Publisher Health

WASHINGTON — The Biden administration, keeping a watchful eye on an outbreak of avian influenza that has led to the deaths of tens of millions of chickens and is driving up the cost of eggs — not to mention raising the frightening specter of a human pandemic — is contemplating a mass vaccination campaign for poultry, according to White House officials.

The bird flu outbreak, which began early last year, is the biggest in the nation’s history, affecting more than 58 million farmed birds in 47 states, as well as birds in the wild. It has already spilled over into mammals, such as mink, foxes, raccoons and bears, raising fears that the virus that causes it, known as H5N1, could mutate and start spreading more easily among people.

Experts at the Centers for Disease Control and Prevention, whose focus is human health, say the risk of a pandemic is low. As a precaution, the agency has sent drug manufacturers flu virus samples that could form the basis of vaccines for people. The C.D.C. is also exploring whether commercial test manufacturers would be willing to develop tests for H5N1, similar to those used for the coronavirus.

Bird flu infections in humans are rare, and transmission of bird flu between humans is extremely rare. Worldwide, there have been nine H5N1 cases reported in people since the beginning of last year, according to the World Health Organization. In Cambodia, an 11-year-old girl recently died from H5N1 and her father was also infected with it, though the virus was a different version than the one currently circulating in birds in the United States.

Cases typically involve people exposed to poultry. In the United States, the C.D.C., in partnership with state and local public health departments, is monitoring people who are exposed to H5N1. As of last week, 6,315 people had been monitored; 163 reported symptoms; and one tested positive, according to Dr. Tim Uyeki, the chief medical officer of the C.D.C.’s influenza division.

At the same time, officials at the federal Agriculture Department, which is responsible for the health of farm animals, say they have begun testing potential poultry vaccines and initiated discussions with industry leaders about a large-scale bird flu vaccination program for poultry, which would be a first for the United States.

Farm birds are already vaccinated against infectious poultry diseases, such as fowlpox. But an avian influenza vaccination program would be a complex undertaking, and poultry trade associations are divided over the idea, in part because it might spawn trade restrictions that could destroy the $6 billion poultry export industry. Dr. Carol Cardona, an expert on avian health at the University of Minnesota, said that the fear of trade bans was a huge barrier to the mass vaccination of poultry.

“This is the undeclared war — trade,” Dr. Cardona said.

Avian influenza experts, however, say they believe the Biden administration should move ahead with a vaccination campaign, in part to reduce the risk of a human pandemic. In interviews, several called for the administration to act quickly.

“My own opinion is under the present circumstances, we should be vaccinating the poultry population of the United States against H5N1 — absolutely,” said Robert G. Webster, an expert in avian influenza at St. Jude Children’s Research Hospital in Memphis. Such a campaign could “prevent the inevitable transmission to humans,” he said.

For President Biden, there are also political considerations at work. Egg prices, which soared in 2022, were 70 percent higher in January than they were a year earlier. Those high prices have given Republicans another opportunity to attack Mr. Biden over inflation just as he is preparing to run for re-election in 2024.

Experts say egg prices could continue rising through the spring, driven in part by Easter season demand but also by supply shortages linked to the bird flu outbreak. And the outbreak may worsen in the months ahead as wild birds begin their spring migrations, bringing the virus with them.

White House officials, speaking on the condition of anonymity to describe internal deliberations, said they were watching the price fluctuations closely. If a vaccination campaign could provide economic relief for households, Mr. Biden would certainly be interested in such an undertaking, one official said.

Experts have long worried that a human-adapted version of bird flu could set off a global pandemic. For that reason, the United States and the world need to be doing more to prepare, said James Krellenstein, an adviser to Global Health Strategies, an international consulting firm.

Mr. Krellenstein and Garrett Wilkinson, a health policy expert at the nonprofit Partners in Health, examined the world’s readiness for an H5N1 pandemic and identified several “important gaps,” according to a report they shared with The New York Times. With a two-dose regimen, the United States could need at least 650 million doses of H5N1 vaccine for use in humans, and the report said it was unclear how the country could reach that figure with its current manufacturing capacity.

“While it is extremely important that serious efforts are taken to bring the outbreak in domestic and wild birds under control, the reality of the situation is serious enough that we must be taking more steps to prepare for a possible human outbreak of this virus,” Mr. Krellenstein said in an interview, adding, “We should be viewing this as a live-action fire drill.”

