Single-Dose Vaccine Demonstrates Protection in Andes Hantavirus Model

In a study published in The Lancet, researchers at The University of Texas Medical Branch (UTMB) report the development of new vaccines that, in animal testing, provided full protection against the deadly Andes hantavirus after a single dose.

Alexander Bukreyev, PhD, head of the Laboratory of Viral Pathogenesis and Vaccine Development at UTMB, said that with backing from the National Institutes of Health, UTMB is working to fast-track these single-dose vaccines into human clinical trials.

The hantavirus drew public attention in May following an outbreak aboard the Dutch cruise ship MV Hondius, which had departed from Argentina. While at sea, the outbreak spread among passengers and crew, infecting 13 people and killing three.

The Andes virus belongs to the hantavirus family but, unlike its viral cousins, it can spread directly from person to person through coughing and close contact. Other hantaviruses are typically spread through contact with infected rodents, making the Andes virus a much more significant public health threat.

The cruise passengers have since returned to their home countries, scattering across 23 nations. Because a person can carry the virus for weeks before showing any symptoms, health agencies face the complex challenge of identifying everyone who was exposed before they unknowingly pass it to others.

Using mRNA technology, Bukreyev and his team, including Ivan V. Kuzmin, PhD, co-designer of the vaccines, had previously created versions that successfully protected animals using a two-dose regimen. Recognizing that a fast-moving international outbreak doesn't allow time for patients to wait weeks between shots, the team retested the vaccines to determine whether a single dose would be effective.

The results exceeded expectations. When testing the vaccines in an animal model that mimics human disease, the scientists found that a single shot provided 100% protection against a lethal dose of the virus. Even when the researchers significantly lowered the dosage to a fraction of the original amount, the results remained definitive.

“Every vaccinated animal remained completely healthy and showed no symptoms or weight loss,” lead author Michelle Meyer, PhD, said. “When we looked at the tissues from the vaccinated animals a month after infection, the virus was entirely gone. The vaccines triggered a powerful immune response, creating protective antibodies in as little as 14 days.”

Because the Andes virus can take a relatively long time to make a human severely ill, these fast-acting vaccines could serve a dual purpose, possibly functioning as an emergency tool for people who have already been exposed.

“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,” Bukreyev said.