the immunogenicity profile was maintained over time, with 96.3% of participants showing protective CHIKV-neutralizing antibody titers six months after receiving a single immunization.
On September 4, 2024, The Lancet published results from a CEPI and EU Horizon 2020-funded phase 3 study conducted in Brazil. The study concluded that VLA1553 was generally safe and induced seroprotective titers in almost all vaccinated adolescents, with favorable safety data in seropositive adolescents at baseline. The data support the use of VLA1553 to prevent diseases caused by the Chikungunya virus among adolescents in endemic areas.
