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Following our recent column on avian (bird) flu, we received two questions. One reader inquired why poultry are not vaccinated to prevent the virus from spreading to humans.
The answer lies in a combination of science, economics, and global trade policies. Unlike vaccines for human diseases like measles or whooping cough, current poultry avian flu vaccines are not very good. They don’t always prevent infection or stop birds from shedding the virus, meaning outbreaks could still occur and spread undetected. Additionally, the constantly evolving nature of the virus means that vaccines might not be effective against new strains, requiring frequent updates and additional costs for poultry producers.
Another hurdle to vaccinating poultry against bird flu is international trade. The U.S. is one of the world’s largest poultry exporters, and many countries — including major buyers like China and the European Union — ban imports from nations that vaccinate against avian flu. This is because vaccinated birds may still carry and spread the virus, making it harder to detect outbreaks through routine testing. A vaccination program could jeopardize billions of dollars in poultry exports.
The U.S. relies on strict biosecurity measures and killing infected flocks (culling) to control outbreaks. This approach aims to quickly eliminate infected flocks before the virus can spread widely. While it results in significant losses, it is considered the most cost-effective method.
With the increasing frequency of avian flu outbreaks and growing concerns about the virus potentially jumping to humans, some experts argue that vaccination should be reconsidered. The U.S. Department of Agriculture is exploring new vaccine options, and some countries, such as France and China, have begun limited poultry vaccination programs. If effective vaccines that do not hinder disease detection become available, the U.S. may consider revising its stance in the future
Given the devastating impact of the Covid-19 pandemic, a second reader asked: Why aren’t we already vaccinating the general population against avian flu?
Currently, infections in humans remain rare and do not spread easily from person to person. The effectiveness of avian flu vaccines in humans is unknown. Most likely, to have a good chance at being effective, the vaccine will need to be a good match for the circulating strain. Flu viruses mutate rapidly, meaning that any vaccine developed now might not be effective against a future strain that gains the ability to spread among humans.
There are experimental vaccines for avian influenza, and some have been stockpiled for emergency use. The stockpiled vaccine would be used to vaccinate those most likely to be exposed, such as poultry workers, healthcare workers, and people in an area of an outbreak. Even if the circulating strain is not a close match, it is hoped that the stockpiled vaccine would provide some protection against serious disease. Given the current political climate, mass-producing and distributing a vaccine for a virus that has not yet become a human pandemic would be challenging.
Vaccine Smarts is written by Sealy Institute for Vaccine Sciences faculty members Drs. Megan Berman, an associate professor of internal medicine, and Richard Rupp, a professor of pediatrics at the University of Texas Medical Branch. For questions about vaccines, email [email protected].
