No need to provide an avian flu vaccine for humans yet, expert says

Dairy cows gather at a farm on July 5, 2022 in Visalia, California. (Spencer Platt/Getty Images)

An infectious disease expert says the relatively mild cases of avian influenza detected so far among dairy workers don’t warrant making a vaccine available to them, even as they work to contain and prevent spread of the contagious virus among herds.

Dr. Shira Doron, an epidemiologist and chief infection control officer for Tufts Medicine in Boston, said the minor spread of the H5N1 among humans – and no reported instances of human-to-human transmission – makes any widespread administration of a vaccine premature right now.  

“There are also many logistical issues that would be associated with deployment of vaccine to farm workers – language barrier, undocumented status, compliance – so that is not the plan at this time, “ Doron said Friday morning during an Infectious Diseases Society of America teleconference.

H5N1 has circulated globally for decades, she said. Analysis of the strains currently circulating shows them to be poorly suited for transmission between humans and with low pandemic potential, according to Doron. 

Human patients have also responded well to antiviral treatments such as Tamiflu, the doctor said. 

The current avian flu strains have led to two severe cases in humans. One involved a 65-year-old person from Louisiana who contracted the virus from exposure to a combination of a non-commercial backyard flock and wild birds, state health officials said. It was the nation’s first ever fatal human case of avian flu, though the patient was reported to have underlying conditions that worsened after they contracted H5N1. 

The other severe case was a teen in Canada who had to be admitted to a hospital’s intensive care unit. That patient contracted the virus from wild birds, Doron said.    

Dr. Julio Figeroua, LSU Health chief of infectious diseases and a professor at Louisiana State University’s medical school in New Orleans, also took part in the IDSA teleconference. There have been no secondary avian flu cases related to the patient in Louisiana who died, he said. 

“We have people who do hunting, hunting of geese and ducks, and so advisories have been put out to those for proper handling of those particular animals,” Figeroua said. “A lot of backyard flocks that are here and in urban and suburban areas are potentially also potential sources for transmission.”

In addition to 919 dairy herds in 16 states, the highly pathogenic H5N1 strain of bird flu has impacted more than 133 million poultry farms in all 50 states as of Wednesday, according to the U.S. Centers for Disease Control and Prevent. The virus has turned up in two backyard flocks in Louisiana and 49 total across the country, the CDC reported.

Coordination about the various federal and state agencies responding to avian flu outbreaks will be crucial to containing its spread, especially as the incoming Trump administration takes over, Doron and Figueroa said. 

Asked to provide an estimate for when the current H5N1 outbreak might be contained or peter out on its own, Doron said it’s difficult to determine at this point.

“I think it really is going to depend on how long immunity lasts, and it’s too early in the outbreak to know that,” she said. “… If the immunity doesn’t last more than a few months, then we could have ongoing spread indefinitely.”