Next-generation vaccines could make flu season less of a nightmare — if they ever reach the masses, that is. Trial data this week shows that Pfizer’s mRNA-based flu vaccine performed significantly better than the traditional shot.
On Wednesday, researchers published the results of a Phase 3 trial on the Pfizer-funded vaccine in the New England Journal of Medicine. Researchers found that the experimental vaccine was significantly more effective at preventing the flu than the standard vaccine. This vaccine appears to cause slightly more side effects than others, but there is one big concern: It is uncertain whether it will be approved in the US, given the government’s current skepticism and fear about mRNA vaccine technology.
better but with a catch
The trial involved more than 18,000 healthy adult volunteers in the US, South Africa and the Philippines. This occurred during the 2022 to 2023 flu season. People were randomly assigned to receive one dose of the experimental vaccine, called modRNA or Fluzone, a widely used inactivated flu vaccine made by Sanofi Pasteur. Both vaccines covered the four most common types of flu estimated to be circulating that season: two influenza A viruses and two influenza B viruses.
The study showed that there were significantly fewer confirmed cases of influenza in the modRNA group compared to the control vaccine group (57 vs. 87). Overall, the modRNA vaccine was 34.5% more effective at preventing flu-like illness. The experimental vaccine appeared to produce a high antibody response to influenza A strains and a similar response to influenza B strains (almost every confirmed flu case in the study was caused by influenza A).
“This randomized trial showed that the modRNA vaccine provided similar and superior prevention of a first episode of laboratory-confirmed influenza in adults aged 18 to 64 years,” the study researchers wrote.
However, the added security may come with some tradeoffs. People who were given modRNA reported more local reactions (70.1% vs. 43.1%) after the shot, such as pain at the injection site. They were also more likely to report common systemic adverse events, such as fever (5.6% vs. 1.7%).
This finding makes sense, as adverse events from a vaccine are often linked to the immune response it generates. Therefore a stronger immune response produces more side effects. But while adverse events were more common in those taking modRNA, these events were still generally mild or moderate in severity. Ultimately, study researchers concluded that the adverse event profiles of both vaccines were similar.
rfk jr wrinkles
All that said, the most serious obstacle to modRNA approval is not its potential side effects.
Current US Health and Human Services Secretary Robert F. Kennedy Jr. and his colleagues have systematically undermined vaccines during the second Trump administration. For example, just this week, the Centers for Disease Control and Prevention changed its website to promote the debunked myth that they cause autism. But as much as Kennedy and his friends may distrust vaccines in general, they have a particularly deep hatred of mRNA vaccines, the newest type of vaccine that first saw widespread use during the COVID-19 pandemic.
For example, RFK Jr. has (incorrectly) said that the mRNA COVID-19 shots developed by Pfizer and Moderna were the “deadliest” vaccines ever made. Anti-vaccination advocates have also falsely claimed that mRNA vaccines are gene therapy, that they magnetize people, and that they are causing an explosion in “turbo cancer” cases.
These unsupported fears about mRNA vaccines have had real-world consequences. In May, Moderna delayed the approval application for its combination flu/COVID-19 vaccine (which also showed greater protection against the 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 by the anti-vaccination movement that mRNA vaccines are worse or more dangerous than other vaccines, this technology could actually strengthen our protection against seasonal flu, and not just in terms of improved effectiveness. Because these vaccines typically take less time to modify and produce than older types of vaccines, countries may have to wait longer to select strains that are expected to circulate during the season. That short interval could then prevent unexpected strains from mismatching with the vaccine (a disastrous situation that is now happening this winter).
Moderna has said it will seek approval for its standalone flu shot next year. And given these latest results, Pfizer will undoubtedly apply for approval of its modRNA vaccine as well. Generally, both vaccines have a very good chance of being approved. But nothing is normal these days.