How Measles Came Roaring Back in a Single Generation, Pushing the US Toward Losing Elimination Status

In March 2000, the US Centers for Disease Control and Prevention convened a group of experts to talk about measles. Cases had been low for so long that the group could redefine the disease's standing in the country. Their conclusion was that measles was no longer endemic in the United States. It had not been wiped out entirely, but it was considered eliminated, and a precise definition of elimination would come later.

Dr. Yvonne Maldonado, a pediatric infectious diseases expert at Stanford University, was at that meeting representing the National Vaccine Advisory Committee. She remembers leaving with what she calls "cautious optimism." The country was doing well, she recalled, but should not rest on its laurels. With infectious diseases, she said, you can never be comfortable that the task is finished.

The committee members said much the same in their own summary, published in the Journal of Infectious Diseases in May 2004. They credited millions of parents and children, hundreds of thousands of health workers, and thousands of policy makers and legislators who supplied political and financial support. They also warned that the situation was inherently unstable. Immunization levels had to stay very high, surveillance had to be of high quality, and the US should support global measles control and work toward eventual global eradication.

Now the country is on the brink of losing the status it earned. Deadly outbreaks have pushed case counts to their highest level since the early 1990s. Authority over elimination status has since moved to an international advisory group appointed by the Pan American Health Organization, an arm of the World Health Organization. At a closed-door meeting this month, that committee will assess whether measles has spread locally and continuously in the US for at least a year, which would make it endemic again. Experts widely expect the US to lose its status, largely because vaccination rates have fallen for years.

Maldonado called the situation tragic, unnecessary and entirely preventable. Two doses of a safe and highly effective vaccine would essentially limit cases, she said, and the country is throwing that away. She argues that a culture of denial about measles has taken hold, along with vastly overstated and actively false claims about the vaccine's safety.

Regaining status is possible once the US shows that outbreak transmission has been interrupted for at least 12 months. Janet Hamilton, executive director of the Council of State and Territorial Epidemiologists, says it will be harder than the first time. Trust in public health and in science remains low, still damaged by the Covid-19 pandemic. And the epidemiology has shifted. When the push toward elimination began, adults were immune because they had all had measles as children, so efforts could focus on vaccinating children. Now immune protection lags in some pockets of adults too, and the approach will have to be very different. The public health system is also far less funded, resourced and supported than before.

Dr. Walter Orenstein, who has led the CDC's National Immunization Program, notes that large outbreaks have typically triggered pivotal policy changes. He points to presidential initiatives that provided resources and advocacy, including the Vaccines for Children Program and the National Childhood Immunization Initiative, which encouraged school mandates and state laws promoting mass immunization. "We've not seen that in this time," he said.

CDC Director Dr. Erica Schwartz said in November that the agency will not fundamentally change its outbreak response even if elimination status is lost. Health and Human Services Secretary Robert F. Kennedy Jr. has long doubted the safety and efficacy of the MMR vaccine. He has sought to reduce the number of childhood immunizations the federal government recommends, launched a federal program focused on vaccine injuries, and given a keynote address at a conference of Children's Health Defense, the advocacy group he founded. Medical experts say his rhetoric and actions have fueled falling vaccination rates.

Dr. Jonathan Temte, who attended the 2000 meeting for the American Academy of Family Physicians and is now professor emeritus at the University of Wisconsin, says leaders at the highest levels need to state plainly that MMR is effective and safe, that its side effects are known and mild, and that it does not cause autism. Until then, he said, getting on top of this will be hard.

Hamilton still sees advantages. No new vaccine is needed, since the current one is known to work, and far fewer people need vaccinating than in the past. Advances in behavioral science on what motivates change are also available. Success, she said, depends on how earnestly the country focuses on this moment.