Next-generation vaccines could make the flu season less of a snot-filled nightmare—if they ever reach the public, that is. Trial data out this week shows that Pfizer’s mRNA-based flu vaccine performed markedly better than a traditional shot.
On Wednesday, researchers published the results of a Phase III trial on the vaccine, funded by Pfizer, in the New England Journal of Medicine. The experimental vaccine was significantly more effective at preventing flu than a standard vaccine, the researchers found. The vaccine appears to cause slightly more side effects than others, but there’s a bigger concern: It’s uncertain whether it will be approved in the U.S., given the government’s current skepticism and fearmongering around mRNA vaccine technology.
Better but with a catch
The trial involved more than 18,000 healthy adult volunteers in the U.S., South Africa, and the Philippines. It took place over the course of the 2022 to 2023 flu season. People were randomly assigned to receive a single dose of the experimental vaccine, dubbed modRNA, or Fluzone, a widely used inactivated flu vaccine made by Sanofi Pasteur. Both vaccines covered the four most common types of flu predicted to be circulating that season: two influenza A viruses and two influenza B viruses.
There were noticeably fewer confirmed cases of influenza in the modRNA group compared to the control vaccine group (57 vs 87), the study showed. Overall, the modRNA vaccine was 34.5% more effective at preventing flu-like illness. The experimental vaccine also appeared to generate a higher antibody response to the influenza A strains and a similar response to the influenza B strains (nearly every confirmed flu case in the study was caused by influenza A).
“This randomized trial showed that the modRNA vaccine provided both similar and improved prevention of a first episode of laboratory-confirmed influenza in adults between the ages of 18 and 64 years,” the study researchers wrote.
That added protection may come with some tradeoffs, however. People given modRNA reported more local reactions (70.1% vs. 43.1%) after their shot, such as injection site pain. They were also more likely to report systematic adverse events in general, such as fever (5.6% vs 1.7%).
This finding makes sense, since a vaccine’s adverse events are often linked to the immune response it generates. So a stronger immune response tends to cause more side effects. But while adverse events were more common in those who took modRNA, these events were still usually mild or moderate in severity. In the end, the study researchers concluded that the adverse event profiles of the two vaccines were similar.
The RFK Jr. wrinkle
All that said, the most serious hurdle to modRNA’s approval isn’t its potential side effects.
Robert F. Kennedy Jr., the current U.S. Secretary of Health and Human Services, and his allies have systemically undermined vaccines during the second Trump administration. Just this week, for instance, the Centers for Disease Control and Prevention changed its website to boost the debunked myth that they cause autism. But as much as Kennedy and his buddies may mistrust vaccines in general, they have an especially strong hatred for mRNA vaccines, the newest type of vaccine that first saw wide use during the covid-19 pandemic.
RFK Jr. has (wrongly) stated that the mRNA covid-19 shots developed by Pfizer and Moderna were the “deadliest” vaccines ever created, for instance. Anti-vaccination advocates have also falsely claimed that mRNA vaccines are gene therapies, that they make people magnetic, and that they’re causing an explosion in cases of “turbo cancer.”
These unsupported fears of mRNA vaccines have had real-world consequences. In May, Moderna delayed the approval application for its combination flu/covid-19 vaccine (which also seemed to show greater protection against flu) after the FDA asked for more data. In August, RFK Jr. also pulled $500 million in federal funding for mRNA vaccine research and development.
Contrary to claims from the anti-vaccination movement that mRNA vaccines are worse or more dangerous than other vaccines, this technology could actually strengthen our defenses against seasonal flu, and not just in terms of improved effectiveness. Since these vaccines typically take less time to tweak and produce than older types of vaccines, countries could wait longer to select the strains predicted to circulate during the season. That shortened lag could then prevent unexpected strains from causing a mismatch with the vaccine (a disastrous situation that’s now happening this winter).
Moderna has said that it will seek approval for its stand-alone flu shot next year. And given these latest results, Pfizer will undoubtedly apply for approval of its modRNA vaccine, too. Typically, both vaccines would seem to have an excellent chance of approval. But nothing is typical these days.
English (US) ·