Moderna's stock has rallied on hantavirus research that is 'early-stage' in nature

By Jaimy Lee

The biotech company has a pre-clinical program with the U.S. Army and a vaccine center at a Korean university.

An American citizen on Sunday takes photos on his phone after he was evacuated from the MV Hondius in Tenerife, which is part of Spain's Canary Islands.

As the public grows increasingly concerned about the possibility that a hantavirus outbreak on a cruise could spark a new pandemic, Moderna, the biotech company whose quick work developing a COVID-19 vaccine made it a household name, is receiving renewed attention.

The company has been quietly researching hantaviruses for years, and that work is gaining new relevance. Moderna has been studying hantaviruses with the U.S. Army in pre-clinical work and began a partnership in 2024 with the Vaccine Innovation Center at the Korea University College of Medicine to develop mRNA hantavirus vaccines.

Moderna describes both these efforts as "early-stage ," but Moderna's stock (MRNA) has nevertheless rallied amid the renewed interest in the partnerships; its shares rose about 5% in early trading on Monday morning before falling, closing down 2.7%. The stock is up about 11% over the last five days. The company has not shared additional details about either project.

Read: There are no hantavirus treatments. The deadly cruise-ship outbreak is a 'wake-up call' to develop some.

Analysts say the stock rally is driven by retail investors who may not fully understand that a hantavirus vaccine wouldn't be profitable.

"Hantavirus is a low-incidence, structurally small market," Evercore ISI analyst Cory Kasimov told investors last week. "We view any potential outsized moves as sentiment-driven, not fundamental. At most, it reinforces Moderna's mRNA platform agility, something already well understood post-COVID."

The hantavirus outbreak captivating the public began on the MV Hondius, an expedition-style cruise ship operated by Oceanwide Expeditions, a privately held Dutch company. Health officials believe a couple contracted the Andes virus - a rare type of hantavirus - while traveling in remote areas of Argentina, Chile and Uruguay before the cruise, which departed from Ushuaia, Argentina. The Andes virus is endemic to Argentina and Chile.

Three people, including the couple, have died, and eight more are ill. All were on board the ship.

At least one American who was on the ship and returned to the U.S. has tested positive for the Andes virus, according to the Department of Health and Human Services. Another has mild symptoms and is waiting for the results of a PCR test. Over the weekend, those patients and about a dozen other Americans from the ship were transported by the State Department from Spain's Canary Islands to a special pathogen treatment center at the University of Nebraska Medical Center in Omaha.

The Andes virus is unique among hantaviruses for three reasons: It can be spread between people in close contact; the fatality rate is as high as 50%; and the incubation period can be as long as 42 days.

Most hantavirus infections occur when people are exposed to contaminated droppings, urine or saliva of infected rodents. There were only about 230 hantavirus infections in the Americas last year, according to the Pan American Health Organization, and none have ever been recorded on a cruise ship. That's one reason why this outbreak is an outlier.

Like Moderna, several small biotechs have said they are working on hantavirus vaccines or treatments. Traws Pharma said it's developing a therapy to treat infections of another type of hantavirus, the Hantaan virus. Its stock (TRAW) was up about 7% on Monday before tumbling to a 7% decline, but it's still up 34% over the past five days. One of the company's leaders is Robert Redfield, the head of the CDC during the first Trump administration.

Gilead Sciences (GILD), another major player in the pandemic response that brought to market the first novel treatment for COVID, told Cantor Fitzgerald analysts that it considered working on therapies for hantavirus infections but "participation would be unlikely at this time."

-Jaimy Lee

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05-11-26 1641ET