by A bird flu outbreak in US dairy cows is prompting the development of new next-generation mRNA vaccines – similar to COVID-19 shots – that are being tested in both animals and humans.
Next month, the US Department of Agriculture is to begin testing a vaccine developed by University of Pennsylvania researchers by giving it to calves. The idea: If vaccinating cows protects dairy workers, it could mean less chance for the virus to jump into humans and mutate in ways that could encourage person-to-person spread.
Meanwhile. the US Department of Health and Human Services is talking to manufacturers about possible mRNA flu vaccines for humans that could, if necessary, supplement the millions of bird flu vaccine doses already in government hands.
“If there’s a pandemic, there’s going to be a huge demand for a vaccine,” said Richard Webby, an influenza researcher at St. Jude Children’s Research Hospital in Memphis. “The better the (vaccine manufacturing) platforms can respond to that.”
The bird flu virus has been spreading among more animal species in scores of countries since 2020. It was detected in US dairy herds in March, although investigators think it may have been in cows since December. This week, the USDA announced that it was found in alpacas for the first time.
At least three people – all workers on farms with infected cows – were diagnosed with bird flu, although the illnesses were thought to be mild.
But earlier versions of the same H5N1 flu virus have been very deadly to people in other parts of the world. Officials are taking steps to be prepared if the virus weakens in a more deadly way or enables it to spread more easily from person to person.
Traditionally, most flu vaccines are made through an egg-based manufacturing process that has been in use for over 70 years. It involves injecting a candidate virus into fertilized chicken eggs, which are incubated for several days to allow the viruses to grow. The fluid is removed from the eggs and used as the basis for vaccines, with killed or weakened virus priming the body’s immune system.
Apart from eggs – which are also at risk of supply constraints due to bird flu – some flu vaccines are made in giant vats of cells.
Officials say they already have two candidate vaccines for people who appear to be a good match for the bird flu virus in US dairy herds. The Centers for Disease Control and Prevention used the circulating bird flu virus as their seed strain.
The government has hundreds of thousands of vaccine doses in pre-filled syringes and vials that could probably go out in a few weeks, if needed, federal health officials say.
They also say they have a bulk antigen that could generate nearly 10 million additional doses that could be filled, finished and distributed in a few months. CSL Seqirus, which manufactures a cell-based flu vaccine, announced this week that it had been hired by the government to fill and complete about 4.8 million of those doses. The work could be done by the end of the summer, US health officials said this week.
But the production lines for flu vaccines are already working on seasonal shots this fall – work that would have to be interrupted to produce millions more doses of the bird flu vaccine. So the government is pursuing another, faster approach: the mRNA technology used to produce the primary vaccines deployed against COVID-19.
These messenger RNA vaccines are made using a small portion of genetic material from the virus. The genetic blueprint is designed to teach the body how to make a protein used to build immunity.
The pharmaceutical company Moderna already has a bird flu mRNA vaccine in very early human testing. In a statement, Moderna confirmed that “we are in discussions with the US government regarding the advancement of our pandemic influenza candidate.”
Similar work is underway at Pfizer. Company researchers in December gave human volunteers an mRNA vaccine against a strain of bird flu that is similar — but not exactly the same — to the one in cows. Since then, researchers conducted a laboratory experiment exposing blood samples from those volunteers to the pressure seen on dairy farms, and saw “significant increases in antibody responses,” Pfizer said in a statement.
For the cow vaccine, Penn immunologist Scott Hensley worked with mRNA pioneer and Nobel laureate Drew Weissman to produce the experimental doses. Hensley said the vaccine is similar to the Moderna one for humans.
In the first phase of testing, mice and ferrets produced high levels of antibodies that fought the bird flu virus after vaccination.
In another experiment, the researchers vaccinated one group of ferrets and deliberately infected them, and then compared what happened to unvaccinated ferrets. All the vaccinated animals survived and the unvaccinated animals did not, Hensley said.
“The vaccine was very successful,” said Webby, whose lab did that work last year in collaboration with Hensley.
The cow study will be similar to the first stage testing done on small animals. The plan is to initially vaccinate about 10 calves, half with one dose and half with another. Their blood will then be drawn and tested to see how many avian flu-fighting antibodies have been produced.
The USDA study will first have to determine the right dose for such a large animal, Hensley said, before testing whether it protects them as it did for smaller animals.
The thing that scares me the most is the amount of interaction between cattle and people,” Hensley said.
“We’re not talking about an animal that lives on top of a mountain,” he said.
If a vaccine reduces the amount of virus in the cow, “then we reduce the chance of a mutant virus emerging that spreads in humans,” he said.
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The Associated Press Health and Science Section is supported by the Howard Hughes Medical Institute Science and Media Education Group. The AP is solely responsible for all matters.
