Measles was officially eliminated from the U.S. in 2000. The country still retains this status, but rates are climbing. In July 2026, the Centers for Disease Control and Prevention (CDC) released an update announcing the number of cases confirmed this year has topped 2,300, surpassing 2025’s record and securing a new 35-year high. And the year is only just halfway over.

This, it appears, may be part of a much wider global trend. A perspective published in PLOS Medicine tracks the resurgence of vaccine-preventable diseases, including measles, polio, and diphtheria, in parts of the world where they were once eliminated.

The Return of Measles

Eighty years ago, almost all children in the U.S. contracted measles before their fifteenth birthday. According to figures from the CDC, approximately 500 people died, and almost 50,000 were hospitalized every year as a result. But things changed in the early 1960s when a vaccine was introduced, causing cases to plummet and (eventually) for the U.S. to achieve measles elimination status in 2000.

However, over the last two years, the country has seen a dramatic rise in measles cases. In 2025, there were 2,289 confirmed cases. This year (2026), that figure has already been surpassed — the CDC reported 2,318 cases and 35 outbreaks as of July 23, 2026.

The U.S. is not the only case to see the return of measles. Between 2025 and 2026, seven countries lost their World Health Organization (WHO) measles elimination status, including the U.K. and Spain, according to studies in BMJ and PubMed.

Will the U.S. join them? The country is due to have its status reassessed in November, and it will depend on whether the outbreaks were importations from other countries or whether there has been within-country transmission, according to the WHO.

“I think we really need to start taking this [seriously] at a country,” Shaun Truelove, Associate Research Professor in the Department of International Health and Department of Epidemiology at Johns Hopkins, told Discover.

“Given what we have seen, with continued transmission in many states, and the likely seeding of outbreaks from one state to another, I think the challenge for this review will be to prove that the U.S. has not lost its elimination status, rather than to prove that it has,” Truelove, who did not take part in the research, added.

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The Resurgence Of Other Vaccine-Preventable Diseases

It’s not just measles. The researchers explain that several other vaccine-preventable diseases are making a comeback. In Southeast Africa, an outbreak of wild poliovirus type 1 occurred very shortly after the region was declared free of the virus in 2020. Thankfully, it has since been contained, but it was particularly notable for the virus’ decades-long absence from the region prior to the outbreak.

Meanwhile, in West Africa, a multi-country diphtheria outbreak is reversing progress towards eliminating the disease in the region. The paper’s authors attribute this rise, at least in part, to declining immunization rates.

What Is Behind the Resurgence?

The authors point to declines in vaccine coverage and hesitancy regarding uptake of the measles-mumps-rubella (MMR) vaccine, which has been targeted by misinformation campaigns and politicization. According to figures published by the CDC, vaccine coverage in U.S. kindergarteners has fallen from 95.2 percent in 2019 to 2020 to 92.5 percent in 2024 to 2025.

Globally, there have been declines in vaccine coverage thanks to a number of factors. These include COVID-related disruptions to immunization programs, access barriers and hesitancy. Combined, the researchers say, they increase the risk of disease outbreaks and the likelihood of vaccine-eliminated disease returning, which will lead to preventable illness and death that disproportionately affects the young.

Which Diseases Are Most Likely To Make A Comeback (And Where)?

This risk is higher in more transmissible diseases, such as measles.

According to the CDC, up to 90 percent of those who come into close contact with someone who has measles will contract the disease if they themselves are not protected (either from immunization or past infection). It, therefore, requires a higher degree of herd immunity than a disease, like influenza, that is less transmissible.

Another factor is how common a disease is globally. Re-emergence requires re-introduction of the pathogen, which tends to occur when an individual returns from a country where the disease is endemic. Measles is more common than poliovirus, which means measles is more likely to be re-introduced than polio.

The researchers explain this means outbreaks are most likely to occur when there is a combination of high importation and high susceptibility. In the U.S., for example, it may mean some regions are more at risk than others. This, they explain, offers the opportunity to develop targeted policy interventions.

As for whether the current resurgence of measles (and other vaccine-preventable diseases) is a temporary setback or a growing trend, the researchers say it remains to be seen.

As for what is happening in the U.S., Truelove warns that measles is a “canary in the coal mine” for vaccine-preventable diseases — because it is so transmissible, it is often the first noticed. Declines in other vaccines are leading to increased cases and outbreaks of diseases like pertussis, mumps, and chickenpox.

“We made immense strides globally in vaccination in the last century and reduced the burden of infectious diseases by millions of cases, deaths, and hospitalizations,” said Truelove. “Unfortunately, because of this success, much of our population, both in the U.S. and globally, no longer has personal experience with these diseases and has a hard time recognizing the risk."

This article is not offering medical advice and should be used for informational purposes only.

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Article Sources

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:

• This article references information from a study published in PLOS Medicine:Re-emergence of vaccine-preventable diseases in the post-elimination era
• This article references information from the CDC: Measles Cases and Outbreaks
• This article references information from the CDC: History of Measles
• This article references information from the CDC: About Measles
• This article references information from a study published in BMJ: UK loses its measles elimination status
• This article references information from a study published in PubMed: Measles outbreak in an occupational setting: challenges to regain elimination status for Spain, 14 January to 11 April 2026
• This article references information from the WHO: Update on the review of measles elimination status