Fact Check: CDC Study Does NOT Prove Pfizer COVID Vaccine Increases Infection Risk In Young Children

Did a Centers for Disease Control and Prevention study find that children who received the Pfizer COVID-19 vaccine are more likely to get infected than those who are unvaccinated? No, that’s not true: The study of children aged six months to four years found there was not a big difference in infection rates, especially for those who hadn’t had COVID before, but that is not the same as a finding that vaccination increases infection risk. The study also noted that COVID vaccines are recommended to prevent serious illness.

The claim appeared in a post (archived here) published on Instagram on December 22, 2024, under the on-screen title “‘Bombshell’ CDC Study: Kids Who Got Pfizer Vaccine More Likely Than Unvaccinated to Get COVID Infection.” The post’s caption said:

Pushing this for kids was one of the most starkly naked abuses of power and greed I have ever seen. My heart breaks for every child whose parents were tricked into thinking this was the right thing to do.

Thankfully the receipts are coming in (if you aren’t satisfied yet, more is coming) and the darkness of the machine has been exposed. As long as we don’t forget what happened here, it will never happen again ✊❤️‍🔥

And for the parents it was the most bombastic global propaganda campaign in history, don’t be hard on yourself if you were fooled 🙏 Have faith it will all be okay

This is what the post looked like on Instagram at the time of writing:

(Source: Instagram screenshot taken on Thu Jan 1 16:31:03 2024 UTC)

The post includes a screenshot of an article (archived here) from “The Defender,” a publication of Children’s Health Defense, an organization started by Robert F. Kennedy Jr. that’s known for advocating that parents not have their children vaccinated.

The post doesn’t provide any proof to back up its assertion that the study found kids who got the Pfizer COVID vaccine are more likely to catch COVID than unvaccinated kids.

The study

The study (archived here) cited in “The Defender” article, “Protection From COVID-19 Vaccination and Prior SARS-CoV-2 Infection Among Children Aged 6 Months – 4 Years, United States, September 2022 – April 2023,” was published on December 5, 2024, and supported by the CDC.

The “Discussion” section of the study notes a small sampling of data that may support the claim in the headline of “The Defender” article, but the results are inconclusive. It said:

Interestingly, among participants without evidence of prior infection, those vaccinated with Pfizer-BioNTech were more likely to have SARS-CoV-2 infection and COVID-19 compared to those who were naïve [someone who has not had the disease] and unvaccinated. … Further research is needed to assess vaccine effectiveness against infection for this age group for updated 2023-2024 vaccines. …

The major limitation of this study was the lack of sample size which precluded us from estimating vaccine effectiveness and adjusting for all potential confounders, such as the proportion of circulating variants and 7-day incidence average by site, daycare attendance, and whether household members tested positive for SARS-CoV-2. Other limitations of this study, most notably, the potential for missed prior infection detections due to waning of anti-N SARS-CoV-2 antibodies …

Considering all the statistics, the study authors reached these conclusions (emphasis ours):

Despite the limitations, data from this community cohort of young children with any SARS-CoV-2 infections and symptomatic COVID-19 disease contribute to understanding protection from vaccination and prior infection. COVID-19 vaccines are recommended to reduce severe illness; the overall risk of infection may not differ substantially between vaccinated and unvaccinated naïve children <5 years.

Bottom line: This study helps us understand how vaccines and past COVID infections protect young kids. COVID vaccines are recommended to prevent serious illness, but the chance of getting infected might not be very different for vaccinated and unvaccinated kids under 5 who haven’t had COVID before.

Pfizer

In a January 2, 2025, email to Lead Stories, Pfizer Media Relations responded to the claim in the Instagram post. A Pfizer spokesperson said:

Our data pre- and post-licensure have been, and are, extensively reviewed by multiple regulatory and advisory bodies around the world. Pfizer and BioNTech’s COVID-19 vaccines have been administered to billions of adults, adolescents and children, generating robust data demonstrating a favorable safety profile and high level of protection against severe COVID-19 disease and hospitalization.

The Pfizer spokesperson continued:

We continue to believe that broad vaccination programs are an essential tool for preventing COVID-19, especially COVID-19-associated hospitalizations and severe disease. Authorization of this season’s vaccine gives families the option to further protect their young children against circulating sublineages [variants].

The CDC recommends (archived here) that everyone six months and older get an updated COVID-19 vaccine.

Read more

Additional Lead Stories fact checks of claims about vaccines can be found here.

Other Lead Stories fact checks of claims involving Robert F. Kennedy Jr. can be found here.