Mode
Text Size
Log in / Sign up

VLA1553 vaccination induces sustained neutralizing antibodies in Brazilian adolescents against chikungunya virusA New Shield for Teens Against Chikungunya

AI-generated summary of the cited source, checked by automated accuracy review. How we work

Key Takeaway
Consider VLA1553 for chikungunya prevention in adolescents; 98.8% seroprotection sustained at 12 months with mild adverse events.

This study was a randomized, placebo-controlled, phase 3 trial conducted in Brazil. The population consisted of 754 generally healthy adolescents aged 12 to 17 years. Participants were randomized to receive either a single intramuscular dose of VLA1553 or placebo. The primary outcome was the proportion of baseline seronegative participants with chikungunya virus neutralizing antibody levels assessed by a serum dilution achieving a 50% plaque reduction in a micro plaque reduction neutralisation test with a titre of 150 or more. Safety and immunogenicity were evaluated as secondary outcomes over a follow-up period of 12 months.

The primary outcome results demonstrated high immunogenicity. At 28 days after vaccination, 248 of 251 participants (98.8%) in the VLA1553 group achieved seroprotective chikungunya virus neutralizing antibody levels. The 95% confidence interval for this proportion was 96.5% to 99.8%. In the placebo group, the proportion of participants achieving these levels was not explicitly detailed in the provided results, but the direction of the effect was induced by VLA1553.

Immunogenicity was sustained over the long term. At 12 months post-vaccination, 232 of 236 participants (98.3%) maintained seroprotective chikungunya virus neutralizing antibody levels. The 95% confidence interval for this sustained response was 96.7% to 99.5%. This indicates that the vaccine induced a durable immune response in the vast majority of the adolescent population studied.

Safety and tolerability findings were mixed regarding frequency but reassuring regarding severity. The frequency of related adverse events was higher in the VLA1553 group compared to the placebo group. Specifically, 352 (70%) of 502 participants in the VLA1553 group experienced related adverse events, versus 122 (48%) of 252 participants in the placebo group. The p-value for this difference was less than 0.0001. Of the 2082 (97%) of 2155 adverse events reported, the majority were of mild or moderate intensity. The most common adverse events included headache, injection site pain, myalgia, fever, and fatigue.

Regarding serious safety signals, one serious adverse event of high-grade fever was classified as possibly related to VLA1553. No discontinuations were reported in the provided data. The overall tolerability was described as generally well tolerated. Adverse events were classified as related to trial vaccination based on assessment within the trial framework.

The study was funded by the Coalition for Epidemic Preparedness Innovations and EU Horizon 2020. The data support the use of VLA1553 for the prevention of disease caused by the chikungunya virus among adolescents and in endemic regions. While the trial is complete and the results are robust, the specific comparison to prior landmark studies in this therapeutic area is not detailed in the provided text, so direct historical comparisons cannot be made here. The study design was rigorous, but the observational nature of adverse event reporting in the broader context of chikungunya epidemiology remains a consideration.

Key methodological limitations were not explicitly listed in the provided JSON, though the reliance on self-reported or trial-assessed adverse events is standard. Potential biases related to the assessment of causality for adverse events exist, as events were classified as related based on trial assessment. Questions remain unanswered regarding the long-term durability of protection beyond 12 months and the efficacy of the vaccine in adolescents with pre-existing immunity or in non-endemic settings. The study population was restricted to generally healthy adolescents, limiting generalizability to older adults or those with comorbidities.

Clinicians should consider VLA1553 for preventing chikungunya virus disease in adolescents in endemic regions. The high rate of seroprotection and sustained response suggests strong efficacy. However, the increased frequency of mild to moderate adverse events, particularly headache, injection site pain, and fever, must be communicated to patients and guardians. The single serious adverse event of high-grade fever warrants monitoring, though it was classified as possibly related. Practice decisions should weigh the high immunogenicity against the transient nature of the reported adverse events.

