Increase in Measles Cases Tied to Drop in Vaccination Rates

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Feb. 23, 2024 – The recent growth in measles cases in the United States and the world is linked to declining vaccination rates for children, medical experts say.

The CDC issued an alert last month saying 23 confirmed cases of measles had been detected in the United States between Dec. 1, 2023, and Jan. 23. That included seven cases imported by international travelers and two outbreaks with more than five cases each.

“Most of these cases were among children and adolescents who had not received a measles-containing vaccine (MMR or MMRV), even if age eligible,” the CDC said.

Vaccination rates have been declining for several years.

National coverage for measles, mumps, and rubella (MMR) was 93.1% for the 2022-2023 school year, a 2% drop from the 95% rate in the 2019-2020 school year, the CDC reported. That was the third straight year the rate fell below 95%, which is the level needed for herd immunity.

“We’re not just seeing cases, we’re seeing transmission, which means vaccine levels aren’t what we’d like them to be,” Saskia Popescu, PhD, an assistant professor of epidemiology and public health at the University of Maryland School of Medicine, told PBS

Another expert said that vaccine hesitancy fueled during the pandemic has also affected measles vaccination rates. 

 "In addition, because children were quarantined during the pandemic, many missed out on well-child visits and didn’t catch up on their vaccines. That has meant 61 million fewer doses distributed nationwide between 2020 and 2022," said Priya Soni, MD, a pediatric infectious disease specialist with Cedars-Sinai Guerin Children’s. 

The same trends are occurring globally. From 2021 to 2022, worldwide measles cases increased by 18%, and deaths have increased by 43%, the CDC and the World Health Organization reported.

“The increase in measles outbreaks and deaths is staggering, but unfortunately, not unexpected given the declining vaccination rates we’ve seen in the past few years,” said John Vertefeuille, PhD, director of the CDC’s Global Immunization Division. 

“Measles cases anywhere pose a risk to all countries and communities where people are under-vaccinated. Urgent, targeted efforts are critical to prevent measles disease and deaths.”