Even a little bit of news about a new flu pandemic is enough to make scientists cackling over eggs.
They worried about it in 2005 and 2009, and they worry now. That’s because millions of fertilized chicken eggs are still the key ingredient in making vaccines that will hopefully protect people against the outbreak of a new strain of flu.
“It’s almost comical to use 1940s technology for a 21st century pandemic,” said Rick Bright, who led the Health and Human Services Department’s Biomedical Advanced Research and Development Authority during the Trump administration.
It’s not that funny, he said, when the currently stored formulation against the H5N1 bird flu virus requires two injections and as much as 90 micrograms of antigen, yet provides only mediocre immunity. “For the US alone, chickens would have to lay 900,000 eggs every day for nine months,” Bright said.
And that’s only if the chickens do not get infected.
The spread of a bird flu virus has decimated flocks of birds (and killed barn cats And other mammals). Livestock in at least nine states and at least two people in the U.S. have been infected, enough to refocus public health attention on the potential for a global pandemic.
The only one so far confirmed human cases of the infection included dairy workers in Texas and Michigan, both of whom suffered from pink eye and recovered quickly. But the spread of the virus to multiple species over a vast geographic area raises the threat that further mutations could create a virus that spreads from person to person through the air and causes respiratory infections.
If they do, prevention starts with the egg.
To make raw material for a flu vaccine, the virus is grown in millions of fertilized eggs. Sometimes it doesn’t grow properly, or it mutates to an extent that the vaccine product stimulates antibodies that don’t neutralize the virus – or the wild virus mutates to an extent that the vaccine doesn’t work against it. And there is always the frightening prospect that wild birds could carry the virus into the chicken coops needed for vaccine production.
“Once those roosters and chickens go down, you don’t have a vaccine anymore,” Bright said.
Since 2009, when an H1N1 swine flu pandemic swept the world before vaccine production could get off the ground, researchers and governments have been looking for alternatives. Billions of dollars have been invested in vaccines produced in mammalian and insect cell lines, which do not carry the same risks as egg-based vaccinations.
“Everyone knows that the cell-based vaccines are better, more immunogenic and have better production,” said Amesh Adalja, an infectious disease specialist at the Center for Health Security at Johns Hopkins University. “But they are handicapped because of the impact of egg-based production.”
The companies that make the cell-based flu vaccines, CSL Seqirus and Sanofi, have also invested billions in egg-based production lines that they are reluctant to replace. And it’s hard to blame them, said Nicole Lurie, HHS assistant secretary for preparedness and response under President Barack Obama, who is now executive director of CEPI, the global nonprofit epidemic control organization.
“Most vaccine companies that responded to an epidemic — Ebola, Zika, COVID — ended up losing a lot of money on it,” Lurie said.
Exceptions were the mRNA vaccines created for COVID, although 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 administration is soliciting bids for mRNA pandemic flu vaccines, said David Boucher, director of infectious disease preparedness at the HHS Administration for Strategic Preparedness and Response.
Bright, whose agency invested $1 billion in a cell-based flu vaccine factory in Holly Springs, North Carolina, said there is “no way we can fight an H5N1 pandemic with an egg-based vaccine.” But for now there is little choice.
BARDA has stockpiled hundreds of thousands of doses of a vaccine of the H5N1 strain that stimulates the production of antibodies that appear to neutralize the virus now circulating. It could produce millions of additional doses of the vaccine within weeks and up to 100 million doses within 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 shots containing six times as much vaccine substance as typical flu shots, the stockpiled vaccines were only partially effective against the virus strains circulating when those vaccines were made, Adalja said.
However, BARDA is currently supporting two clinical trials with a vaccine virus candidate that “fits well with what we found in cows,” Boucher said.
The makers of flu vaccines are just getting started prepare this fall’s photos but ultimately the federal government could request production be switched to a pandemic-targeted strain.
“We don’t have the capacity to do both,” Adalja said.
For now, ASPR has a stockpile of pandemic vaccine in bulk and has identified production sites where 4.8 million doses can be bottled and finished without halting production of the seasonal flu vaccine, ASPR chief Dawn O’Connell said on May 22. American officials began to diversify. away from egg-based vaccines in 2005, when bird flu first gripped the world, and with extra vigor after the 2009 fiasco. But “with the resources we have at our disposal, we get the best value for our money and the best value for American taxpayers when we take advantage of the seasonal infrastructure, which is still largely egg-based,” Boucher said.
Flu vaccine companies “have a system that is currently working well to achieve their goals in producing the seasonal vaccine,” he said. And without a financial incentive, ‘we’re going to be stuck here for a while, I think.’
KFF Health News is a national newsroom that produces in-depth journalism on health issues and is one of its core operating programs KFF – the independent source for research, polls and journalism in the field of health policy.