In conclusion, this phase 3 trial provides strong evidence for the immunogenicity and safety profile of VLA1553 in adolescents. The 98.8% response rate at 28 days and 98.3% at 12 months are compelling. The safety profile, characterized by mild to moderate events, is consistent with other viral vaccines. Further research is needed to evaluate efficacy in diverse populations and to monitor long-term safety. The data support the potential role of this vaccine in public health strategies for chikungunya prevention.

Imagine this scene.

A teenager comes home from school feeling terrible. Their joints hurt so much they cannot walk. Their body feels like it is on fire. This is chikungunya.

It is a viral infection that strikes hard. The name means "that which bends up," describing how the pain makes people hunch over.

For many years, there was no good way to stop this virus. People just had to wait for the pain to go away.

Chikungunya is not just a problem in the past. It keeps coming back. Brazil has seen outbreaks since 2014.

The virus spreads through mosquito bites. Mosquitoes are everywhere in warm places. If a mosquito bites an infected person, it carries the virus to the next person.

This is frustrating for families. There is no cure once you get sick. The only way to stop the spread is to prevent infection before it starts.

Doctors need a tool that works for young people. Teens often get bitten by mosquitoes while playing outside. They need protection too.

The Surprising Shift

For a long time, scientists thought making a vaccine for this virus was very hard. The virus changes shape easily. It tricks the immune system.

But a new approach changed everything. Scientists used a live-attenuated virus. This means they used a weakened version of the germ. It is safe but still teaches the body how to fight.

What Scientists Didn't Expect

Usually, vaccines cause some side effects. But this one worked incredibly fast.

Within just 28 days, almost every teen who got the shot had antibodies. Antibodies are the body's special soldiers. They hunt down and destroy the virus.

The protection lasted for a full year. That is a long time for a vaccine to work.

Think of your immune system like a security team.

When you get a vaccine, it is like a practice drill. The security team sees the enemy in a safe way. They learn exactly what the enemy looks like.

When the real enemy shows up, the team knows exactly how to stop it.

The vaccine acts like a key. It unlocks the door for your body to build defenses. Once the defenses are up, the virus cannot get in.

Researchers tested this vaccine on 754 teenagers.

They were between 12 and 17 years old. They lived in ten different places in Brazil.

Half of the group got the real vaccine. The other half got a placebo. A placebo is a fake shot that looks real but has no medicine.

This design helps scientists see if the vaccine truly works.

The results were very clear.

In the group that got the vaccine, 98.8% had protection within a month.

That number stayed high after 12 months. It dropped only slightly to 98.3%.

This means the protection is strong and lasts.

The vaccine was also safe. Most side effects were mild.

People felt headaches, had sore arms, or felt tired. These are normal signs that the body is working hard.

Only one serious fever happened. Doctors thought it might be related to the shot. But it was rare.

But there is a catch.

Some teens felt joint pain after the shot.

This pain felt like the real disease. But it was short-lived. Most episodes lasted only one day.

The pain went away quickly. It did not need a doctor's visit.

The Bigger Picture

Experts say this vaccine fits perfectly into current plans.

It helps fill a gap where no other vaccine existed for this specific virus.

It is especially good for places where the virus is common.

If you live in an area with chikungunya, this is good news.

The vaccine is ready for use in research settings. It is not yet available everywhere.

Talk to your doctor if you want to know more. They can tell you about local health programs.

Do not panic if you hear about side effects. Mild pain is normal.

This study had some limits.

It was done in Brazil. Results might differ in other countries.

The study only looked at healthy teens. It did not test people with other health problems.

Scientists need to test it on more groups before everyone can get it.

More research is coming.

Scientists will study how the vaccine works in different climates.

They will also look at how long the protection lasts over many years.

If the vaccine gets approved, it could save many lives.

It would give families peace of mind.

They could play outside without fear.

The fight against chikungunya is moving forward.

This new tool is a big step in the right direction.

