An outbreak of bird flu in dairy cows in the United States is leading to the development of new, next-generation mRNA vaccines (similar to COVID-19 vaccines) that are being tested in both animals and humans.
Next month, the U.S. Department of Agriculture will begin testing a vaccine developed by University of Pennsylvania researchers by administering it to calves. The idea: If vaccinating cows protects dairy workers, it could mean a reduced chance of the virus passing to humans and mutating in ways that encourage human-to-human spread.
Meanwhile. The U.S. Department of Health and Human Services is consulting with manufacturers about possible mRNA flu vaccines for humans that, if needed, could supplement the millions of avian flu vaccine doses currently in the government’s possession.
St. in Memphis “If there is an epidemic, there will be a huge demand for the vaccine,” said Richard Webby, an influenza researcher at St. Jude Children’s Research Hospital. “The more different (vaccine production) platforms that can respond to this, the better.”
The bird flu virus has been spreading among more animal species in many countries since 2020. The virus was detected in dairy cattle in the United States in March, although researchers had thought the virus might also be in cows since December. This week, the USDA announced it had been found in alpacas for the first time.
At least three people (all workers on farms with infected cows) were diagnosed with bird flu, but their illnesses were considered mild.
But previous versions of the same H5N1 flu virus were highly lethal to people in other parts of the world. Authorities are taking steps to be prepared in case the virus mutates to become more deadly or to spread more easily from person to person.
Traditionally, most flu vaccines have been made using an egg-based manufacturing process that has been used for more than 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 liquid is collected from eggs and used as the basis for vaccines; The killed or weakened virus primes the body’s immune system.
Instead of eggs, which are also vulnerable to supply constraints caused by bird flu, some flu vaccines are made in giant cell containers.
Officials say they already have two candidate vaccines for humans that appear to be compatible with the bird flu virus in U.S. dairy herds. The Centers for Disease Control and Prevention used circulating bird flu virus as a seed strain for themselves.
Federal health officials say the government has hundreds of thousands of vaccine doses in pre-filled syringes and vials and could run out within weeks if needed.
They also say they have bulk antigen that could produce about 10 million more doses that could be filled, completed and distributed within a few months. CSL Seqirus, which produces a cell-based flu vaccine, announced this week that the government had hired it to fill and finish about 4.8 million of those doses. U.S. health officials said this week that the study could be completed by the end of summer.
But flu vaccine production lines are already working on this fall’s seasonal vaccines; This work will need to be interrupted to produce millions more doses of bird flu vaccine. That’s why the government is pursuing another, faster approach: mRNA technology used to produce the primary vaccines used 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 an avian flu mRNA vaccine in very early stage testing in humans. Moderna confirmed in a statement that “we are in discussions with the US government about advancing our pandemic influenza candidate.”
Similar studies are ongoing at Pfizer. In December, company researchers gave human volunteers an mRNA vaccine against a strain of bird flu that was similar but not exactly the same as that found in cows. Researchers have since conducted a laboratory experiment exposing blood samples from those volunteers to the strain seen on dairy farms and saw “a notable increase in antibody responses,” Pfizer said.
As for the vaccine for cows, Penn immunologist Scott Hensley worked with mRNA pioneer and Nobel laureate Drew Weissman to produce experimental doses. Hensley said the vaccine is similar to the Moderna vaccine for humans.
In first-step testing, mice and ferrets produced high levels of bird flu virus-fighting antibodies after vaccination.
In another experiment, researchers vaccinated a group of ferrets and deliberately infected them with disease, and then compared what happened to unvaccinated ferrets. Hensley said all vaccinated animals survived, while unvaccinated animals did not.
“The vaccine was really successful,” said Webby, whose laboratory conducted this study in collaboration with Hensley last year.
The cow study will be similar to first-step tests initially done in smaller animals. The plan is to initially vaccinate about 10 calves, half with one dose and half with the other dose. Their blood will then be drawn and examined to investigate how much bird flu-fighting antibodies have been produced.
Hensley said the USDA study had to first determine the right dose for such a large animal, then test whether it protected them as well as it did in smaller animals.
“The thing that scares me the most is the amount of interaction between cattle and humans,” Hensley said.
“We’re not talking about an animal living on top of a mountain,” he said. “If this were a bobcat outbreak I would feel bad for the bobcats, but it’s not a major human risk.”
If a vaccine reduces the amount of virus in the cow, “we reduce the chance of a mutant virus eventually spreading in humans,” he said.
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