Having access to accurate and evidence-based healthcare information is an essential ingredient for a well-functioning society in the 21st century. People rely on trusted sources to understand risks and make well-informed decisions for their health and that of their loved ones. As such, even subtle shifts in public-health messaging can have seismic effects. For instance, last week the U.S. Centers for Disease Control and Prevention (CDC) changed its website on "Autism and Vaccines."
The CDC's update claims that "The claim 'vaccines do not cause autism' is not an evidence-based claim because the studies have not ruled out that infant vaccines cause autism." The CDC did not update the website because there was a shift in the research that found something completely different, such as the case with smoking not being good for your health. No, this was merely a shift in messaging from an HHS Secretary with an axe to grind when it comes to vaccines. Needless to say, the Autism Science Foundation, Infectious Diseases Society of America, and Scientific American did not react positively to the change, and rightfully so. Before delving into what this debacle reveals about the CDC, it helps to start with the scientific reality of vaccines and autism itself.
The Scientific Consensus on Vaccines and Autism
In case it is not clear, it behooves us to iterate that decades of rigorous research has studied the topic and found that vaccines do not cause autism, as the American Academy of Pediatrics has illustrated. The National Academy of Medicine reviewed epidemiological data and found no association or causal mechanism between vaccines and autism (Casadevall, 2016). More recently, a large Danish study covering over 1 million children show that there is no link between aluminum in childhood vaccines and autism (Andersson et al., 2025).
The Burden of Proof and the CDC's Messaging
This piece today is not a treatise on the science of vaccines and autism, but is in part to show that the CDC doing is a classic sleight of hand by shifting burden of proof. While the CDC may claim to act out of precaution, its phrasing shifts the burden of proof unfairly and creates unnecessary fear. If someone claims that vaccines cause autism, they must be the ones to present evidence of that claim. Decades of research have been conducted and consistently found zero association, which means that the burden was met and failed. By saying that the link "has not been ruled out," it has developed a standard so vague that anything is possible. By that "logic," that would mean that Bigfoot, Santa Claus, or the Flying Spaghetti Monster are unresolved scientific questions simply because there is no evidence that disproves their existence with absolute metaphysical certainty. That is not how evidence-based research works, and that is certainly not how the CDC should communicate risk.
The CDC's History of Mistrust: The COVID Pandemic
Although the University of Minnesota said that the CDC is no longer trustworthy in light of this website change, I would argue that the CDC has not been trustworthy for a long while when it comes to disseminating evidence-based health information. If there was any time to show that the CDC could not be trusted with such a task, it was during the COVID pandemic. In 2021, I wrote a piece entitled Let's Go Back to Ignoring CDC and Federal Health Guidance Like We Always Have. As my piece shows, there were multiple missteps, but I will cover two today.
The first is with face masks. At the beginning of the pandemic, the CDC said face masks were unnecessary. Then in April 2020, the CDC did an about-face and pushed for face masks, even though the science did not change. I do not want to debate the details, but do want to point out that the CDC's approach increased public confusion while eroding trust when the guidance shifted.
The second is about school closures. As I illustrated as early as July 2020, schools did not need to close down during the pandemic. The CDC went into fear mode instead of realizing that children have low COVID transmission rates. As a result, the school closures delayed children's educational attainment while eroding their social and mental health for a statistically insignificant benefit, especially relative to the costs.
Other Historic Examples of CDC Risk Aversion and Bad Advice
The pandemic was not the only time that the CDC took missteps out of risk-aversion or fear. This trend has existed for a number of years and well before the pandemic. Here are a few examples of this phenomenon:
- Raw milk: The CDC has strongly warned against the consumption of raw milk. This zero-risk approach limits personal choice and voluntary risk management, which is something I advocated for in 2016.
- Blood donation of men who have sex with men (MSM): Since the 1980s, the CDC had consistently categorized MSM as a "high-risk" donor group and maintained conservative deferral recommendations even when modeling studies show that shorter deferrals would only minimal increase residual risk. By clinging onto the precautionary principle instead of assessing individual risk, what happened was that the CDC contributed to unnecessarily reducing the donor pool while increasing stigma of gay men.
- Zika travel bans: In 2016, the CDC recommended a blanket travel ban for pregnant women. It didn't matter that a CDC study showed that risk was minimal above 2,000 meters (Cetron, 2016). As a result of this zero-risk approach, it ended up having an impact on tourism upwards of $63.9 billion.
- West Nile Virus (WNV): In the early days of WNV (1999-2002), the CDC's guidance was highly risk-averse, emphasizing worst-case outcomes while recommending extensive outdoor avoidance and large-scale pesticide spraying. Aside from the insecticide-related illness caused by the spraying, the large-scale pesticide spraying diverted resources from other more targeted and sustainable measures (e.g., larval source reduction, biological control, trap-based adult mosquito control).
- Tuberculosis (TB): In the 1990s, the CDC recommended TB screening for all healthcare workers. This policy led to widespread unnecessary testing, strained resources, and minimal additional benefit in low-risk groups (e.g., Larsen et al., 2002). As a result, it prompted later revision to a risk-based strategy instead of a one-size-fits-all approach.
The Pattern of CDC Mismanagement
There are other examples of CDC incompetence. What I will say is that the CDC changing its "Autism and Vaccines" website is not an anomaly. It demonstrates how the CDC has mismanaged public health information over the years and how it is slow to update guidelines due to bureaucratic inertia. Recommendations should weigh both risks and benefits, and the CDC's embrace of the precautionary principle above else shows that it is incapable of doing so. This behavior shows how a top federal agency can mislead millions on scientifically proven topics and how healthcare can become propagandized.
When political influence seeps into scientific communication, it undermines public trust in scientific guidance. This certainly was the case when the Biden administration politicized the COVID vaccines, which resulted in the spillover effect of people having less trust in all vaccines. Plus, trust of various health authorities is in decline (KFF). The CDC's recent website change can make parents delay or avoid vaccines, which could increase the risk of preventable disease. More generally, this erosion of trust from the CDC can make matters more difficult in future disease outbreaks.
Recommendation: Reassessing CDC Authority
At a minimum, the CDC should have greater scrutiny and auditing to make sure its information is accurate. However, I do not think that is sufficient given its history because the CDC has proven time and again that federal government health messaging cannot be taken at face value. The CDC should go back to its original role of tracking and containing outbreaks of diseases. The CDC's mission creep is costing lives because precaution without nuance creates harm, easters resources, and erodes public trust. Having such a fallible institution in charge of providing evidence-based information is clearly not its forte.
If the CDC should not be in charge of providing public health directives, who should be? There is the possibility of entrusting it to private organizations. Alternatively, local- or state-level public health agencies can be responsible. At least that way, accountability is higher since the impact is more localized. Why is that the case?
Ultimately, public health guidance should be accurate, measured, and accountable. Centralizing authority in a single, risk-averse federal agency has shown time and again that even well-intentioned directives can produce harmful unintended consequences. By decentralizing responsibility, we can ensure that the guidance is closer to the populations it affects, is more transparent, and is more responsive to real-world risk (e.g., Rigby et al., 2024; Sessions, 2012). Only by aligning responsibility with accountability can we hope to provide public health recommendations that are both scientifically sound and practically effective, rather than by bureaucratic impulse or political whim.
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