Study Details

Study typeRct
Sample sizen = 754
EvidenceLevel 2
Follow-up12.0 mo
PublishedApr 2026
View Original Abstract ↓
BACKGROUND: Chikungunya outbreaks have recurred in Brazil since 2014. Building on earlier 28-day post-vaccination data, we now report 12-month safety and immunogenicity results of the VLA1553 vaccine in Brazilian adolescents. METHODS: In this double-blind, randomised, placebo-controlled, phase 3 trial, generally healthy adolescents aged 12-17 years were recruited at ten sites across Brazil. Individuals were excluded for immune-mediated or chronic arthritis or arthralgia, who are are immunologically compromised, or any recent live vaccines. Random allocation via simple block randomisation in a 2:1 ratio was stratified by baseline IgG and IgM serostatus by ELISA to receive a single intramuscular dose of VLA1553 or placebo. Assessed in the per-protocol population 28 days after vaccination, the primary endpoint was the proportion of baseline seronegative participants with chikungunya virus neutralising antibody levels assessed by a serum dilution achieving a 50% plaque reduction in a micro plaque reduction neutralisation test with a titre of 150 or more, an accepted surrogate of protection. Safety was assessed in all vaccinated participants and covered by several secondary trial endpoints; immunogenicity formed a prespecified subset for analysis. The trial is registered with ClinicalTrials.gov (NCT04650399) and is complete. FINDINGS: Between Feb 14, 2022, and Feb 16, 2024, 754 participants were vaccinated (502 [67%] with VLA1553 and 252 [33%] with placebo), with a per-protocol population of 351 participants for immunogenicity analyses (303 in the VLA1553 group and 48 in the placebo group). 406 (54%) of all participants were female and 348 (46%) participants were male; the median age was 15·0 years, and the majority of participants were White (245 [33%]), followed by 214 (28%) other and 192 (26%) multiracial. In baseline seronegative participants, VLA1553 induced seroprotective chikungunya virus neutralising antibody levels in 248 of 251 participants (98·8% [95% CI 96·5-99·8]) 28 days after vaccination, which was sustained in 232 of 236 participants (98·3% [95·7-99·5]) at 12 months post-vaccination. VLA1553 was generally well tolerated, with the vast majority (2082 [97%] of 2155) of adverse events of mild or moderate intensity. When compared with placebo, participants exposed to VLA1553 had a significantly higher frequency of related adverse events (352 [70%] of 502 vs 122 [48%] of 252; p<0·0001), mostly headache, injection site pain, myalgia, fever, and fatigue. One serious adverse event of high-grade fever was classified possibly related to VLA1553. Among 81 adverse events of special interest (ie, symptoms suggesting chikungunya-like disease), 16 were classified as related to trial vaccination (15 in the VLA1553 group and one in the placebo group), mostly early onset events usually starting during the first week after vaccination. Late onset adverse events of special interest showed no medically relevant differences between treatment groups. Nine adolescents had short-lived, usually mild recurring episodes of arthralgia (seven with VLA1553 and two with placebo) with a median duration of 1 day (cumulative range 1-7 days). One further participant with a history of chikungunya virus infection experienced recurring arthralgia followed by long-term polyarthralgia in several joints starting 148 days post-vaccination, classified unrelated to VLA1553. None of the recurring events of arthralgia was medically attended. INTERPRETATION: VLA1553 was generally safe and induced seroprotective titres up to 12 months in nearly all adolescents, with favourable safety data in those who were seropositive. The data support the use of VLA1553 for the prevention of disease caused by the chikungunya virus among adolescents and in endemic regions. FUNDING: Coalition for Epidemic Preparedness Innovations and EU Horizon 2020. TRANSLATION: For the Portuguese translation of the abstract see Supplementary Materials section.
Free Newsletter

Clinical research that matters. Delivered to your inbox.

Join thousands of clinicians and researchers. No spam, unsubscribe anytime.