The New York Times: Scientists Begin Testing Bird Flu Vaccine in Seals

Published by The New York Times: September 9, 2025

Wildlife veterinarians have begun testing bird flu vaccines in marine mammals, which have suffered enormous losses in the ongoing global outbreak. The first trial, which began in July, is tiny, enrolling just six northern elephant seals that were already being rehabilitated at the Marine Mammal Center in Sausalito, Calif.

But if the results are promising, the researchers hope to quickly begin vaccinating wild Hawaiian monk seals, an endangered species that they fear could be wiped out by the virus.

Just 1,600 of the seals remain in the wild, living primarily around a remote chain of Hawaiian islands. Over the coming weeks, scores of migrating birds will arrive in the Aloha State, potentially bringing the virus with them.

“There is some urgency, this virus is on the move.”

“There is some urgency,” said Dr. Sophie Whoriskey, the associate director of Hawai’i Conservation Medicine at the Marine Mammal Center, which is leading the trial in consultation with the National Oceanic and Atmospheric Administration. “This virus is on the move.”

A decision about whether to vaccinate monk seals will be made in consultation with the agency, Dr. Whoriskey said.

Rachel Hager, a spokeswoman for NOAA, referred questions about the trial to the Marine Mammal Center. “We will take the center’s results into consideration as we work to ensure the survival of our nation’s at-risk marine species,” she said in an emailed statement.

Over the last few years, a new version of the bird flu virus known as H5N1 has spread around the world, decimating wild birds and farmed poultry, jumping into dairy cows and infecting dozens of U.S. farmworkers.

It’s also taken a toll on marine mammals. In late 2023, the virus tore through Valdés Peninsula in Argentina, killing an estimated 17,400 southern elephant seal pups.

It was an unfathomable loss, of a scale that the tiny Hawaiian monk seal population would be unlikely to survive.

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