To stop the devastating global bird-flu outbreak that has killed over 100 million poultry, the U.S. and Europe are embracing a tactic many countries have long resisted: vaccines.
The U.S. and parts of Europe don’t routinely inoculate poultry against bird flu, which emerges every few years and spreads and kills easily, but typically recedes after domestic birds are culled.
Groups representing U.S. poultry companies have historically opposed vaccinating birds over concerns that inoculation could imperil trade. There are also questions about the logistics and cost of administering shots that must be injected into each chick or egg.
But the unprecedented destruction of this outbreak, which has felled 58 million farmed birds in the U.S. and is running into its third year in Europe, has driven governments and businesses to search for options. Animal-health and pharmaceutical companies including
Zoetis Inc.,
Ceva Animal Health, Boehringer Ingelheim and
& Co. have developed vaccines that are in testing.
The U.S. Department of Agriculture’s research service expects results from tests of four vaccines in chickens in late May or early June, said
Erica Spackman,
a bird-flu expert at the agency. Two test vaccines were made by USDA labs and two were developed for past flu outbreaks by Merck and Zoetis. Tests in turkeys and ducks will follow. If effective, any vaccine would need additional approval within the agency before wider use.
France, the world’s top producer of foie gras, this month said it intends to buy 80 million vaccine doses and invited companies to bid for government contracts. Some 21 million birds in the country were culled there as of last summer, and over 200 more outbreaks occurred by the end of the year.
The current dominant strain globally is a version of the H5N1 virus that triggered destruction in Europe in 2021. It was detected in U.S. wild birds in January 2022, and a few weeks later was found in commercial turkey flocks. More than 58 million commercial or backyard birds have died, with detections of the virus in wild birds in 49 states, according to the USDA. In the past few months, South American countries have reported contagious, deadly bird flu for the first time. It has also sickened and killed mammal species including skunks, raccoons, bobcats, bears, seals and mountain lions.
The seasonal virus has shifted to linger for years in wild birds, which pass it to commercial birds. “It’s a biological change in the virus,” said
David Swayne,
a former director of a USDA laboratory that studied the disease. “I don’t think we know genetically what’s changed, but it’s changed such that it’s spread through the wild bird population.”
The persistent circulation in wild birds is “absolutely novel” for the Americas, said
Richard Webby,
an influenza virologist at the Department of Infectious Diseases at St. Jude’s Children’s Research Hospital in Memphis, Tenn. Water birds are likely hosts of the virus, and with the spring migration to the Northern Hemisphere under way, scientists are watching for a surge in cases.
Some countries have endemic versions of the bird-flu virus and regularly vaccinate poultry. But many of those countries don’t have a big trade presence, according to
Leslie Sims,
an avian-flu expert and consultant based in Melbourne, Australia, who has advised governments on animal-disease prevention and control.
“Traditionally, countries have not traded with countries that vaccinate,” said
John Clifford,
a former chief veterinary officer at the USDA and a consultant on trade for the USA Poultry and Egg Export Council. Objections range from concerns that some vaccinated birds will still get sick to the high cost of surveillance required of flocks after a vaccination round, Dr. Clifford said.
The National Chicken Council, which represents companies that produce about 95% of U.S. chickens bred for meat, opposes vaccination because it would threaten $5 billion in annual chicken exports, said spokesman
Tom Super.
France has backed tests of two vaccines in ducks, including an RNA vaccine made by French company Ceva tailored to the current strain of the virus. Another set of French tests involve a vaccine developed by German pharmaceutical and animal-health company Boehringer Ingelheim that contains a synthetic bird-flu virus surface protein, hemagglutinin, that is injected into the birds, said
Jean-Luc Guérin,
chair of avian biosecurity at the National Veterinary School in Toulouse.
Dr. Guérin said results of these tests will be released within a few weeks
The Dutch government has funded research testing vaccines in chickens and is backing field tests and pilots at farms, according to the agricultural ministry. Six million birds were culled in the country because of the outbreak.
In preliminary results reported in March, one research group said that two of four vaccines tested protected chickens against infection by the current variant and prevented the transmission of the disease, according to Sjaak de Wit, professor of veterinary medicine specializing in poultry viruses at Utrecht University in the Netherlands and a member of the team that conducted the tests.
The two effective vaccines, one made by Ceva and the other by Boehringer Ingelheim, both involve a harmless turkey virus that is engineered to include genetic instructions to make hemagglutinin, the bird-flu protein. The engineered virus is injected into the bird, where it multiplies and simultaneously manufactures the protein.
John El-Attrache,
global director at the science and investigation department at Ceva, said South American countries including Paraguay, Ecuador and Uruguay are close to licensing Ceva’s turkey-virus vaccine for bird flu.
It isn’t clear how to stop the virus among wild birds, who continue to harbor and spread infections, said
Daniel Perez,
a virologist at the College of Veterinary Medicine at the University of Georgia.
“We have to think beyond the chickens in the chicken house,” Dr. Perez said.
Write to Nidhi Subbaraman at nidhi.subbaraman@wsj.com
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