Measles, a disease many thought was relegated to the history books, is making a dramatic and troubling comeback across the Americas in 2025. According to the Pan American Health Organization (PAHO), the number of confirmed measles cases has soared to 10,139 across ten countries as of August 8—a 34-fold increase compared to the same period in 2024. The resurgence is most pronounced in Canada, which leads the continent with 4,548 cases, particularly in provinces such as Alberta, British Columbia, Manitoba, and Ontario. The United States and Mexico are also grappling with significant outbreaks, with 1,356 and 3,911 cases respectively.
Health experts and officials are pointing squarely to one cause: declining vaccination rates. Across the region, only 79% of people have received the recommended two doses of the measles, mumps, and rubella (MMR) vaccine, a figure that falls well short of the 95% threshold needed to prevent outbreaks. In fact, PAHO reports that 71% of measles cases have occurred in unvaccinated individuals, with another 18% involving people whose vaccination status is unknown. "Measles is preventable with two doses of a vaccine, which is proven to be very safe and effective. To stop these outbreaks, countries must urgently strengthen routine immunization and conduct targeted vaccination campaigns in high-risk communities," said Dr. Daniel Salas, Executive Manager of the Special Program for Comprehensive Immunization at PAHO, in a recent press release.
The consequences of these gaps in immunization are not just numbers on a spreadsheet—they are measured in lives lost. Eighteen people have died from measles in the Americas so far this year: fourteen in Mexico, three in the United States, and one newborn in Canada who succumbed to a fatal congenital infection. Particularly heartbreaking is the toll among indigenous communities in Mexico, where the case-fatality rate is 20 times higher than in the general population, as highlighted by PAHO.
One of the most concerning aspects of the current outbreaks is their spread beyond previously affected groups. While initial clusters were often linked to under-vaccinated Mennonite communities, recent data indicates a growing number of cases outside these groups, signaling broader vulnerabilities. For instance, in Mexico, a mass vaccination campaign is underway in the state of Chihuahua—home to 93% of the country’s cases—targeting people aged six months to 49 years across 14 priority municipalities. Bolivia, Argentina, Belize, Brazil, Paraguay, Peru, and Costa Rica have also reported cases, with Paraguay becoming the latest country to declare an outbreak this year.
The United States, too, is facing challenges. Outbreaks have been recorded in 41 jurisdictions, mainly among under-vaccinated Mennonite populations. Although some states, like Texas and New Mexico, have not reported new cases since late July, the risk remains high as vaccination rates stagnate or decline. The Centers for Disease Control and Prevention notes that the number of adults over age 20 contracting measles has jumped from 77 in 2024 to 462 so far this year.
Zooming in on the local level, the situation in South Florida is particularly instructive—and alarming. Broward County, for example, saw its kindergarten vaccination rate plummet to 82.2% in the 2024-25 school year, the lowest level in 15 years. This is well below the 95% public health goal that experts say is necessary to prevent outbreaks. Palm Beach and Miami-Dade counties fare only slightly better, with rates of 89.8% and 91% respectively. Florida’s statewide average stands at 88.8%, lagging behind the national average of 93%.
Exemptions from vaccination are also on the rise. In Florida, 6.29% of kindergartners were exempted from vaccine requirements in 2024-25, compared to a national average of 3.6%. Some counties in the state report exemption rates as high as 15%. The majority of these exemptions are for religious reasons, and the Florida Department of Health notes that the proportion of children with new religious exemptions is increasing each month. As more children attend school unvaccinated, the risk extends not just to them but also to parents, older adults, and immunocompromised individuals.
The reasons behind these declining vaccination rates are complex but, according to local health experts, are deeply entwined with the aftermath of the COVID-19 pandemic. "There’s a lot of distrust in the health system," said Daniela Rodriguez, a Broward County mother of three, in an interview with the South Florida Sun Sentinel. "After COVID, people have gotten more educated about vaccines and have started questioning things that weren’t questioned before." Pediatricians across Florida report that parents are increasingly hesitant, seeking more information and expressing concerns about vaccine safety and effectiveness. "They want more discussion, and there should be discussion. Medicine should be about shared decision-making," said Dr. Michael Glazier, chief medical officer of Bluebird Kids Health in Tamarac.
This hesitancy is not without consequences. In February 2024, a measles outbreak at Manatee Bay Elementary School in Weston, Florida, spread to nine children, all under 14, after it was discovered that 33 of the school’s 1,067 students lacked at least one dose of the measles vaccine. No adults were affected in that outbreak, but the broader trend is worrisome. Dr. Lewis Nelson, dean of Florida Atlantic University’s Schmidt College of Medicine, cautioned, "When the rate trends down, [children] are at a higher risk and more susceptible to diseases that can cause morbidity or death."
The implications go beyond measles. Florida has reported a record number of whooping cough cases in 2025—over 1,100, compared to 391 in 2019. Health officials expect this trend to continue as vaccination rates remain low. Dr. Kathleen Mueller, a board member of the American Academy of Family Physicians, told Parents Magazine that vaccines are rigorously tested and undergo extensive safety checks before being offered to the public, countering the misinformation that has proliferated online.
PAHO is responding to the crisis by providing technical cooperation to affected countries, supporting surveillance, laboratory diagnostics, outbreak response, and vaccination campaigns. The organization urges countries to achieve and sustain high immunization coverage—at least 95% with two doses of a measles-containing vaccine—reinforce rapid response systems, and engage at-risk communities to address vaccine hesitancy. While PAHO does not recommend travel restrictions, it advises travelers, including children as young as six months in outbreak areas, to ensure they are vaccinated.
The Americas once celebrated the interruption of endemic measles transmission in 2016, a feat unmatched globally. That achievement is now at risk. As the virus exploits gaps in immunization, the region faces a stark reminder: diseases once thought conquered can return with a vengeance when vigilance wanes. The call for action is clear—strengthen vaccination efforts, rebuild trust, and protect the most vulnerable before history repeats itself on an even larger scale.
