As memories of the COVID years fade, fears of a coming influenza pandemic are mounting, given recent transmission of H5N1 bird flu among cattle, cats, and a few people. A letter published today in Science from Jesse L. Goodman of Georgetown University Medical Center and colleagues warns us to “prepare now for a potential H5N1 pandemic.”
“Strategies should build on experiences from seasonal influenza, COVID-19, and other outbreaks; use existing infrastructure; and engage those who will implement the programs. Immunization and communications planning must be integrated and engage affected communities, and planning must transcend political divisions,” they write.
But efforts to continue development of mRNA-based bird flu vaccines are facing pushback from the new administration. Vaccine hesitancy may come to be its own epidemic.
Not the Best Time to Threaten Biden-Era Funding of Bird Flu Vaccine Development
On January 17, just days before the end of the Biden administration, the Department of Health and Human Services (HHS) announced $590 million to fund Moderna, the company that pioneered the mRNA COVID vaccine. The last-minute support would speed development of mRNA-based vaccines against “highly pathogenic avian influenza” (HPAI) viral strains, which have already demonstrated safety, tolerability, and immunogenicity in healthy adults.
But scarcely a month later, the new administration announced that it would be “reevaluating” the end-of-the-Biden-era $590 million bird flu vaccine contract with Moderna.
Also Not the Best Time to Cancel FDA Flu Vaccine Meeting
Efforts to seemingly welcome bird flu continue.
Two weeks before the March 13 meeting of the FDA’s Vaccines and Related Biological Products Advisory Committee to discuss the composition of flu vaccines for the 2025-2026 season, the agency emailed the group’s experts that the meeting had been cancelled – no reason given, no hint of rescheduling, according to committee member Paul Offit, professor of pediatrics in the Division of Infectious Diseases at The Children’s Hospital of Philadelphia.
Instead, FDA alone, without independent experts weighing in, would choose the viral strains to be used in next season’s vaccine and inform manufacturers of the recipe. Is jettisoning the advisory committee, a voice to complement that of the government and pharma, really a good idea?
Nor the Best Time to Block Communication
Added to the attack on vaccine development was the several-week “pause” on communications from HHS (which includes CDC, FDA, and NIH) as the new administration took power. A February 3 statement from The Society for Healthcare Epidemiology of America explicitly states the threat from bird flu against the backdrop of communication blocked by non-experts:
“With the order remaining in effect until a new HHS secretary is confirmed, this unpredictable timeline prolongs uncertainty for both healthcare professionals and the public, and endangers the nation by hindering our ability to detect and respond to public health threats, such as avian influenza (H5N1). Public health officials and healthcare professionals are reliant on continual coordination from local to federal levels to know whether avian influenza is becoming more of a threat to humans, and the local response to this threat has been compromised by this, the longest and most comprehensive communication ban to date.”
No, it’s not a great time to fire scientists, snatch grants away from grad students and post-docs, defund research, and slash funding for the indirect costs that keep the lights on and incubators humming. Let’s hope that a federal judge’s overruling of the pause on NIH funding holds.
Flu Rattles Cattle, Birds, and Us
Like a person, a chicken, goose, or turkey with HPAI has a runny nose, coughs and sneezes, lacks energy and appetite, and has difficulty breathing. Eggs become hard or misshapen, as the eyelids, comb, wattles, and shanks swell. Legs turn purple. The head and neck twist painfully, and the bird staggers about and falls. Some simply perish, suddenly, for no apparent reason.
Flu is awful for cows, too. Their noses drip and udders slacken, milk drying up. Farmers shove hoses down their charges’ throats to hydrate them. Birds are more common hosts for influenza viruses, but several flu strains circulating now seem perfectly at home in mammals.
The first sign of H5N1 jumping species was in February 2024, when cows in north Texas stopped lactating. Soon, veterinary researchers identified H5N1 as the culprit. (This DNA Science post explains the H and N nomenclature for flu viruses.) Three veterinarians who cared for the infected cows had bird flu antibodies in their blood.
The USDA reported the cow outbreak in March. The delay raised alarms because the infection was spreading quickly and cows are much more closely related to us than are birds. But inadequate testing and shipping infected cows across state lines quickly spread the virus beyond Texas.
The first case of a person with H5N1 and flu symptoms came in April 2024.
By July, cattle in dairies in Colorado had spread the flu back to birds. When workers culled those flocks, nine of them developed red, infected eyes, aches, and fever. The infectious disease had clearly jumped into people.
Cats get it too, and they tend to have severe symptoms. Infected pet cats have been euthanized due to bird flu. At the St. Louis Zoo a wild wood duck plunged into the lake on the premises, a victim of flu. I hope in its death spiral it didn’t poop on the glorious big cats basking in their outdoor enclosures. And five of my turkey friends on Martha’s Vineyard have succumbed to the virus.
By December, 66 human cases had been reported in 20 states. By the end of February 2025, the number was 70. That’s not a lot of people, but others almost certainly have been infected, but felt no worse than having a cold – or had no symptoms at all.
Importantly, there’s been no evidence that people can spread the virus to each other, as opposed to becoming infected from sneezing turkeys or dripping cows. But mutation enabling person-to-person transmission could happen at any time. And a widened host range could be catastrophic, the possibility likely inspiring the letter in Science.
Vaccinating poultry is one approach to halting a possible pandemic. On February 13, USDA conditionally approved a 2025 H5N1 bird vaccine that is a subcutaneous injection. China, France, Egypt, Mexico and other countries already do this.
Before 2022, bird flu in the US was uncommon enough that culling flocks made sense. But in February of that year, H5N1 mutated into a new variant, or clade (2.3.4.4b), which passes so freely that the situation has gone from epidemic to endemic – in too many areas to cull.
What About People? An mRNA Vaccine is in the Works
Vaccinating birds and cows is all good, but what about us? The National Institute of Allergy and Infectious Diseases is funding development of an mRNA-based vaccine for people against H5N1 bird flu.
Researchers at the Perelman School of Medicine at the University of Pennsylvania reported in May 2024 in Nature Communications on progress in developing an mRNA vaccine against H5N1 bird flu, for humans. Penn is the home of the first mRNA-based COVID vaccine, and one of its developers, Nobelist Drew Weissman, is part of the H5N1 team. Preclinical research shows the vaccine elicits antibody and T cell responses in mice and ferrets, and the antibodies persist beyond a year. If vaxxed animals got sick, symptoms were mild, and all survived; all the unvaxxed controls given dummy vaccine died from the flu.
“The mRNA technology allows us to be much more agile in developing vaccines; we can start creating a mRNA vaccine within hours of sequencing a new viral strain with pandemic potential. During previous influenza pandemics, like the 2009 H1N1 pandemic, vaccines were difficult to manufacture and did not become available until after the initial pandemic waves subsided,” said professor of microbiology Scott Hensley.
“Before 2020, experts thought the influenza virus posed the greatest risk of causing a pandemic, and we had limited options for creating a vaccine if that had happened,” said Weissman in a news release. “COVID-19 showed us the power of mRNA-based vaccines as a tool to protect humans from emerging viruses quickly, and we are better prepared now to respond to a variety of viruses with pandemic potential, including influenza.”
Vaccines have traditionally been incubated in eggs, which takes months, but that’s not necessary with mRNA vaccines. This speeds development. And the mRNA versions worked just as well as those nurtured in eggs for six months.
I hope that H5N1 doesn’t become the next pandemic – we’ve had missed predictions for flu in the past – but if it does, I’m thankful that a vaccine is in the works, using the mRNA approach that saved many of us from COVID.