Could a hantavirus vaccine be on the horizon?
A single shot of an experimental mRNA vaccine completely protected animals against the deadly Andes hantavirus, even at a fraction of the usual dose.
- 17 June 2026
- 5 min read
- by Priya Joi
At a glance
- A new study in The Lancet shows promising results from an experimental vaccine that fully protected animals against Andes hantavirus, one of the few hantaviruses that can spread from person to person.
- Protection held even when the dose was cut to a fraction of the original, which could help stretch limited supplies during an outbreak.
- No vaccine against Andes virus is approved anywhere in the world, although inactivated vaccines for other hantaviruses are used in China and South Korea.
When a rare, lethal virus broke out aboard a cruise ship this May and then scattered across two dozen countries with its passengers, it exposed an uncomfortable gap in the world’s defences: there is no licensed vaccine or treatment for Andes hantavirus.
Now scientists at the University of Texas Medical Branch (UTMB) report that a single dose of an mRNA vaccine gave animals complete protection against the virus.
The finding, published in The Lancet, could offer protection against one of the few hantaviruses able to spread between people.
“Every vaccinated animal remained completely healthy and showed no symptoms or weight loss,” said lead author Dr Michelle Meyer.
“When we looked at the tissues from the vaccinated animals a month after infection, the virus was entirely gone.”
Why the Andes virus worries scientists
Most hantaviruses spread to people through contact with the droppings, urine or saliva of infected rodents.
Andes virus is the exception as it is the only known member of the hantavirus family that can pass from one person to another through close contact with respiratory secretions, such as coughing.
That capacity for spread between people has driven alarming clusters before, explain the authors.
In the paper, they explain how during the 2018 and 2019 outbreak in Epuyén, Argentina, four successive waves of infection traced back to a single social gathering produced 34 confirmed cases and 11 deaths.
The May 2026 outbreak aboard the Dutch cruise ship MV Hondius, which had departed from Argentina, took that threat global. So far it has caused 13 reported cases and three deaths, but the wider worry is what came next.
Nearly 150 passengers dispersed across 23 countries under a patchwork of quarantine rules, all within a virus incubation window that can stretch to 42 days.
Because people can carry the virus without symptoms before they fall ill, tracing everyone who may have been exposed is a daunting task.
Inactivated vaccines against other hantaviruses have been used in China and South Korea for decades.
But none protects against Andes virus, and no hantavirus vaccine of any kind is approved in the Americas or Europe.
With nothing licensed by either the US Food and Drug Administration or the European Medicines Agency, an Andes outbreak is precisely the kind of scenario the UTMB team is racing to prepare for.
One dose, full protection
The researchers had already shown that two of their mRNA vaccine candidates could protect animals against Andes virus, but only after two doses given weeks apart.
An international outbreak that moves fast rarely allows that luxury, so the team set out to test whether a single shot would be enough.
The vaccine uses the same basic design that powered the COVID-19 mRNA shots: genetic instructions that teach the body’s own cells to make harmless pieces of the virus, in this case two surface proteins that train the immune system to recognise and fight the real thing.
The team gave 30 hamsters a single injection of the vaccine, then exposed them to a lethal dose of Andes virus four weeks later.
This hamster model is the only animal model that closely mirrors the fatal lung disease the virus causes in humans, and infection is almost always deadly: in the unvaccinated control group, by day nine, four of five animals hadn’t survived.
In the vaccinated animals, meanwhile, every animal was protected from disease, and when the study ended, no replicating virus could be found in their tissue. The shots triggered detectable antibodies within 14 days, fast by most vaccine standards.
Reassuringly, the vaccine worked even at fractional doses. The team tested three dose levels: 25, 5 and 1 mcg. Protection held even at the lowest dose, which still generated antibodies in four of five animals.
The ability to protect with so little vaccine matters because in an outbreak, the number of doses that can be squeezed from a limited supply can decide how many people get protected.
Have you read?
Post-exposure protection
The speed of the immune response opens a second possibility: using the vaccine not just to prevent infection, but to stop it in people who have already been exposed.
Andes virus disease has a median incubation of around 18 days in humans. If a vaccine can stimulate the immune system within two weeks, there may be a window to intervene after exposure but before illness sets in.
“If given quickly to high-risk contacts during an outbreak, such as the Andes virus situation on the cruise ship, the vaccines could theoretically jump-start their immune systems fast enough to intercept the virus, stopping it from replicating and preventing them from getting sick or spreading it further,” said Dr Alexander Bukreyev, who heads UTMB’s Laboratory of Viral Pathogenesis and Vaccine Development.
Used this way, a quick shot could double as an emergency tool to box in an outbreak, though the researchers are clear that this remains a hypothesis to be tested, not an established use.
From hamsters to humans
These results, encouraging as they are, come with the caveats that accompany any preclinical study.
The work was done in animals, not people. The team measured the virus only in the liver, so they cannot rule out its presence elsewhere, such as the lungs, though in this model liver levels reliably track with those in the lungs.
The crucial next step is human clinical trials. With backing from the US National Institutes of Health, the UTMB team says it is working to speed the single-dose vaccines toward testing in people.
More from Priya Joi
Recommended for you
