FDA claims on COVID-19 vaccine safety are unsupported by reliable data – and could severely hinder vaccine access

Frank Han, University of Illinois Chicago The Food and Drug Administration is seeking to drastically change procedures for testing vaccine safety and approving vaccines, based on unproven claims that mRNA-based COVID-19 vaccines caused the death of at least 10 children. The agency detailed its plans in a memo released to staff on Nov. 28, 2025, which was obtained by several news outlets and published by The Washington Post. Citing an internal, unpublished review, the memo, written by the agency’s top vaccine regulator, Vinay Prasad, attributes the children’s deaths to myocarditis, an inflammation of the heart muscle. And it says the deaths were reported to the Vaccine Adverse Event Reporting System, or VAERS, but provides no evidence that the vaccines caused the deaths.  

COVID-19 vaccine safety

The death of children due to an unsafe vaccine is a serious allegation. I am a pediatric cardiologist who has studied the link between COVID-19 vaccines and heart-related side effects such as myocarditis in children. To my knowledge, studies to date have shown such side effects are rare, and severe outcomes even more so. However, I am open to new evidence that could change my mind. But without sufficient justification and solid evidence, restricting access to an approved vaccine and changing well-established procedures for testing vaccines would carry serious consequences. These moves would limit access for patients, create roadblocks for companies and worsen distrust in vaccines and public health. In my view, it’s important for people reading about these FDA actions to understand how the evidence on a vaccine’s safety is generally assessed.

Determining cause of death

The FDA memo claims that the deaths of these children were directly related to receiving a COVID-19 immunization. From my perspective as a clinician, it is awful that any child should die from a routine vaccination. However, health professionals like me owe it to the public to uphold the highest possible standards in investigating why these deaths occurred. If the FDA has evidence demonstrating something that national health agencies worldwide have missed – widespread child deaths due to myocarditis caused by the COVID-19 vaccine – I don’t doubt that even the most pro-vaccine physician will listen. So far, however, no such evidence has been presented. While a death logged in VAERS is a starting point, on its own it is insufficient to conclude whether a vaccine caused the death or other medical causes were to blame. To demonstrate a causal link, FDA staff and physicians must align the VAERS report with physicians’ assessments of the patient, as well as data from other sources for monitoring vaccine safety. These include PRISM, which logs insurance claims data, and the Vaccine Safety Datalink, which tracks safety signals in electronic medical records. It’s known that most deaths logged only in VAERS of children who recently received vaccines have been incorrectly attributed to the vaccines – either by accident or in some cases on purpose by anti-vaccine activists.

Heart-related side effects of COVID-19 vaccines

In his Substack and Twitter accounts, Prasad has said that he believes the rate of severe cardiac side effects after COVID-19 vaccination is severely underestimated and that the vaccines should be restricted far more than they currently are. In a July 2025 presentation, Prasad quoted a risk of 27 cases per million of myocarditis in young men who received the COVID-19 vaccine. A 2024 review suggested that number was a bit lower – about 20 cases out of 1 million people. But that same study found that unvaccinated people had greater risk of heart problems after a COVID-19 infection than vaccinated people. In a different study, people who got myocarditis after a COVID-19 vaccination developed fewer complications than people who got myocarditis after a COVID-19 infection. Existing vaccine safety infrastructure in the U.S. successfully identifies dangers posed by vaccines – and did so during the COVID-19 pandemic. Today, most COVID-19 vaccines in the U.S. rely on mRNA technology. But as vaccines were first emerging during the COVID-19 pandemic, two pharmaceutical companies, Janssen and AstraZeneca, rolled out a vaccine that used a different technology, called a viral vector. This type of vaccine had a very rare but genuine safety problem that was detected.

VAERS, the Vaccine Safety Datalink, clinical investigators in the U.S. and their European counterparts detected that these vaccines did turn out to cause blood clotting. In April 2021, the FDA formally recommended pausing their use, and they were later pulled from the market. Death due to myocarditis from COVID-19 vaccination is exceedingly rare. Demonstrating that it occurred requires proof that the person had myocarditis, evidence that no other reasonable cause of death was present, and the absence of any additional cause of myocarditis. These factors cannot be determined from VAERS data, however – and to date, the FDA has presented no other relevant data.

