As the H5N1 avian flu continues to spread among dairy cows in the United States, nearly 5 million doses of flu vaccine are now being prepared for possible use in humans.

Since the outbreak in livestock began this spring, bird flu has been confirmed in three humans who worked on dairy farms in Texas and Michigan and health experts are concerned the virus could mutate to the point where it could spread easily among humans.

In response, vaccine maker CSL Seqirus announced last week that it has been tasked with making the additional doses of flu vaccine at its North Carolina plant.

“It utilizes a highly scalable method of production and is currently positioned to deliver up to 150 million influenza vaccine doses to support an influenza pandemic response within six months of a pandemic declaration,” the company noted in a news release.

“The CDC [U.S. Centers for Disease Control and Prevention] maintains the risk to public health as low. We are closely monitoring the situation because we are acutely aware of the threat that influenza virus strains like H5N1 can pose and take seriously our role in preparedness efforts alongside our government and public health partners,” Marc Lacey, global executive director for pandemic at CSL Seqirus, said in the news release. “This agreement… will help support the U.S. government’s ability to respond swiftly in the event that the current avian flu situation changes.”

The new vaccine doses combine an antigen that targets the H5 portion of the H5N1 virus with an ingredient designed to boost the immune response triggered by the vaccine.

While the production of these new flu vaccine doses is set to be completed “later this summer,” they may not be ready for use right away.

The U.S. Food and Drug Administration has previously approved other vaccines for potential H5N1 pandemics, including a vaccine by Seqirus, but it isn’t certain how soon the FDA might clear use of the new shots. 

“If it is determined that the U.S. population needs to be vaccinated to prevent H5N1 influenza, then the FDA will use its regulatory pathways to take the appropriate steps to ensure vaccines are available in the timeliest manner possible,” an FDA spokesperson told CBS News.

It is unclear who would be prioritized for the first shots if they are eventually rolled out for the public, CBS News reported.

A panel of the CDC’s outside vaccine advisers is set to meet June 24 to discuss H5N1 alongside its routine votes on seasonal flu vaccines. 

While the CDC says the risk to the general public remains low, the agency has warned that workers on dairy farms and in production facilities are at higher risk of infection and it has urged the industry to take safety precautions.

The latest human case of bird flu in Michigan involved respiratory symptoms for the first time, officials announced Thursday, which could make it easier for the virus to spread from person to person. The two previous patients only experienced eye symptoms.

“Simply put, someone who’s coughing may be more likely to transmit the virus than someone who has an eye infection like conjunctivitis,” the CDC’s Nirav Shah said Thursday, CBS News reported.

The CDC is now investigating whether the strain that infected the latest Michigan patient might have developed key mutations that could raise its risk of spread among humans, CBS News reported.

“The mere fact that this individual displayed some respiratory symptoms, again we should be alert, but in and of itself is not a cause to change course or suggest that we’re at an inflection point,” Shah told reporters.

More information

The U.S. Centers for Disease Control and Prevention has more on bird flu.

SOURCE: CSL Sequiris, news release, May 30, 2024; CBS News

Source: HealthDay