The bird flu vaccine is made with eggs. That has scientists worried.

Even news about a new flu pandemic it’s enough to leave scientists clucking over the eggs.

They worried about them in 2005 and in 2009, and they’re worried now. This is because millions of fertilized chicken eggs are still the main ingredient in the production of 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 Department of Health and Human Services’ Biomedical Advanced Research and Development Authority during the Trump administration.

It’s not so funny, he said, when the currently stockpiled formulation against H5N1 bird flu virus it requires two injections and a whopping 90 micrograms of antigen, but provides average immunity. “For the U.S. alone, it would require chickens laying 900,000 eggs every day for nine months,” Bright said.

And that’s only if the chickens are not infected.

The spread of the bird flu virus has flocks of birds decimated (and dead barn cats It is other mammals). Cattle in at least nine states and at least two people in the U.S. have been infected, enough to once again draw public health attention to the potential for a global pandemic.

So far, the only confirmed human cases The main cases of infection were dairy workers in Texas and Michigan, who suffered conjunctivitis and recovered quickly. However, the spread of the virus in multiple species over a wide geographic area increases the threat that new 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 produce raw materials 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 frightening prospect that wild birds could carry the virus into chicken coops needed to produce vaccines.

“Once these roosters and hens are down, you won’t have a vaccine,” Bright said.

Since 2009, when an H1N1 swine flu pandemic swept the world before vaccine production could begin, 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 pose the same risks as egg-based shots.

“Everyone knows that cell-based vaccines are better, more immunogenic and offer better yield,” said Amesh Adalja, an infectious disease expert at the Johns Hopkins University Center for Health Security. “But they are harmed because of the influence of egg-based manufacturing.”

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 unwilling 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 epidemic-fighting nonprofit.

“Most vaccine companies that responded to an epidemic — Ebola, Zika, COVID — ended up losing a lot of money on it,” Lurie said.

The exceptions were the mRNA vaccines created for COVID, although even Pfizer and Moderna have had to destroy hundreds of millions of doses of unwanted vaccines as public interest has waned.

Pfizer and Moderna are testing seasonal flu vaccines made with mRNAand the government is soliciting proposals for mRNA vaccines against pandemic flu, said David Boucher, director of infectious disease preparedness at HHS’s Administration for Strategic Preparedness and Response.

Bright, whose agency has invested a billion dollars 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 stored hundreds of thousands of doses of a vaccine against 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 weeks and up to 100 million doses in five months, Boucher told KFF Health News.

But the vaccines currently in national stockpiles are not a perfect match for the strain in question. Even with two shots containing six times more vaccine substance than typical flu vaccines, the stockpiled vaccines were only partially effective against the strains of the virus that were circulating when these vaccines were produced, Adalja said.

However, BARDA is currently supporting two clinical trials with a vaccine candidate virus that “is a good match to what we found in cows,” Boucher said.

Flu vaccine manufacturers are just beginning to prepare this fall’s photos but eventually, the federal government could request that production be shifted 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 manufacturing sites where 4.8 million doses could be bottled and finished without disrupting seasonal flu vaccine production, ASPR said. chief Dawn O’Connell said on May 22nd. U.S. officials began trying to diversify away from egg-based vaccines in 2005, when bird flu first took hold of the world, and with greater vigor after the 2009 fiasco. we have available, we get the best possible return and the best value for U.S. taxpayers when we leverage seasonal infrastructure, and that’s still primarily egg-based,” Boucher said.

Flu vaccine companies “have a system that works well right now to meet their objectives in manufacturing the seasonal vaccine,” he said. And without financial incentive, “we’ll stay here with eggs for a while, I think.”

KFF Health News is a national newsroom that produces in-depth journalism on health issues and is one of the main operational programs of the KFF — the independent source of research, polls and journalism on health policy.