The decision brings U.S. poultry farmers a step closer to immunizing their flocks
- 14 Feb 2025
- 3:10 PM ET
- ByJon Cohen
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With egg prices in the United States soaring because of the spread of H5N1 influenza virus among poultry, the U.S. Department of Agriculture (USDA) yesterday conditionally approved a vaccine to protect the birds. President Donald Trump’s administration may therefore soon face a fraught decision on whether to join the ranks of other nations—including China, France, Egypt, and Mexico—that vaccinate poultry against H5N1.
Although many influenza researchers contend that vaccination can help control spread of the deadly virus, the U.S. government has long resisted allowing its use because of politics and trade concerns that many contend are unscientific. The USDA approval may signal a shift in policy linked to the Trump administration’s worries about egg prices. Even with the conditional approval, USDA must still approve its use before farmers can start to administer the vaccine because special regulations apply to H5N1 and other so-called highly pathogenic avian influenza (HPAI) viruses.
The vaccine, made by Zoetis, contains a killed version of an H5N2 variant that the company has designed to work against circulating variants of the H5N1 virus that have decimated poultry flocks and have even jumped to cows and some humans. (The “H” in both variants stands for hemagglutinin, the surface protein of the virus, and antibodies against it are the main mechanism of vaccine-induced protection.) Researchers at the U.S. Centers for Disease Control and Prevention reported yesterday that three cow veterinarians harbored antibodies to the H5N1 virus in dairy cattle. None had symptomatic disease, they noted in the Morbidity and Mortality Weekly Report, suggesting the virus may be more widespread in humans than previously thought.
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Zoetis CEO Kristin Peck announced the approval yesterday on CNBC. “The decision to vaccinate commercial poultry flocks rests solely with national regulatory authorities in consultation with their local poultry sector,” said Zoetis in a statement, which noted it has approval for similar vaccines in other countries. Zoetis also had an earlier version approved in 2016 that was in the National Veterinary Stockpile until 2021, but it was never used.
HPAI strains such as the current H5N1 have for decades been stamped out largely by culling affected flocks and enforcing strict biosecurity measures. But that strategy has failed since the February 2022 emergence in the U.S. of an H5N1 virus that belongs to a lineage known as clade 2.3.4.4b. Many scientists now worry the virus cannot be eradicated from the U.S. poultry flock, which means it has become endemic rather than epidemic.
“The future of H5 in the Americas isn’t entirely clear, but endemicity looks likely,” says Richard Webby, a bird flu investigator at St. Jude Children’s Research Hospital. “Updated and quality H5 vaccines for poultry must be a big part of future responses if this is indeed the case.”
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