Measles Cases Surge Amid Declining Vaccination Rates

As confirmed measles cases continue to rise in the US, concerns are growing over declining vaccination rates.

Measles cases surge in the US as vaccination rates decline, raising concerns about outbreaks and public health under Robert F. Kennedy Jr.'s leadership. | Image Credit: Leigh Prather - stock.adobe.com

Measles Cases Surge Across US

As of May 1, the CDC reported 935 confirmed measles cases within 30 jurisdictions: Alaska, Arkansas, California, Colorado, Florida, Georgia, Hawaii, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Michigan, Minnesota, Missouri, Montana, New Jersey, New Mexico, New York City, New York State, Ohio, Oklahoma, Pennsylvania, Rhode Island, Tennessee, Texas, Vermont, Virginia, and Washington.¹

However, according to NBC News, David Sugerman, MD, MPH, a senior scientist leading the CDC’s measles response, told the agency’s vaccine advisory committee last month that many cases go unreported.²

To date, there have been 12 outbreaks, with 93% of confirmed cases (n = 869) linked to one of them.¹ Most confirmed cases (96%) have occurred in unvaccinated individuals or those with an unknown vaccination status. Additionally, the largest age group affected has been those aged 5 to 19 years (38%; n = 353).

Overall, 13% (n = 121) of individuals with confirmed cases have been hospitalized, with highest hospitalization rate in those under age 5 (23%; n = 66). There have also been 3 confirmed measles-related deaths.

The Ongoing Danger of Measles

Although the CDC declared measles eliminated from the US in 2000, it remains common in many parts of the world.³ Consequently, each year, it is brought into the country by unvaccinated travelers after being infected abroad; these travelers are mostly Americans but are sometimes international visitors.

Measles is highly contagious. If one person has it, 9 out of 10 people nearby can become infected if unprotected. Typically, symptoms appear 7 to 14 days after exposure. They include high fever, cough, runny nose, conjunctivitis, and a rash.

The disease can lead to serious health complications, especially in children younger than 5 years old. Common complications include ear infections and diarrhea, but serious complications are encephalitis and pneumonia.

Declining Vaccination Rates Threaten Herd Immunity

According to the CDC, the best protection against measles is the measles, mumps, and rubella (MMR) vaccine, as it provides long-lasting defense against all strains of the disease. Despite this, the rate of kindergarteners with complete records for the MMR vaccine, along with those against polio, whooping cough, and chickenpox, has fallen from 95% before the COVID-19 pandemic to under 93% after it ended.⁴

This small decrease is creating new areas across the US that are no longer protected by herd immunity. In particular, Alaska, Florida, Idaho, Minnesota, Montana, South Dakota, and Wisconsin have seen at least 10% drops in vaccination rates among kindergarteners from 2023 to 2024.

Concerns surrounding the rise in preventable diseases, including measles, continue to grow following the appointment of Robert F. Kennedy Jr, a longtime vaccine skeptic, as HHS secretary.⁵ Although he has publicly urged people to get the measles vaccine, he maintains that it is a personal choice and should not be mandated by the government.⁶

“The federal government’s position, my position, is that people should get the measles vaccine, but the government should not be mandating those,” Kennedy said in an interview with CBS News last month. “I always said during my campaign—and every part, every public statement I’ve made—I’m not gonna take people’s vaccines away from them. What I’m gonna do is make sure that we have good science so that people can make an informed choice.”

Model Predicts Major Measles Outbreaks if Vaccination Rates Continue to Fall

If childhood vaccination rates continue to decline, millions of preventable infections, including measles, are likely to occur, according to a study recently published in JAMA.⁴ Using a state-level simulation model, researchers projected outcomes for measles, rubella, poliomyelitis, and diphtheria over 25 years under various vaccination scenarios.

In 2024, childhood vaccine coverage varied by state, with 88% to 96% for MMR, 78% to 91% for diphtheria-tetanus-pertussis, and 90% to 97% for inactivated poliovirus. Based on current rates, the model predicted 2550 deaths and 170,200 hospitalizations, with most infected with measles (851,300 cases).

Specifically for measles, the researchers found that increasing MMR coverage by just 5% to 10% would reduce measles cases to 5800 and 2700, respectively. A 10% drop, however, could lead to 11.1 million measles cases. If vaccination rates continue to fall, measles is projected to become endemic again within 21 years.

Overall, the researchers determined that maintaining or increasing vaccine coverage significantly reduced disease burden and delayed or prevented the return of endemic transmission.

“These findings support the need to continue routine childhood vaccination at high coverage to prevent resurgence of vaccine-preventable infectious diseases in the US,” the authors concluded.

References

1. Measles cases and outbreaks. CDC. May 2, 2025. Accessed May 8, 2025. https://www.cdc.gov/measles/data-research/index.html
2. Bendix A. CDC says measles cases are most likely underreported as outbreak swells in Texas. NBC News. April 16, 2025. Accessed May 8, 2025. https://www.nbcnews.com/health/health-news/cdc-measles-cases-missed-texas-us-rfkjr-rcna201426
3. About measles. CDC. May 29, 2024. Accessed May 8, 2025. https://www.cdc.gov/measles/about/index.html
4. Jeremias S. Falling vaccine coverage threatens a surge in preventable diseases. AJMC^®. April 24, 2025. Accessed May 8, 2025. https://www.ajmc.com/view/falling-vaccine-coverage-threatens-a-surge-in-preventable-diseases
5. Mattina C. Robert F. Kennedy Jr confirmed as HHS secretary, nearly along party lines. AJMC. February 13, 2025. Accessed May 8 2025. https://www.ajmc.com/view/robert-f-kennedy-jr-confirmed-as-hhs-secretary-nearly-along-party-lines
6. Freiman J. RFK Jr. encourages people to get measles vaccine in first network TV interview since becoming health secretary. CBS News. April 8, 2025. Accessed May 8, 2025. https://www.cbsnews.com/news/rfk-jr-measles-vaccine/?ftag=CNM-00-10aab4i