The strange reason flu shots have been so hard to improve

In August 2025, the Department of Health and Human Services halted 22 mRNA vaccine projects, valued at approximately $500 million, and announced the end of funding for this technology, following skepticism from former Health Secretary Robert F. Kennedy Jr. Despite his claims being incorrect, as Moderna had already published Phase 3 trial results, Kennedy's stance didn't change.

A year later, on August 5, 2026, the Food and Drug Administration (FDA) approved mFLUSIVA, the first mRNA influenza vaccine in the United States. This approval happened because of the FDA's predetermined deadline, set in February, after they initially rejected Moderna's application and later reversed their decision. The approval received little attention, partly due to seasonal flu's low priority among Americans – less than 50% of U.S. adults got their flu shot that year.

However, flu is serious, with the 2024-25 season causing 51 million illnesses, 710,000 hospitalizations, and 45,000 deaths. A better flu vaccine is crucial, but the real story is what this approval says about the year that produced it. The nine experts who unanimously approved the vaccine were appointed under Kennedy's watch, and their unanimous vote shows a change in perspective.

Flu vaccines have traditionally been grown in fertilized chicken eggs, a labor-intensive process that takes six months. This results in a mismatch between the flu strain in the vaccine and the one circulating in November, making the vaccine less effective. The mRNA vaccine, on the other hand, skips this step and can be developed much faster, reducing the time from strain selection to finished vaccine from six months to two to three months.

This platform technology has shown promise in other areas, such as melanoma and pancreatic cancer treatments, where mRNA therapy has significantly improved patient survival rates. While these successes are not specific to the flu vaccine, the underlying technology and its rapid development potential are important for future public health advancements.

After Kennedy's decision, Americans have fallen behind in accessing new flu vaccines, such as Moderna's combined Covid-and-flu shot, which is already licensed in Europe while Americans await a resubmission.