Even news about a new flu pandemic it's enough to make scientists crack their eggs.
They worried about them in 2005 and 2009, and they're worrying about it now. That's because millions of fertilized chicken eggs are still the main ingredient in making vaccines that will hopefully protect people against the outbreak of a new strain of flu.
“It's almost comical to use a technology from the 1940s for a 21st century pandemic,” said Rick Bright, who led the Health and Human Services Department's Advanced Biomedical Research and Development Authority during the Trump administration.
It is not so funny, he said, when the currently stored formulation against him H5N1 bird flu virus requires two injections and 90 micrograms of antigen, but provides average immunity. “For the United States alone, it would take chickens to lay 900,000 eggs every day for nine months,” Bright said.
And that only if the chickens do not get infected.
The spread of an avian flu virus has flocks of decimated birds (and killed barn cats i other mammals). Livestock in at least nine states and at least two people in the United States have been infected, enough to return public health attention to the potential for a global pandemic.
So far, the only one confirmed human cases of infection were dairy workers in Texas and Michigan, both of whom suffered pink eye and recovered quickly. However, the spread of the virus to multiple species over a wide geographic area poses the threat that further mutations could create a virus that spreads from human to human through airborne transmission, causing respiratory infections.
If they do, prevention starts with the egg.
To make the raw material for a flu vaccine, the virus is grown in millions of fertilized eggs. Sometimes it doesn't grow well, or it mutates to the point that the vaccine product stimulates antibodies that don't neutralize the virus, or the wild virus mutates to the point that the vaccine doesn't work against it. And there's always the terrifying prospect that wild birds could carry the virus into the chicken coops needed for vaccine production.
“Once those roosters and hens come down, you don't have any vaccine,” Bright said.
Since 2009, when an H1N1 swine flu pandemic swept the world before vaccine production could get underway, researchers and governments have been looking for alternatives. Billions of dollars have been invested in vaccines produced in mammalian and insect cell lines that do not carry the same risks as egg-based injections.
“Everybody knows that cell-based vaccines are better, more immunogenic and have better production,” said Amesh Adalja, an infectious disease specialist at the Johns Hopkins University Center for Health Security. “But they are handicapped by the influence of egg-based manufacturing.”
The companies that make the cell-based flu vaccines, CSL Seqirus and Sanofi, also have billions invested in egg-based production lines that they don't want to replace. And it's hard to blame them, said Nicole Lurie, assistant assistant secretary for preparedness and response at HHS under President Barack Obama, who is now executive director of CEPI, the global nonprofit fighting the epidemic .
“Most vaccine companies that responded to an epidemic (Ebola, Zika, COVID) ended up losing a lot of money,” Lurie said.
The exceptions were mRNA vaccines created for COVID, though even Pfizer and Moderna have had to destroy hundreds of millions of doses of unwanted vaccine as public interest waned.
Pfizer and Moderna are testing seasonal flu vaccines made with mRNAand the government is soliciting bids for mRNA vaccines against pandemic influenza, said David Boucher, director of infectious disease preparedness for HHS's Strategic Response and Preparedness Administration.
Bright, whose agency invested $1 billion in a cell-based flu vaccine factory in Holly Springs, North Carolina, said there is “no way to fight a pandemic H5N1 with an egg-based vaccine.” But for now, there is little choice.
BARDA has stockpiled hundreds of thousands of doses of a vaccine for the H5N1 strain that stimulates the creation of antibodies that appear to neutralize the virus currently circulating. It could produce millions more doses of the vaccine in a few weeks and up to 100 million doses in five months, Boucher told KFF Health News.
But the vaccines currently in the national stockpile are not a perfect match for the strain in question. Even with two vaccines that contained six times more vaccine substance than typical flu shots, the stored vaccines were only partially effective against the strains of the virus that were circulating when those vaccines were made, Adalja said.
However, BARDA is currently supporting two clinical trials with a candidate vaccine virus that “is a good match to what we found in cows,” Boucher said.
Flu vaccine makers are just getting started prepare the shots this fall but eventually the federal government could request that production be switched to a pandemic-targeted strain.
“We don't have the ability to do both,” Adalja said.
ASPR currently has a stockpile of pandemic vaccine in bulk and has identified manufacturing sites where 4.8 million doses could be bottled and finished without halting seasonal flu vaccine production, ASPR chief said, Dawn O'Connell, on May 22. American officials began to try to diversify. away from egg-based vaccines in 2005, when bird flu first gripped the world, and more vigorously after the 2009 fiasco. But “with the resources we have available, we get the best and the best value for American taxpayers when we take advantage of seasonal infrastructure, and that's still primarily egg-based,” Boucher said.
Flu vaccine companies “have a system that works well now to meet their goals in manufacturing the seasonal vaccine,” he said. And without any financial incentive, “I think we'll be here for a while with eggs.”
KFF Health News is a national newsroom that produces in-depth journalism on health issues and is one of the core operating programs of KFF — the independent source of health policy research, polling and journalism.
