99 percent of vaccinated adults maintained high antibody levels after one year
As chikungunya continues its rapid spread through Brazil and the Americas, a single-dose vaccine developed by Valneva and Instituto Butantan has demonstrated that immune protection endures well beyond the moment of injection — with 99 percent of trial participants still carrying high antibody levels a full year after vaccination. This durability, consistent even among older adults, marks a meaningful step in the long human effort to outpace a virus that travels on the wings of the same mosquito responsible for dengue and Zika. With Brazil recording over 170,000 probable cases and 85 deaths in 2022 alone, the science arrives not as an abstraction but as an answer to an urgent and growing need.
- Chikungunya cases in Brazil surged 80% in 2022 compared to the prior year, with 85 confirmed deaths and 20 more under investigation — a crisis demanding faster solutions.
- A year-long follow-up of trial participants revealed that 99% still carried strong antibody protection, including adults over 65, silencing early doubts about the vaccine's staying power.
- Valneva was racing toward an FDA approval submission by the end of 2022, positioning the shot as the first licensed defense against a virus that has long gone unanswered.
- A parallel Brazilian trial launched in January 2022 is testing the vaccine in 750 adolescents — including those who have already survived infection — to determine whether prior exposure alters the immune response.
- The single-dose design, achieved by deleting a portion of the virus's genetic code, offers a logistical advantage that could prove critical in regions where healthcare access is already strained.
A single-dose chikungunya vaccine developed by Valneva and Brazil's Instituto Butantan has shown that the immune protection it generates does not fade quickly. Researchers following 363 adults for twelve months after vaccination found that 99 percent still carried high antibody levels at the one-year mark — a result that held steady across age groups, including those over 65. The finding builds on an earlier late-stage trial in the United States, where 96 percent of 4,115 participants produced antibodies within six months of their shot.
The vaccine uses a weakened, modified form of the chikungunya virus — one whose ability to infect human cells has been removed by deleting part of its genetic code. The single-injection design is a practical advantage in regions where multi-dose schedules are difficult to complete. Valneva's medical director expressed confidence that the vaccine could meet what the company described as a significant and growing public health threat, with an FDA approval application expected by the close of 2022.
The urgency behind that timeline is visible in Brazil's numbers. By late November 2022, the country had logged more than 170,000 probable chikungunya cases — an 80 percent increase over the same period in 2021 — along with 85 deaths and 20 more under investigation. The disease spreads through Aedes aegypti, the same mosquito that carries dengue and Zika, and brings fever, joint pain, rashes, and headaches to those it infects.
A separate Brazilian clinical trial, running in parallel since January 2022, is enrolling 750 adolescents across ten research centers to study the vaccine's safety and immune response in younger people — including those who have already had the disease. Over fifteen months, researchers will examine whether a prior infection changes how the vaccine performs, extending the evidence base beyond the adult population studied in the United States.
A single dose of chikungunya vaccine kept antibody levels high for a full year in nearly all people who received it—a finding that adds weight to what researchers already knew about the shot's safety and ability to trigger an immune response. The vaccine, developed by the pharmaceutical company Valneva in partnership with Brazil's Instituto Butantan, represents the first real hope for preventing infection from a virus that has been spreading rapidly across the Americas.
The vaccine works by using a weakened form of the virus itself, stripped of its ability to infect human cells. Valneva achieved this by deleting a portion of the pathogen's genetic code. The design calls for just one injection—a significant advantage over vaccines requiring multiple doses. In March of this year, a late-stage clinical trial involving 4,115 participants in the United States showed that 96 percent of them produced antibodies against chikungunya within six months of vaccination.
But the real test was durability. Researchers followed 363 of those adults for a full year after their single shot. When they checked antibody levels at the twelve-month mark, 99 percent of participants still had high levels of immune protection. Notably, this persistence held steady across age groups—people over 65 maintained antibody levels just as well as younger adults did. The company called the results confirmation of what earlier studies had suggested: the antibodies stick around.
Valneva was working toward submitting its application for approval to the FDA by the end of 2022. If granted, the vaccine would address what the company described as a significant and growing public health threat. Juan Carlos Jaramillo, the company's medical director, said in a statement that they were confident the vaccine could help confront this expanding and largely unmet danger.
The urgency is real. Chikungunya spreads through the same mosquito—Aedes aegypti—that carries dengue and Zika. The infection brings fever, red rashes, joint pain, and headaches. In Brazil alone, the numbers tell a stark story. By late November 2022, the country had recorded more than 170,000 probable cases since the start of the year, an 80 percent jump compared to the same stretch in 2021. The death toll stood at 85, with another 20 deaths still under investigation.
Parallel to the American trial, a Brazilian clinical study began in January 2022 with a different focus. Working with Instituto Butantan, researchers are testing the vaccine in 750 adolescents across ten research centers nationwide. This trial will run for fifteen months and will measure both safety and immune response in young people who have already had chikungunya and those who have never been infected. The question is whether prior exposure changes how the vaccine works—and whether it works equally well in teenagers as it did in the adults tested in the United States.
Citas Notables
These antibody levels confirm the antibody persistence profile observed in earlier studies— Valneva, in official statement
If our experimental vaccine is approved, we are confident it can help address this large, growing, and unmet public health threat— Juan Carlos Jaramillo, medical director of Valneva
La Conversación del Hearth Otra perspectiva de la historia
Why does it matter that antibodies persist for a full year? Couldn't they drop off after that?
That's the real question. We don't know yet what happens after twelve months. But the fact that 99 percent of people still had high levels at one year is a strong signal. It suggests the immune system has "remembered" the virus. If protection holds for years, you might only need one shot in your lifetime.
The vaccine uses a weakened virus. How is that different from other approaches?
Some vaccines use just a piece of the virus, or genetic instructions to make a piece. This one uses the whole virus, but crippled—it can't actually infect you. That approach can sometimes trigger a stronger, more complete immune response because your body sees the whole target.
Brazil is in the middle of an outbreak. Why is the local trial focused on adolescents?
They're testing whether the vaccine works differently in people who've already had the disease. If you've been infected once, your immune system has already met the virus. Adding a vaccine might boost that memory, or it might work differently than in someone who's never seen it. That's crucial information for a country where the virus is already circulating.
What happens if the FDA approves this but the Brazilian trial shows a problem?
That would be a real complication. The FDA approval would be based on the American data. But if the Brazilian trial finds something unexpected in adolescents—say, a safety issue or poor immune response—that could change how the vaccine is used in Brazil, even if it's approved elsewhere.