In the face of serious concerns over the spreading bird flu virus in US agriculture, the US Centers for Disease Control and Prevention (CDC) is pushing a major flu vaccination campaign among farm workers in a bid to prevent healthcare strain and combat potential mutations from the highly pathogenic bird virus.
Part of the campaign will seek to combat disinformation about vaccines, which has hampered previous efforts.
There are approximately 200,000 livestock workers in the United States, although the tally likely leaves out unofficial workers. It’s not clear what vaccination rates look like in the livestock industry. On average, only 47% of Americans get the flu shot each year.
Nirav Shah, principal deputy director of the CDC, said he was optimistic the vaccine campaign will be successful.
“Many agricultural and livestock workers come from countries where vaccination is very commonplace, well-accepted and rates are very high,” he said. If farm workers do have low rates of vaccination, “the reason is access, not reticence”, he added.
The new $5m campaign will bring seasonal flu shots to farm workers and another $5m will go toward strengthening healthcare for them, including improved access to testing, treatment and personal protective equipment.
The campaign will distribute the seasonal flu shot, but not an H5N1-specific vaccine for bird flu, among communities that may have limited access to health care.
The US ordered 4.8m doses of an H5N1 vaccine in May, and vials are now coming off the production line. The US has also entered into an agreement with Moderna to produce an mRNA vaccine for bird flu, expected to begin trials in 2025.
The new vaccines have not yet been approved by the Food and Drug Administration (FDA), though there are options to use medications before clinical trials are complete through the FDA’s expanded access program for people at high risk of severe illness or death.
Officials maintain the bird flu vaccines are not recommended for anyone at this time, while acknowledging the higher risk for farm workers compared to the general public.
For farm workers and close contacts of people who test positive, the CDC is instead recommending flu antivirals: preapproved drugs that may work better to block transmission than flu vaccines typically do. Antivirals may be used before or after a person is exposed to a virus.
The seasonal flu vaccine is being offered to protect the health of farm workers as well as the functionality of health systems, said Shah.
“Healthcare systems in rural areas can easily be overwhelmed – that’s true even in regular flu season,” he said. “Vaccination against seasonal flu helps reduce the strain on hospitals.”
In the 2022, the flu shot prevented 6m illnesses, 65,000 hospitalizations and 3,700 deaths, according to the CDC.
Officials also hope the seasonal flu vaccine will reduce the chance of co-infection – when someone gets sick with multiple strains of the flu at the same time. While the flu shot doesn’t prevent all infections, it can lower the risks.
The seasonal flu shot could thus help prevent reassortment, where a worker might get bird flu and human flu at the same time and mix them to make an even worse variant.
“In theory, reassortment could lead to a new influenza virus that could pose a significant public health concern: a virus that has the transmissibility of seasonal influenza and the severity of H5N1,” Shah said.
The new campaign will focus on increasing access, but strategies will likely differ depending on the state, Shah said. States may work with local health care providers and county health departments, they could go directly to farms and they could set up clinics and vaccination tents at social gatherings, churches, fairs and community centers.
There are a few reasons US officials don’t recommend the bird flu vaccine for people yet, Shah said. So far, no one in the US has been hospitalized or died from H5N1, despite a global 50% mortality rate from this strain. The main symptom has been conjunctivitis, or pink eye, though some patients have developed more typical flu symptoms like coughing and sore throat.
The virus also isn’t showing mutations to become more transmissible among people, and there isn’t evidence that the virus is spreading from person to person, though testing remains very limited.
Health officials seem to see the US outbreak as a series of anomalies: no one has gotten very sick yet; they believe they can arrest the spread in livestock. A recent spate of cases among poultry workers in Colorado, where nine people tested positive, may be attributed to unusually high heat, making personal protective gear less effective, they say.
They weigh these concerns, which they see as relatively unusual, against longer-term issues like the spread of misinformation that may result in vaccine hesitancy.
“Anything that happens following vaccination, whether caused by the vaccine or not, would and could be attributed to the vaccine, at least in the minds of the public,” Shah said. “And that could destroy confidence in that vaccine. It could destroy confidence in all vaccines for a number of years.”
In 1976, for example, an outbreak of a pandemic-potential swine flu led to a widespread vaccination campaign that was soon engulfed in misinformation. An extremely rare side effect known as Guillain-Barré syndrome emerged – but that’s not what engendered skepticism, Shah says.
Several people had heart attacks after getting their vaccines in the same location. An investigation later ruled out a connection to the vaccine – “people have heart attacks,” Shah said – but the association was already set among the public.
Similar anti-vaccine sentiment exploded from the fringes into the mainstream during the Covid pandemic. Some misinformation campaigns falsely attributed illness and death to vaccines.
“What’s different here is that this would be a new vaccine, and with anything new – Covid vaccines, a new drug, a new surgical procedure – all eyes are on that,” Shah said. “Do the benefits outweigh the risks?”
It’s a question health officials will weigh as the bird flu outbreak continues.
In the meantime, farm workers and others in close contact with animals continue to face elevated risks of bird flu.
The CDC recently changed its procedures to make flu antivirals like Tamiflu easier to access.
“Tamiflu is a very viable option before we get to this point of vaccination, and we are embracing it,” Shah said. “On any kind of farm setting where any worker has been exposed, we have recommended it.”
Antivirals help reduce severity of illness, and they can also keep viruses from being transmitted by suppressing the amount of virus a person has in their body.
Workers could also take the medicine before they’re exposed, in order to prevent infection entirely.
“We’re discussing that, too,” Shah said. “It raises some tough questions, though. How long should they be taking it? What about the side effects?”
But short-term use of the medication could be especially helpful for workers who are culling infected poultry and milking infected cows, particularly since the high-heat conditions implicated in the Colorado outbreak are expected to continue in many places.
