Federal health officials say there is no current need to authorize a bird flu vaccine for use in humans since there is no evidence the disease is spreading from person to person or causing severe illness in people.
Since the spring of 2024, the CDC has confirmed 66 cases of H5 bird flu in humans, most of which have resulted in mild illness. However, the disease is spreading widely among dairy cows and poultry, giving it more opportunities to mutate into something that poses a greater risk to public health.
While the U.S. has a limited number of vaccine candidates in the national stockpile, the shots require FDA authorization before they can be administered to humans. Health officials say the decision to deploy vaccines rests on several criteria, including whether the virus has mutated in ways that render existing antivirals less effective or is causing severe illness.
"When we think about respiratory vaccines, their sweet spot is really in preventing severe disease and death," Nirav Shah, MD, principal deputy director of the CDC, told NBC News in a recent report. "When we look at what is currently unfolding with H5, even in the human cases, thankfully what we've seen thus far is mild disease."
"That is not a guarantee, and that could change, but that is one of the things that we are on the lookout for because the vaccine would be maximally effective against reducing severity of disease," Dr. Shah added.
By the end of the first quarter of 2025, the U.S. will have enough doses to vaccinate 5 million people, if necessary, a spokesperson for the Administration for Strategic Preparedness and Response — the agency that manages the stockpile — told the news outlet.
Three more recent updates:
- In December, the CDC confirmed a patient in Louisiana had been hospitalized with a bird flu infection, marking the nation's first severe case of H5N1 in a person. A genetic analysis of virus samples from the patient showed mutations that may make it easier for it to bind to cell receptors in the upper respiratory tract. The mutations likely developed during the patient's course of infection, indicating they are not widely circulating in wildlife. There is no evidence the patient transmitted the disease to anyone else, the agency said.
- Fragments of the virus are increasingly being detected in wastewater, indicating its spread is much wider than official numbers suggest.
"We've seen detections in a lot more places, and we've seen a lot more frequent detections," in recent months, Amy Lockwood, PhD, told NBC. She leads detection efforts at Verily, the company providing wastewater testing services to the CDC. "We are starting to see it in more and more places where we don't know what the source might be automatically," Ms. Lockwood said. "We are in the throes of a very big numbers game."
- At the end of December, the FDA began collecting samples of raw cow's milk cheese to test for bird flu. The agency plans to collect 300 samples from warehouse and distribution centers nationwide, and conduct PCR testing to analyze genetic material.