01/06/2024 – 10:08
The outbreak of avian influenza in dairy cows in the United States is prompting the development of new next-generation mRNA vaccines – similar to vaccines against Covid-19 – which are being tested in both animals and people.
Next month, the U.S. Department of Agriculture will begin testing a vaccine developed by researchers at the University of Pennsylvania, giving it to calves.
The idea: If vaccinating cows protects farmworkers, it could mean less chance of the virus jumping to people and mutating in ways that could drive human-to-human spread.
Meanwhile, the U.S. Department of Health and Human Services has been talking to manufacturers about possible mRNA flu vaccines for people that, if necessary, could supplement millions of doses of bird flu vaccine already in the government’s hands.
“If there is a pandemic, there will be a huge demand for vaccine,” says Richard Webby, a flu researcher at St. Jude Children’s Research Hospital in Memphis. “The more different vaccine manufacturing platforms that can respond to this, the better.”
The bird flu virus has been spreading among more animal species in dozens of countries since 2020. It was detected in dairy herds in the United States in March, although researchers believe it may have been in cows since December.
This week, the United States Department of Agriculture announced that it has been found in alpacas, a species of mammal, for the first time.
At least three people – all workers on farms with infected cows – were diagnosed with bird flu, although the illnesses were considered mild. But earlier versions of the same H5N1 flu virus were highly lethal to humans in other parts of the world.
This third case is the first of a person experiencing respiratory symptoms, including coughing, sore throat and watery eyes, which generally increases the likelihood of transmission to others, federal officials said Thursday.
Officials are taking steps to be prepared in case the virus mutates in a way that makes it more deadly or allows it to spread more easily from person to person.
Traditionally, most flu vaccines are 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 fluid is harvested from eggs and is used as the basis for vaccines, with dead or weakened viruses priming the body’s immune system.
Instead of eggs – also vulnerable to supply constraints caused by bird flu – some flu vaccines are made in large cell fermenters.
Officials say they already have two vaccine candidates for people that appear to be a good match for the bird flu virus in U.S. dairy herds. The Centers for Disease Control and Prevention (CDC) used the circulating bird flu virus as the seed strain for them. The government has hundreds of thousands of vaccine doses in prefilled syringes and vials that could likely be distributed in a matter of weeks if necessary, according to federal health officials.
They also say they have bulk antigen that could generate nearly 10 million more doses that could be filled, finished and distributed in a matter of a few months. CSL Seqirus, which makes cell-based flu vaccine, announced this week that the government has contracted it to fill and finish about 4.8 million of those doses. The work could be done by the end of summer [no Hemisfério Norte]US health officials said this week.
However, flu vaccine production lines are already working on this fall’s seasonal vaccines — work that would have to be halted to produce millions more doses of the bird flu vaccine. So the government has pursued 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 section of genetic material from the virus. The genetic blueprint is designed to teach the body how to make a protein used to build immunity.
Pharmaceutical company Moderna already has an mRNA vaccine against bird flu in very early-stage human trials. In a statement, the company confirmed that “we are in discussions with the US government regarding the advancement of our pandemic influenza vaccine candidate.”
Similar work has been carried out at Pfizer. Company researchers in December administered an mRNA vaccine to volunteers against a strain of bird flu that is similar to – but not exactly the same as – the one in cows. Researchers have since conducted a laboratory experiment exposing blood samples from these volunteers to the strain seen on dairy farms, and saw a “remarkable increase in antibody responses,” Pfizer said in a statement.
As for the vaccine for cows, Penn immunologist Scott Hensley worked with mRNA pioneer and Nobel laureate Drew Weissman to produce the experimental doses. Hensley says this vaccine is similar to Moderna’s for people.
In initial tests, mice and ferrets produced high levels of antibodies fighting the bird flu virus after vaccination.
In another experiment, researchers vaccinated a group of ferrets and deliberately infected them, and then compared what happened to ferrets that hadn’t been vaccinated. All the vaccinated animals survived and the unvaccinated ones did not, says Hensley.
“The vaccine was really successful,” reports Webby, whose lab did this work last year in collaboration with Hensley.
The cow study will be similar to the first-step tests initially done on smaller animals. The plan is to initially vaccinate around 10 calves, half with one dose and half with another. Your blood will then be drawn and tested to see how much bird flu-fighting antibodies have been produced.
The U.S. Department of Agriculture study will first have to determine the right dose for such a large animal, Hensley says, before testing whether it protects them as it did for smaller animals.
“What scares me most is the amount of interaction between livestock and humans,” he adds.
“We’re not talking about an animal that lives on top of a mountain,” he says. “If it was a bobcat outbreak, I would feel bad for the bobcats, but it doesn’t pose a huge human risk.”
If a vaccine reduces the amount of virus in the cow, “then ultimately we reduce the chance that a mutant virus that spreads in humans will emerge,” he says. /AP
This content was translated with the help of Artificial Intelligence tools and reviewed by our editorial team.
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