Even a peep of news about a new flu pandemic is enough to set scientists clucking about eggs.<\/p>\n

They worried about them in 2005, and in 2009, and they\u2019re worrying now. That\u2019s because millions of fertilized hen eggs are still the main ingredient in making vaccines that, hopefully, will protect people against the outbreak of a new flu strain.<\/p>\n

\u201cIt\u2019s almost comical to be using a 1940s technology for a 21^{st<\/sup>-century pandemic,\u201d said Rick Bright, who led the Health and Human Services Department\u2019s Biomedical Advanced Research and Development Authority (BARDA) during the Trump administration.<\/p>\n}

It\u2019s not so funny, he said, when the currently stockpiled formulation against the H5N1 bird flu virus requires two shots and a whopping 90 micrograms of antigen, yet provides just middling immunity. \u201cFor the U.S. alone, it would take hens laying 900,000 eggs every single day for nine months,\u201d Bright said.<\/p>\n

And that\u2019s only if the chickens don\u2019t get infected.<\/p>\n

The spread of an avian flu virus has decimated flocks of birds (and killed barn cats and other mammals). Cattle in at least nine states and at least three people in the U.S. have been infected, enough to bring public health attention once again to the potential for a global pandemic.<\/p>\n

As of May 30, the only confirmed human cases of infection were dairy workers in Texas and Michigan, who experienced eye irritation. Two quickly recovered, while the third developed respiratory symptoms<\/a> and was being treated with an antiviral drug at home. The virus\u2019s spread into multiple species over a vast geographic area, however, raises the threat that further mutations could create a virus that spreads from human to human through airborne transmission.<\/p>\n

If they do, prevention starts with the egg.<\/p>\n

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To make raw material for an influenza vaccine, virus is grown in millions of fertilized eggs. Sometimes it doesn\u2019t grow well, or it mutates to a degree that the vaccine product stimulates antibodies that don\u2019t neutralize the virus \u2014 or the wild virus mutates to an extent that the vaccine doesn\u2019t work against it. And there\u2019s always the frightening prospect that wild birds could carry the virus into the henhouses needed in vaccine production.<\/p>\n
\u201cOnce those roosters and hens go down, you have no vaccine,\u201d Bright said.<\/p>\n
Since 2009, when an H1N1 swine flu pandemic swept around the world before vaccine production could get off the ground, researchers and governments have been looking for alternatives. Billions of dollars have been invested into vaccines produced in mammalian and insect cell lines that don\u2019t pose the same risks as egg-based shots.<\/p>\n
\u201cEveryone knows the cell-based vaccines are better, more immunogenic, and offer better production,\u201d said Amesh Adalja, an infectious disease specialist at Johns Hopkins University\u2019s Center for Health Security. \u201cBut they are handicapped because of the clout of egg-based manufacturing.\u201d<\/p>\n
The companies that make the cell-based influenza vaccines, CSL Seqirus and Sanofi, also have billions invested in egg-based production lines that they aren\u2019t eager to replace. And it\u2019s hard to blame them, said Nicole Lurie, HHS\u2019 assistant secretary for preparedness and response under President Barack Obama who is now an executive director of CEPI, the global epidemic-fighting nonprofit.<\/p>\n
\u201cMost vaccine companies that responded to an epidemic \u2014 Ebola, Zika, covid \u2014 ended up losing a lot of money on it,\u201d Lurie said.<\/p>\n
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.<\/p>\n
Pfizer and Moderna are testing seasonal influenza vaccines made with mRNA, and the government is soliciting bids for mRNA pandemic flu vaccines, said David Boucher, director of infectious disease preparedness at HHS\u2019 Administration for Strategic Preparedness and Response.<\/p>\n
Bright, whose agency invested a billion dollars in a cell-based flu vaccine factory in Holly Springs, North Carolina, said there\u2019s \u201cno way in hell we can fight an H5N1 pandemic with an egg-based vaccine.\u201d But for now, there\u2019s little choice.<\/p>\n
BARDA has stockpiled hundreds of thousands of doses of an H5N1-strain vaccine that stimulates the creation of antibodies that appear to neutralize the virus now circulating. It could produce millions more doses of the vaccine within weeks and up to 100 million doses in five months, Boucher told KFF Health News.<\/p>\n
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 partly effective against strains of the virus that circulated when those vaccines were made, Adalja said.<\/p>\n
However, BARDA is currently supporting two clinical trials with a candidate vaccine virus that \u201cis a good match for what we\u2019ve found in cows,\u201d Boucher said.<\/p>\n
Flu vaccine makers are just starting to prepare this fall\u2019s shots but, eventually, the federal government could request production be switched to a pandemic-targeted strain.<\/p>\n
\u201cWe don\u2019t have the capacity to do both,\u201d Adalja said.<\/p>\n
For now, ASPR has a stockpile of bulk pandemic vaccine and has identified manufacturing sites where 4.8 million doses could be bottled and finished without stopping production of seasonal flu vaccine, ASPR chief Dawn O\u2019Connell said<\/a> on May 22. U.S. officials began trying to diversify away from egg-based vaccines in 2005, when avian flu first gripped the world, and with added vigor after the 2009 fiasco. But \u201cwith the resources we have available, we get the best bang for our buck and best value to U.S. taxpayers when we leverage the seasonal infrastructure, and that\u2019s still mostly egg-based,\u201d Boucher said.<\/p>\n
Flu vaccine companies \u201chave a system that works well right now to accomplish their objectives in manufacturing the seasonal vaccine,\u201d he said. And without a financial incentive, \u201cwe are going to be here with eggs for a while, I think.\u201d<\/p>\n
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