A problematic vision for future vaccine approvals

Currently, vaccines are tested both by seeing how well they prevent disease and by how well they generate antibodies, which are the molecules that help your body fight viruses and bacteria. Some vaccines, such as the COVID-19 vaccine and the influenza vaccine, need to be updated based on new strains. The FDA generally approves these updates based on how well the new versions generate antibodies. Since the previous generation of vaccines was already shown to prevent infection, if the new version can generate antibodies like the previous one, researchers assume its ability to prevent infection is comparable too. Later studies can then test how well the vaccines prevent severe disease and hospitalization. The FDA memo says this approach is insufficient and instead argues for replacing such studies with many more placebo-controlled trials – not just for COVID-19 vaccines but also for widely used influenza and pneumonia vaccines. That may seem reasonable theoretically. In practice, however, it is not realistic. Today’s influenza vaccines must be changed every season to reflect mutations to the virus. If the FDA were to require new placebo-controlled trials every year, the vaccine being tested would become obsolete by the time it is approved. This would be a massive waste of time and resources.

Also, detecting vaccine-related myocarditis at the low rate at which it occurs would have required clinical trials many times larger than the ones that were done to approve COVID-19 mRNA vaccines. This would have cost at least millions of dollars more, and the delay in rolling out vaccines would have also cost lives. Placebo-controlled trials would require comparing people who receive the updated vaccine with people who remain unvaccinated. When an older version of the vaccine is already available, this means purposefully asking people to forgo that vaccine and risk infection for the sake of the trial, a practice that is widely considered unethical. Current scientific practice is that only a brand-new vaccine may be compared against placebo. While suspected vaccine deaths should absolutely be investigated, stopping a vaccine for insufficient reasons can lead to a significant drop in public confidence. That’s why it’s essential to thoroughly and transparently investigate any claims that a vaccine causes harm.

Vaccine vs illness

To accurately gauge a vaccine’s risks, it is also crucial to compare its side effects with the effects of the illness it prevents. For COVID-19, data consistently shows that the disease is clearly more dangerous. From Aug. 1, 2021, to July 31, 2022, more than 800 children in the U.S. died due to COVID-19, but very few deaths from COVID-19 vaccines in children have been been verified worldwide. What’s more, the disease causes many more heart-related side effects than the vaccine does. Meanwhile, extensive evidence shows that COVID-19 vaccination reduces the risk of hospitalization by more than 70% and the risk of severe illness in adolescent children by 79%. Studies also show it dramatically reduces their risk of developing long COVID, a condition in which symptoms such as extreme fatigue or weakness persist more than three months after a COVID-19 infection. Reporting only the vaccines’ risks, and not their benefits, shows just a small part of the picture. Frank Han, Assistant Professor of Pediatric Cardiology, University of Illinois Chicago This article is republished from The Conversation under a Creative Commons license. Read the original article.

PFAS in pregnant women’s drinking water puts their babies at higher risk, study finds

Derek Lemoine, University of Arizona; Ashley Langer, University of Arizona, and Bo Guo, University of Arizona When pregnant women drink water that comes from wells downstream of sites contaminated with PFAS, known as “forever chemicals,” the risks to their babies’ health substantially increase, a new study found. These risks include the chance of low birth weight, preterm birth and infant mortality. Even more troubling, our team of economic researchers and hydrologists found that PFAS exposure increases the likelihood of extremely low-weight and extremely preterm births, which are strongly associated with lifelong health challenges.

What wells showed us about PFAS risks

PFAS, or perfluoroalkyl and polyfluoroalkyl substances, have captured the attention of the public and regulators in recent years for good reason. These man-made compounds persist in the environment, accumulate in human bodies and may cause harm even at extremely low concentrations. Most current knowledge about the reproductive effects of PFAS comes from laboratory studies on animals such as rats, or from correlations between PFAS levels in human blood and health outcomes. Both approaches have important limitations. Rats and humans have different bodies, exposures and living conditions. And independent factors, such as kidney functioning, may in some cases be the true drivers of health problems. We wanted to learn about the effects of PFAS on real-world human lives in a way that comes as close as possible to a randomized experiment. Intentionally exposing people to PFAS would be unethical, but the environment gave us a natural experiment of its own. We looked at the locations of wells that supply New Hampshire residents with drinking water and how those locations related to birth outcomes. We collected data on all births in the state from 2010 to 2019 and zoomed in on the 11,539 births that occurred within 3.1 miles (5 kilometers) of a site known to be contaminated with PFAS and where the mothers were served by public water systems. Some contamination came from industries, other from landfills or firefighting activities.