Before Covid-19, many experts predicted that the next pandemic would be caused by influenza. In 2020, the federal Department of Health and Human Services published a 10-year strategy for updating influenza vaccine production; one of the White House officials said the Biden administration was reviewing the document in light of the current outbreak in birds.

One step toward pandemic preparedness, many experts agree, would be a poultry vaccination campaign.

“Just having the virus be less widespread would reduce the exposures to humans,” said Anice C. Lowen, an influenza virologist at Emory University, adding that a vaccination effort “would also reduce the potential for viral evolution” that might enable the virus to spread efficiently from person to person.

Currently, federal regulators have not authorized the vaccination of poultry against highly infectious bird flu strains like H5N1, said Mike Stepien, a spokesman for the Agriculture Department. While there are several licensed vaccines, it is unclear whether any of them are effective against the current strain, he said.

Scientists at the department have been working to develop vaccine candidates in-house, said Erica Spackman, a research microbiologist at the agency’s Agricultural Research Service, who is one of the scientists leading the testing of the poultry vaccines. Dr. Spackman and her colleagues are aiming to test multiple potential vaccines — including those already licensed and the new vaccine candidates — in chickens, turkeys and domestic ducks, she said.

If the existing vaccines prove effective, they could potentially be deployed more quickly than new vaccines. Typically, the approval process for animal vaccines can take up to three years, though Mr. Stepien said that time frame could be shortened in an emergency.

Dr. Spackman estimated that she and her colleagues would probably not have their first set of results ready to share until May. “And then there’s always the issue on the production side of how quickly the company could actually produce and supply the vaccine,” she added.

Beyond the science, there are economic considerations. The United States is the world’s biggest exporter of poultry products, and its trading partners want assurances that they are not importing meat from infected birds. Vaccination could make it more difficult to prove that birds had not been infected.

Broilers — the industry term for chickens raised for their meat — account for the vast bulk of exported poultry, said Amy Hagerman, an agricultural economist at Oklahoma State University. So it is perhaps not surprising that the National Chicken Council, which represents the broiler industry, opposes vaccination.

“Although initially appealing as a simple solution to a widespread and troublesome problem, vaccination is neither a solution nor simple,” said Tom Super, the council’s senior vice president for communications.

He said that the broiler industry exported 18 percent of its meat and that losing the ability to export chicken would cost it “billions and billions of dollars.”

But the turkey sector, which has been hit hard by the virus and exports just 9 percent of its meat, is open to vaccination. “We recognize that unilateral vaccination would have a severe impact on exports,” said Joel Brandenberger, the president of the National Turkey Federation. “At the same time, we have urged and continue to urge the federal government to move as rapidly as possible to try to develop new agreements” with trading partners.

Avian influenza is typically carried by waterfowl and shorebirds, which pass the virus to poultry through their feces or respiratory secretions. During past outbreaks, officials have stamped out the virus by tightening biosecurity measures, quarantining affected farms and culling infected flocks. But with the virus now unusually widespread in wild birds, those steps have failed to contain the spread.

A handful of countries in which avian influenza is endemic, including China, Egypt and Vietnam, already routinely vaccinate poultry against it. The vaccines are typically injected into individual birds and require more than one dose, said Dr. Leslie Sims, an international veterinary consultant on the prevention and control of zoonotic diseases who is based in Australia.

Although the cost varies, it can be as low as a few cents per dose, he added.

Still, even vaccine proponents acknowledge that a mass vaccination campaign would not be a quick endeavor. The United States produces more than nine billion chickens per year for meat alone. It might take a large egg-laying facility, which could contain five million birds, two years to vaccinate enough birds to achieve high levels of population immunity, Dr. Cardona said.

Some critics have previously raised concerns that vaccination could reduce the severity of disease in birds without stopping transmission, which might allow the virus to spread through flocks undetected while also spurring the emergence of new, immune-evasive variants. But Richard J. Webby, a bird flu expert at St. Jude Children’s Research Hospital, said there was “not a lot of evidence for that, at least in a quality vaccination program.”

Whatever path the United States takes, Dr. Webby said, the virus is likely to become endemic in wild birds in America.

“This thing,” he said, “is here to stay.”