Monday marks one full year of continued measles transmission in Canada, a milestone that will set the country back decades in its global health commitment. The ongoing transmission in the United States puts it among a group of countries that also face scrutiny from international leaders and risk a similar fate.
All World Health Organization regions have committed to eliminating measles by 2030, defined by the absence of local transmission of the virus for a period greater than 12 months. Canada achieved this goal in 1998, but falling vaccination rates set the stage for cases to become a massive (and ongoing) outbreak, putting the country and region at risk of losing elimination status.
In early November, the Pan American Health Organization, a regional office of WHO, will convene an annual meeting of its Regional Commission for Surveillance and Reverification of Measles and Rubella Elimination to formally determine the status of measles elimination throughout the region.
“A country is no longer considered measles-free if the virus returns and transmission continues continuously for more than a year,” the WHO said in a statement. “There are no formal consequences for losing measles elimination status; however, measles becoming an endemic disease again will have a profound negative impact on communities, including preventable deaths among some of the most vulnerable populations.”
Countries that lose elimination status will be asked to submit a corrective action plan, which may include efforts focused on intensified vaccination activities, enhanced surveillance, and rapid response to the outbreak.
In 2016, the Americas became the first and only region to effectively eliminate measles by ending local spread. Venezuela and Brazil have since lost elimination status, and were recently re-verified after years of “extensive vaccination, surveillance and rapid response efforts,” PAHO said. The region as a whole regained elimination status last year, but is once again under threat.
International travel was the initial source of the outbreak that began in Canada in October 2024, according to the Public Health Agency of Canada. But the country has now had thousands of cases in 10 jurisdictions, including hundreds of hospitalizations and two deaths of babies who were born prematurely with infections they contracted before birth.
Canada has counted more than 5,000 cases this year, more than double what the country has recorded in the last 25 years combined. All but 157 cases have been associated with the outbreak, and about 90% of all cases have occurred among unvaccinated people.
“Immunization coverage throughout the Region is insufficient to stop the emergence of outbreaks, and also hides pockets within countries that have even lower coverage. The Region needs to maintain high coverage, quality surveillance and a rapid response at all times,” the WHO stated.
Canadian leaders are “more consistent” in their support for vaccination than American leaders, said Dr. Dawn Bowdish, an immunologist and professor in the Department of Medicine at McMaster University in Ontario. National polls suggest the vast majority of parents still support childhood vaccination, he said, but disruptions to health care due to the Covid-19 pandemic, misinformation and liberal exemption rules in some provinces have created vulnerabilities.
The possibility of losing elimination status “highlights the severity of the measles outbreak,” Bowdish said. “If you look at the other countries that also have measles circulating, they are countries without strong public health, like Canada, and they are countries that have been torn apart by war or civil unrest. It’s an eye-opener on how you need to have constant vigilance and constant public health support to be able to fight infectious diseases.”
Canada’s national health agency says it is in regular communication with the Pan American Health Organization about the progress of the outbreak and efforts to contain it. The outbreak has slowed in recent weeks, the agency says, but 30 new cases were still reported in the last week of available data.
And Canada is not the only country that represents a risk to the region. Six others, including the United States and Mexico, have active measles transmission situations that will be discussed at the PAHO commission meeting. President Donald Trump issued an executive order in January to withdraw the United States from the WHO, but PAHO says it expects U.S. officials – from both the CDC and the National Sustainability Commission – to attend the commission’s meeting on measles elimination next month.
In August, local health officials declared an outbreak centered in West Texas, one of the largest and deadliest in decades, over. The outbreak caused 762 cases over the course of about seven months, according to state health department data; Neighboring New Mexico also reported 100 cases this year associated with the outbreak. Three people died: two children in Texas and an adult in New Mexico, all of them unvaccinated.
But measles counts continue to rise in the United States, and ongoing outbreaks in several states, including one on the Arizona-Utah border and another in South Carolina, are being investigated for possible connections to the Texas outbreak. If links are confirmed and cases continue to spread through January, the United States will also have lost its right to the measles elimination status it gained in 2000.
The US Centers for Disease Control and Prevention considers the elimination of measles a historic achievement, credited to a “highly effective vaccination program” in the United States and improved measles control throughout the Americas region.
But coverage with the measles, mumps and rubella (MMR) vaccine has been declining in the United States and Canada for years, with notable drops after the Covid-19 pandemic.
This past school year marked the fifth consecutive year that MMR coverage among kindergartners in the U.S. fell below the federal goal of 95%, a benchmark needed to prevent the spread of this highly contagious disease. And in Canada, data from six jurisdictions show that the proportion of 2-year-olds who had received at least one dose of MMR fell from nearly 90% in 2019 to less than 83% in 2023.
In South Carolina, there have been at least 22 cases associated with an outbreak in the northern region of the state, and more than 100 unvaccinated children were quarantined for weeks after a measles exposure at school. The state health department sent a mobile health unit to the area to offer the free MMR vaccine, but uptake has been lower than leaders expected: Only 21 people used the resource over the past week.
“While we are pleased that 21 people have chosen to receive the vaccine, the observed increase is largely attributed to adults, contributing less to herd immunity in school populations where we have seen the greatest spread so far during this outbreak,” Louis Eubank, director of the state health department’s Office of Emergency Preparedness and Response, said in an email. “We remain hopeful that more parents of unvaccinated children will make an informed decision to take advantage of this opportunity to protect their children from serious illness.”
The measles outbreak along the Arizona-Utah state line has grown to more than 100 cases since mid-August, spreading largely in unvaccinated communities. Last year, nearly 1 in 5 kindergartners in Utah’s southwestern district, where the outbreak is growing, lacked documentation of having received the MMR vaccine, more than in any other region and twice the state average.
As measles has spread across the country and locally, Utah public health officials report an increase in vaccinations: 32% more MMR vaccinations statewide between March and September than the same period last year. But vaccinations increased by only half in the Southwest District (up 16% year over year), contributing to widening coverage disparities.
Researchers at McMaster University say vaccine hesitancy is fueled by a “complex combination of personal, social and environmental factors.”
They said individual behaviors are influenced by the community, both in physical proximity and through social networks.
“This dynamic can also lead to localized pockets of undervaccination that benefit the unprotected through herd immunity, but also risk unvaccinated groups becoming high-risk groups if that protection deteriorates,” they wrote in a recent analysis published in The Conversation. “The COVID-19 pandemic has shown how harmful misinformation, misinformation, gaps and information gaps, including immunization coverage and vaccine hesitancy, can be to public health.”
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