Vaccinate Your Family partner organization Voices for Vaccines publishes weekly explainers to help make sense of trending claims about vaccines. Vaccinate Your Family will be sharing curated myth busting posts to help explain trending topics in respiratory vaccines during the winter season.
Adapted with credit to Voices for Vaccines. Originally published February 13, 2025
The Claim
A circulating video featuring RFK Jr. suggests that the flu vaccine “weakens” the immune system through something called “pathogenic priming,” making people more likely to get other infections. It points to a supposed 36 percent increase in coronavirus illness and claims that ingredients such as mercury, aluminum, and formaldehyde are harmful and cause long-term health issues.
The Facts
Several studies were shared alongside the video:
1. Department of Defense study
The video claims this study shows that the flu shot “primes you for coronavirus.” In reality, the study’s conclusion states the opposite. It found no increased risk of other viral infections among people who received the flu vaccine. In fact, the flu shot was linked to strong protection, including against illnesses like parainfluenza and RSV. The Department of Defense continues to require flu vaccination for service members.
2. Study claiming “4.4 times more illness”
One of the cited studies involved 115 children, and the video’s narrator highlights this portion while ignoring the rest. The same study also evaluated nearly 6,000 adults and found that flu vaccination was associated with fewer non-flu respiratory infections.
This selective use of data is a common tactic used to spread misinformation.
3. Claim that the flu vaccine “enhances” coronavirus infection
The referenced study does not show this. Instead, the flu vaccine did not increase the risk of COVID-19 infection or severity. Vaccines work by training the immune system to respond more effectively, not by making infections worse.
4. “Pathogenic priming”
The article cited on this topic was written in 2020 by a well-known anti-vaccine figure, before any COVID-19 vaccines existed. Its claims are not supported by clinical evidence. Decades of real-world data and clinical trials show that vaccines help prevent severe illness and are a cornerstone of public health.
The strongest available evidence shows that the flu shot does not weaken the immune system. Instead, flu vaccines help your body mount a quicker, stronger response to real infections. Claims that they increase susceptibility to other viruses rely on outdated theories and misinterpretations of research, not credible science.
Science continues to advance, and our understanding may have evolved since the original publication. For the most up-to-date information, explore the latest Just the Facts topics at Voices for Vaccines.
Content adapted from Voices for Vaccines with credit to their “Just the Facts” series.