PFAS from contaminated sites slowly migrate down through soil into groundwater, where they move downstream with the groundwater’s flow. This created a simple but powerful contrast: pregnant women whose homes received water from wells that were downstream, in groundwater terms, from the PFAS source were likely to have been exposed to PFAS from the contaminated site, but those who received water from wells that were upstream of those sites should not have been exposed. Using outside data on PFAS testing, we confirmed that PFAS levels were indeed greater in “downstream” wells than in “upstream” wells. The locations of utilities’ drinking water wells are sensitive data that are not publicly available, so the women likely would not have known whether they were exposed. Prior to the state beginning to test for PFAS in 2016, they may not have even known the nearby site had PFAS.

PFAS connections to the riskiest births

We found what we believe is clear evidence of harm from PFAS exposure. Women who received water from wells downstream of PFAS-contaminated sites had on average a 43% greater chance of having a low-weight baby, defined as under 5.5 pounds (2,500 grams) at birth, than those receiving water from upstream wells with no other PFAS sources nearby. Those downstream had a 20% greater chance of a preterm birth, defined as before 37 weeks, and a 191% greater chance of the infant not surviving its first year. Per 100,000 births, this works out to 2,639 additional low-weight births, 1,475 additional preterm births and 611 additional deaths in the first year of life. Looking at the cases with the lowest birth weights and earliest preterm births, we found that the women receiving water from wells downstream from PFAS sources had a 180% greater chance of a birth under 2.2 pounds (1,000 grams) and a 168% greater chance of a birth before 28 weeks than those with upstream wells. Per 100,000 births, that’s about 607 additional extremely low-weight births and 466 additional extremely preterm births.

PFAS contamination is costly

When considering regulations to control PFAS, it helps to express the benefits of PFAS cleanup in monetary terms to compare them to the costs of cleanup. Researchers use various methods to put a dollar value on the cost of low-weight and preterm births based on their higher medical bills, lower subsequent health and decreased lifetime earnings. We used the New Hampshire data and locations of PFAS-contaminated sites in 11 other states with detailed PFAS testing to estimate costs from PFAS exposure nationwide related to low birth weight, preterm births and infant mortality. The results are eye-opening. We estimate that the effects of PFAS on each year’s low-weight births cost society about US$7.8 billion over the lifetimes of those babies, with more babies born every year. We found the effects of PFAS on preterm births and infant mortality cost the U.S. about $5.6 billion over the lifetimes of those babies born each year, with some of these costs overlapping with the costs associated with low-weight births. An analysis produced for the American Water Works Association estimated that removing PFAS from drinking water to meet the EPA’s PFAS limits would cost utilities alone $3.8 billion on an annual basis. These costs could ultimately fall on water customers, but the broader public also bears much of the cost of harm to fetuses. We believe that just the reproductive health benefits of protecting water systems from PFAS contamination could justify the EPA’s rule.

Treating PFAS

There is still much to learn about the risks from PFAS and how to avoid harm. We studied the health effects of PFOA and PFOS, two “long-chain” species of PFAS that were the most widely used types in the U.S. They are no longer produced in the U.S., but they are still present in soil and groundwater. Future work could focus on newer, “short-chain” PFAS, which may have different health impacts.

PFAS are in many types of products, and there are many routes for exposure, including through food. Effective treatment to remove PFAS from water is an area of ongoing research, but the long-chain PFAS we studied can be removed from water with activated carbon filters, either at the utility level or inside one’s home. Our results indicate that pregnant women have special reason to be concerned about exposure to long-chain PFAS through drinking water. If pregnant women suspect their drinking water may contain PFAS, we believe they should strongly consider installing water filters that can remove PFAS and then replacing those filters on a regular schedule. Derek Lemoine, Professor of Economics, University of Arizona; Ashley Langer, Professor of Economics, University of Arizona, and Bo Guo, Associate Professor of Hydrology, University of Arizona This article is republished from The Conversation under a Creative Commons license. Read the original article.