Instead, roughly three in ten adults occupy a "mixed middle"—a group characterized by uncertainty and inconsistent beliefs—which public health experts identify as a critical demographic for targeted, accurate communication.
Understanding the "Mixed Middle" in Vaccine Beliefs
Public health polling by KFF reveals that consistent belief in debunked vaccine claims remains low, with fewer than one in ten adults labeling common myths as "definitely true." These myths include false assertions that MMR vaccines cause autism, that measles vaccines are more dangerous than the disease itself, or that mRNA technology can alter human DNA.
The KFF data categorizes public sentiment into a typology:
- Consistent Myth Deniers (29%): Adults who consistently reject all four major vaccine myths.
- Leaned Myth Deniers (26%): Those who lean toward rejecting the myths but express some uncertainty.
- The Mixed Middle (31%): Individuals who lack firm conviction, providing a mix of "probably true" or "probably false" responses across various claims.
- Myth Believers (7%): A small minority who consistently or partially accept these false narratives.
According to KFF, this "mixed middle" is more prevalent among younger adults, Black and Hispanic populations, Republicans, and those without a college education. Furthermore, regular users of social media and AI chatbots for health information are more likely to fall into this uncertain category than those who do not use these platforms.
The Role of AI in Public Health Communication
As health departments seek cost-effective ways to improve vaccination rates, researchers are testing the efficacy of artificial intelligence. A study published in JAMA Network Open recently evaluated whether AI chatbots could effectively encourage HPV vaccination among parents.
The findings showed that while brief interactions with an AI chatbot increased parents’ stated intent to vaccinate immediately, those effects faded within 45 days. In contrast, traditional written public health materials maintained their impact over the same period. Neither method significantly increased actual vaccination rates, suggesting that logistical barriers—such as scheduling pediatrician appointments—remain a primary hurdle that technology alone cannot overcome.
mRNA Technology and Public Perception
Public uncertainty regarding mRNA technology continues to be a focal point for health agencies. Following a unanimous recommendation by an FDA advisory committee to approve a Moderna mRNA-based influenza vaccine for adults 50 and older, misinformation has circulated online.
Despite social media claims that the technology alters DNA or poses widespread health risks, global data from over 6 billion administered doses supports the safety profile of mRNA vaccines. KFF polling indicates that while exposure to the "DNA alteration" myth has declined by 9 percentage points since April 2025, a significant portion of the public remains unsure about the technology. Because many people report not knowing enough about mRNA to judge its safety, clear communication about the scope of the FDA’s recommendation—which applies only to one specific flu vaccine and does not replace traditional options—is essential to prevent unnecessary vaccine hesitancy.
Scientific Independence and Agency Trust
Public confidence in federal health institutions remains a challenge. KFF polling shows that fewer than 40% of adults are confident that agencies like the CDC and FDA make decisions based strictly on science, independent of outside interests or personal views.
This skepticism is often fueled by high-profile internal disputes. For instance, a CDC-led study on COVID-19 vaccine effectiveness—which found the vaccine reduced hospitalizations and emergency visits by at least 50%—faced delays in publication after being pulled from the Morbidity and Mortality Weekly Report (MMWR) due to methodological disagreements. While the study was eventually published in a medical journal, such public friction over research methods can undermine the perceived credibility of the surveillance tools used to monitor vaccine safety and effectiveness.
For parents who currently skip or delay childhood vaccines, this climate of uncertainty is particularly impactful. Nearly half of parents who delay vaccinations fall into the "mixed middle," suggesting that their behavior is driven more by confusion than by a firm ideological rejection of medical science. Providing consistent, clear, and accessible information remains the primary strategy for addressing this uncertainty.