Resurgence of Measles: Vaccine Misinformation at Work

“Pompous, uninformed bluster and proud ignorance based on ideology, not evidence, are running our country at the expense of innocent lives.”

Chloe Nazra Lee, MD, MPH, psychiatry resident, Department of Psychiatry, University of Rochester

“The primary cause of the resurgence in measles cases is failure to vaccinate, not failure of the vaccine.”

Lien Anh Do, MD, PhD and Kim Mulholland, MD, “Measles 2025,” New England Journal of Medicine, December, 2025

The measles vaccine, considered a gold standard vaccine, provides about 97% protection making measles a preventable disease. Not only is the measles vaccine highly effective, it is also safe. Due to vaccination programs, in 2000 the World Health Organization (WHO) declared measles had been eliminated from the U.S., that is, there was no longer continuous, endemic transmission within our country. Soon, that may no longer be the case.

As we enter 2026, measles continues its unwelcome resurgence across the U.S., and we are now on the verge of losing our measles elimination status. (Continuous circulation of a measles strain for a year qualifies as endemic transmission which undermines elimination.) This is due to declining vaccination rates and increasing vaccine hesitancy fueled not only by misinformation about vaccines on social media but also misinformation promulgated by diehard anti-science and anti-vaxx personalities like Robert F. Kennedy, Jr., Secretary of the U.S. Department of Health and Human Services (HHS). In this week’s post, I provide a report on the measles resurgence in our country.

What is measles (aka rubeola)? (recap) Morbillivirus hominis, the measles virus, is a single-stranded RNA virus belonging to the Paramyxoviridae family. A key feature of M. hominis is its virulence; it is the most contagious human pathogen. This is reflected in its high basic production number R~12-18, meaning one infected person can infect 12-18 others in a fully susceptible population. (As a basis for comparison, the R value of influenza virus is ~1-2 and that of SARS-Co-V-2 is ~2-3.)

Measles is highly contagious because it combines exceptionally efficient transmission with universal susceptibility of people who aren’t immune. The virus is transmitted by airborne particles (aerosols) when an infected person breathes, talks, coughs, or sneezes. Small-particle aerosols can remain infectious in the air and on surfaces for up to 2 hours. And high viral shedding occurs for up to four days before the rash or other symptoms develop.

Also, there is no pre-existing immunity or cross-immunity conferred by other viruses, meaning nearly 100% of non-immune people will become infected. Thus, the threshold for herd immunity against measles virus is at least 95% for any given human population. (This means that at least 95% of the population must have preexisting immunity as a result of previous infection or vaccination.)

Symptoms of measles include fever, maculopapular rash, and at least one other feature such as cough, conjunctivitis, or mucus from the nose. It can affect many organs, including the lungs (pneumonia), gastrointestinal tract (diarrhea), and nervous system. For every 1,000 children infected, one or two will die, often of pneumonia or encephalitis (brain infection).

The measle vaccine works; it prevents disease. Following the introduction of the first measles vaccine in 1963 and subsequent widespread vaccination efforts, measles cases in the U.S. fell dramatically. By the late 1970s, reported cases were 80% less than in the previous decade. A final major push in the 1990s, including the recommendation for a second dose of the measles, mumps, rubella (MMR) vaccine, further reduced the incidence to less than 1 case per million population by the end of the 21^st century. This led the WHO to declare measles eliminated from the United States in 2000.

The nadir (lowest point) for global measles cases occurred around 2020-2021, during the COVID-19 pandemic, when the reported incidence dropped significantly to 21 and then 17 per million people. This was also a period of naive optimism that measles could be sent to the same trash bin as that of smallpox, which remains the only human pathogen that’s been eradicated, defined as the “permanent reduction to zero of worldwide infection achieved through deliberate efforts, meaning that intervention measures are no longer needed.” 

Fast forward to 2024. The measles outbreak in Texas in early 2024 was a harbinger of a robust measles resurgence in the U.S. By July, 2025, the Centers for Disease Control and Prevention (CDC) reported that U.S. measles cases broke a 33-year record, achieving a “kind of a new normal.” By the end of 2025, U.S. measles cases topped 2,000 known infections. (The CDC’s figures as of January 6, 2026, show over 2,119 confirmed cases in 45 jurisdictions, with 93% occurring in unvaccinated individuals.)

The rise in U.S. cases—from a low of 13 in 2020 to 1,912 by the end of 2025—represented a whopping 14,608% increase.  This astounding increase in measles cases can be attributed in large part to an overall decline in childhood immunizations, like MMR, below the threshold level needed for herd immunity.

Leadership vacuum at a critical moment. The timing of this measles resurgence couldn’t be worse. At precisely the time when strong, science-based public health leadership is most needed, the U.S. is experiencing unprecedented disruption to its public health infrastructure.

The withdrawal from the WHO in early 2025 removed the U.S. from the primary international body coordinating global measles surveillance and vaccination efforts—the same organization that led the successful smallpox eradication campaign. This decision weakens not only global measles control efforts but also our own ability to detect and respond to reported cases.

Then there is Robert F. Kennedy, Jr.. Mr. Kennedy is responsible for the anti-science, anti-vaxx agenda at the HHS. At the beginning of Mr. Kennedy’s tenure at HHS, some thought he might “stumble onto the right answer a couple of times a day.” That didn’t happen. As Dr. N. Adam Brown recently wrote: “There is not much, if anything, Secretary Kennedy has done well in 2025. While he hides behind a smokescreen of small victories, the reality is that the intricate, complex, agency he is leading is not advancing. It is shattered, and it is the secretary and his cronies who have done the breaking. In doing so, he has placed generations of Americans at risk.” (N. Adam Brown, “I Was Wrong About RFK Jr.,”Medpage Today, December 20, 2025).

Early in his tenure at HHS, Mr. Kennedy dismantled the CDC’s Advisory Committee on Immunization Practices (ACIP), which for decades provided evidence-based guidance on vaccination policy. The “retirement” of all 17 ACIP expert members and their replacement with a panel that includes vaccine sceptics represents a dramatic departure from science-based public health policy. And, when leadership dismisses expertise and elevates ideology over evidence, the consequences will be measured in human suffering.

What can be done? The solution to our current measles resurgence is straightforward: we need to restore and maintain high vaccination rates. We have a safe, highly effective vaccine. We have the scientific understanding of how measles spreads and how to stop it. What we currently lack is the collective will and leadership to use these tools effectively.

In the end, the fight against measles is inseparable from the fight against misinformation, the fight for science-based policy, and the fight to maintain public trust in our health institutions. These battles will determine not only whether we can eliminate measles and someday even eradicate the disease, but whether we can protect the remarkable advances in human health that vaccination has made possible over the past century.