Most of the flu virus used in vaccines is grown in eggs, but there are alternatives. The seasonal flu vaccine Flucelvax, produced by CSL Seqirus, is grown in a cell line derived in the 1950s from the kidney of a cocker spaniel. The virus used in the seasonal flu vaccine FluBlok, made by Protein Sciences, isn’t grown; it’s synthesized. Scientists engineer an insect virus to carry the gene for hemagglutinin, a key component of the flu virus that triggers the human immune system to create antibodies against it. That engineered virus turns insect cells into tiny hemagglutinin production plants.
And then we have mRNA vaccines, which wouldn’t require vaccine manufacturers to grow any virus at all. There aren’t yet any approved mRNA vaccines for influenza, but many companies are fervently working on them, including Pfizer, Moderna, Sanofi, and GSK. “With the covid vaccines and the infrastructure that’s been built for covid, we now have the capacity to ramp up production of mRNA vaccines very quickly,” says Hensley. This week, the Financial Times reported that the US government will soon close a deal with Moderna to provide tens of millions of dollars to fund a large clinical trial of a bird flu vaccine the company is developing.
There are hints that egg-free vaccines might work better than egg-based vaccines. A CDC study published in January showed that people who received Flucelvax or FluBlok had more robust antibody responses than those who received egg-based flu vaccines. That may be because viruses grown in eggs sometimes acquire mutations that help them grow better in eggs. Those mutations can change the virus so much that the immune response generated by the vaccine doesn’t work as well against the actual flu virus that’s circulating in the population.
Hensley and his colleagues are developing an mRNA vaccine against bird flu. So far they’ve only tested it in animals, but the shot performed well, he claims. “All of our preclinical studies in animals show that these vaccines elicit a much stronger antibody response compared with conventional flu vaccines.”
No one can predict when we might need a pandemic flu vaccine. But just because bird flu hasn’t made the jump to a pandemic doesn’t mean it won’t. “The cattle situation makes me worried,” Hensley says. Humans are in constant contact with cows, he explains. While there have only been a couple of human cases so far, “the fear is that some of those exposures will spark a fire.” Let’s make sure we can extinguish it quickly.
Read more from MIT Technology Review’s archive
In a previous issue of The Checkup, Jessica Hamzelou explained what it would take for bird flu to jump to humans. And last month, after bird flu began circulating in cows, I posted an update that looked at strategies to protect people and animals.
I don’t have to tell you that mRNA vaccines are a big deal. In 2021, MIT Technology Review highlighted them as one of the year’s 10 breakthrough technologies. Antonio Regalado explored their massive potential to transform medicine. Jessica Hamzelou wrote about the other diseases researchers are hoping to tackle. I followed up with a story after two mRNA researchers won a Nobel Prize. And earlier this year I wrote about a new kind of mRNA vaccine that’s self-amplifying, meaning it not only works at lower doses, but also sticks around for longer in the body.
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