Harvard Study Shows Flu Shots Prevent 9-14 Cases Per 100 Kids, June 02

A Harvard Medical School study published in JAMA Pediatrics found that for every 100 children vaccinated against influenza, 9 to 14 cases are prevented. The research arrives as President Trump issued an executive order directing federal agencies to align with a January HHS study that recommends removing the flu vaccine from standard childhood immunizations. A federal court blocked this change in March, but the administration is appealing.

New Evidence on Vaccine Effectiveness

Researchers at Harvard analyzed five influenza seasons from 2016 to 2023, using birth months as a natural experiment. Children born in fall have higher vaccination rates because they see doctors around their birthdays when the flu shot becomes available in mid-August. Children born in summer often need separate appointments to get vaccinated. The study found that 50.8% of kids aged 2 to 5 born between September and November received the flu shot during the 2022-23 season. In the United States, preventing 9 to 14 cases per 100 vaccinated children means hundreds of thousands or even a million cases avoided each year, according to study author Anupam Jena.

Trump Directs Agencies to Narrow Vaccine List

On June 1, President Trump signed an executive order directing federal agencies to align with an HHS study that calls for cutting childhood vaccine recommendations. The study recommends vaccinating all children against 11 diseases. Flu, rotavirus, hepatitis A, hepatitis B, some forms of meningitis, and RSV would move to “shared decision-making” between doctors and parents, meaning they become optional rather than routine. The order tells the CDC to “provide maximum flexibility to parents and doctors” and directs all federal agencies to update regulations and funding to match the narrower schedule. The order states Americans retain access to all vaccines.

Court Blocks Earlier Attempt, Appeal Pending

The Trump administration previously tried to remove the flu vaccine from CDC recommendations in January. A federal judge in Massachusetts blocked that change in March, ruling against the removal. The administration is appealing the decision. Meanwhile, some states have begun creating their own alliances to counter Trump’s vaccine guidance. States, not the federal government, have authority to require vaccinations for schoolchildren, though CDC recommendations often influence state rules. The CDC removed the flu vaccine from its recommended list in January, citing lack of evidence that it prevents serious illness and deaths in children.

Researchers Respond With Data

Harvard researchers said they published their findings specifically because the federal government cited an absence of evidence when removing the flu vaccine from recommendations. Christopher Worsham, an assistant professor at Massachusetts General Hospital and co-author, stated: “The federal government cited an absence of evidence that they want to see, and so we have provided that.” The study analyzed data from children aged 2 to 5 and found consistent vaccine effectiveness across multiple seasons. The 2024-25 flu season resulted in 280 pediatric deaths in the United States.

Final Thoughts

Harvard’s data shows flu vaccines prevent significant illness in children, directly contradicting the Trump administration’s push to make them optional. The policy clash between federal agencies and courts will likely continue as states decide their own vaccination rules.

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