Flu vaccine will reduce bird flu risk for US farm workers, CDC deputy director says
Due to serious concerns about the spread of the bird flu virus in U.S. agriculture, the U.S. Centers for Disease Control and Prevention (CDC) is promoting a large-scale flu vaccination campaign among farmworkers to prevent health care illnesses and to combat possible mutations of the highly pathogenic bird virus.
Part of the campaign is aimed at combating vaccine misinformation that has hampered previous efforts.
There are about 200,000 livestock farmers in the United States, although the count likely excludes unofficial workers. It is unclear what vaccination rates are in the livestock industry. On average, only 47 percent of Americans get the flu shot each year.
Nirav Shah, deputy director of the CDC, said he is optimistic the vaccination campaign will be successful.
“A lot of farm and livestock workers come from countries where vaccination is very common, well accepted and vaccination rates are very high,” he said. If farm workers do have low vaccination rates, “the reason is access, not reluctance,” he added.
The new $5 million campaign aims to vaccinate farmworkers against seasonal flu, and another $5 million is aimed at improving health care for them, including increased access to testing, treatment and personal protective equipment.
The campaign will distribute the seasonal influenza vaccination, but not the H5N1-specific avian influenza vaccine, in communities that may have limited access to health care.
The U.S. ordered 4.8 million doses of an H5N1 vaccine in May, and vials are now rolling off the production line. The U.S. has also entered into a deal with Moderna to produce an mRNA vaccine for bird flu, with testing expected to begin in 2025.
The new vaccines have not yet been approved by the Food and Drug Administration (FDA). However, there are options to use the drugs before clinical trials are complete, through the FDA’s expanded access program for people at high risk of serious illness or death.
Officials say the bird flu vaccine is not currently recommended for anyone, but acknowledge that farm workers are at higher risk than the rest of the population.
For farmworkers and close contacts of people who test positive, the CDC instead recommends flu antivirals, pre-approved medications that may work better at blocking transmission than flu vaccines typically do. Antivirals can 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 and the functionality of health care systems, Shah said.
“Health care systems in rural areas can easily become overwhelmed – even during the regular flu season,” he said. “Vaccination against seasonal flu helps to reduce the pressure on hospitals.”
According to the CDC, the flu shot prevented 6 million cases of illness, 65,000 hospitalizations, and 3,700 deaths in 2022.
Officials also hope the seasonal flu vaccine will reduce the risk of co-infection — when someone gets sick with multiple strains of the flu at once. While the flu vaccine doesn’t prevent all infections, it can reduce the risk.
The seasonal flu shot could therefore help prevent reassortment, where an employee gets bird flu and human flu at the same time and mixes them into an even worse variant.
“In theory, reassortment could lead to a new influenza virus that could pose a significant public health problem: a virus as contagious as seasonal influenza and as severe as H5N1,” Shah said.
The new campaign will focus on expanding access, but strategies will likely vary by state, Shah said. States can partner with local health care providers and county health departments, they can go directly to farms, and they can set up clinics and vaccination tents at social gatherings, churches, fairs and community centers.
There are a few reasons U.S. officials aren’t yet recommending the bird flu vaccine for people, Shah said. So far, no one has been hospitalized or died from H5N1 in the U.S., despite a 50 percent global mortality rate from the strain. The main symptom was conjunctivitis, or pink eye, though some patients developed more typical flu symptoms, such as coughing and a sore throat.
There are also no mutations that make the virus more contagious between people. There is also no evidence that the virus spreads from person to person. However, few tests have been done.
Health officials appear to view the U.S. outbreak as a series of anomalies: No one has gotten seriously sick yet; they believe they can stop the spread among livestock. A recent rash of cases among poultry workers in Colorado, where nine people tested positive, can be attributed to unusually high temperatures, which make personal protective equipment less effective, they say.
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They weigh these concerns, which they see as relatively uncommon, against longer-term problems such as the spread of misinformation that could lead to vaccine hesitancy.
“Anything that happens after vaccination, whether it’s caused by the vaccine or not, could and should 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 quickly overrun with misinformation. An extremely rare side effect known as Guillain-Barré syndrome emerged — but that wasn’t what prompted skepticism, Shah says.
Several people had heart attacks after getting their vaccine at the same location. An investigation later ruled out a link to the vaccine — “people are having heart attacks,” Shah said — but the link had already been established among the public.
Similar anti-vaccine sentiment exploded from the fringes into the mainstream during the Covid pandemic, with some disinformation campaigns falsely blaming illness and death on 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 be asking themselves as the bird flu outbreak continues.
Meanwhile, farm workers and others who have close contact with animals remain at increased risk of bird flu.
The CDC recently changed its procedures to make flu antiviral drugs, such as Tamiflu, more readily available.
“Tamiflu is a very viable option before we get to this point of vaccination, and we embrace it,” Shah said. “On every farm where a worker has been exposed, we have recommended it.”
Antiviral drugs help reduce the severity of an illness and can also prevent viruses from being transmitted by suppressing the amount of virus in a person’s body.
Workers can also take the drug before exposure to completely prevent infection.
“We’re discussing that as well,” Shah said. “It does raise some tough questions. How long do they have to take it? And what are the side effects?”
However, short-term use of the drug may be most helpful for workers who cull infected poultry and milk infected cows, especially since the extreme heat that accompanied the Colorado outbreak is expected to persist in many places.