Hoping for a vaccine

Highly pathogenic avian influenza (HPAI) isn’t the primary news story today, but the virus is here to stay. Veterinarian Eric Gingerich, technical services specialist, Diamond V/Cargill, promotes biosecurity, but he’s hoping for vaccine approval. Gingerich recently provided an HPAI review and an update on vaccine status.

HPAI is a deadly virus to most avian species, Gingerich said. “There are also a lot of mammals affected by it. We’re all hoping this doesn’t mutate and become a pandemic in humans – that’s a possibility researchers have brought up.”

Clinical signs of HPAI in birds include depression, along with swollen heads and wattles because it affects the circulatory system. Other signs include drop in egg production, severe coughing, nasal exudate and acute death.

The HPAI virus is shed in both respiratory and fecal material. Transmission to domestic poultry begins when wild birds defecate over and around poultry houses. The virus is then tracked in or blown in with wind or dust. HPAI hitches a ride on feed trucks, employee clothing and on inanimate objects such as feed bags, buckets and tools. It’s also spread during manure removal.

HPAI can be present in dry material such as feathers and dust, and in plant materials such as cornstalks that blow around houses.

Many avian and mammal species may be involved with infection and virus mutation. Gingerich listed numerous domestic species susceptible to avian influenza viruses including humans, pigs, horses, cats and dogs. Wildlife affected include foxes, rats, large cats, squirrels, bears and bats. Wild bird species such as ducks, upland game birds, eagles and geese are frequent HPAI spreaders. Not all infected species succumb to the virus but can transmit it to susceptible species.

“In 2024 we had the jump from wild birds to dairy cattle,” Gingerich said. “There was significant transmission from dairy herds to egg layers in several states, and 80% of HPAI outbreaks in poultry were dairy related.”

Losses to HPAI are highest in layer flocks, mostly due to traffic in and out of layer complexes. Young birds are more resistant to HPAI infection than older birds, which is why most broilers and pullets aren’t affected. Turkeys seem to be more susceptible than chickens.

The HPAI virus survives well in cold, wet and foggy conditions. Sunlight or UV light help knock back the virus.

The circulation of HPAI, both worldwide and in the U.S., has been primarily through migratory birds. HPAI often starts when wild birds deposit feces close to vents at the end of a poultry house where people haven’t entered. The virus is present at the top and moves downward through vents.

Total losses in 2025 included about 54 million birds, primarily layers. North Carolina, Pennsylvania, Maryland, Delaware and Virginia were among the top states affected. Layer flocks make up the majority of losses due to egg trucks, feed trucks, employee vehicles, manure removal and service people moving on and off the property.

Present HPAI control involves depopulation to eliminate infected birds as a source of virus. In some cases, surveillance programs detect the presence of virus before clinical signs are evident or mortality begins. Testing for HPAI involves a tracheal swab sample and lab testing.

Backyard flocks have the same disease pattern as commercial flocks, and HPAI-positive birds are found in live bird markets. Although there’s no single answer to the problem, Gingerich said a vaccine would positively impact the layer industry.

“Vaccination is done in some countries – mainly countries that don’t export,” Gingerich said. “It’s done to maintain a supply of eggs and poultry meat for their populations. In the U.S. we can afford to [depopulate] where other countries cannot.”

There are eight USDA-licensed vaccines for poultry, including two that include HPAI. However, licensing doesn’t mean the vaccines can be used.

“We need approval from USDA before we can use [vaccines],” Gingerich said. “The most important are a live Marek’s disease vaccine that has the avian influenza antigen and an H5N2 killed vaccine that would be useful for layers and turkeys.”

Gingerich described the requirement proposal for HPAI vaccine: Rather than a countrywide program, the vaccine would be compartmentalized and only used regionally, primarily in high egg layer regions and possibly in strong turkey production areas. Vaccine requirements also involve continued pressure for improved biosecurity and a robust surveillance program for HPAI presence.

The Proposed U.S. Poultry & Egg Industry Vaccination Plan for HPAI for layers was published in April 2025. It states that the initial vaccine with the H5 antigen would be administered in ovo (in the egg) or on day one. At seven to 15 weeks, birds would receive an inactivated H5 vaccine booster.

“This inactivated vaccine would boost birds’ immunity so they have improved resistance to infection and reduced shed rate,” Gingerich said. “We would have reduced morbidity and mortality. With reduced shed of the virus into the environment, the virus would likely not spread as fast or as widely to neighboring houses or within the house. Improved resistance could mean no infection at all.”

One of the problems with any vaccine for viral disease is mutation. The HPAI virus mutates constantly, and China frequently updates their vaccines due to mutation. Companies producing the HPAI vaccine would have to be capable of adapting to mutations.

Gingerich pointed out that mRNA vaccines are more easily changed to adjust to current strains compared to killed vaccines that take longer to update.

The reluctance for full approval of vaccines is due to trade restrictions. Many countries will not allow trade of meat or eggs from U.S. vaccinated birds.

“It’s important to maintain trade,” Gingerich said. “The broiler industry is worth $5 billion each year, and turkey and eggs also contribute to strong trade for a total of about $6 billion. The value of our exports is a lot higher than the $450 million the U.S. government is paying in indemnity.”

Gingerich said HPAI has caused great economic loss and market disruption in the U.S., and believes vaccination would aid greatly in reducing losses, especially in the layer industry.

“Trade restrictions have prevented the use of vaccination to date,” said Gingerich. “To implement a vaccination program, we need a great deal of negotiation between trade partners to use a compartmentalized vaccination scheme that would allow normal trade for the broiler industry.”

by Sally Colby