CDC Warns of “Renewed Threat” to Measles Elimination Based on Increased Cases

The risk of widespread measles transmission in the US remains low though efforts are needed to increase routine measles, mumps, and rubella (MMR) vaccination coverage, according to the Centers for Disease Control and Prevention’s (CDC) Morbidity and Mortality Weekly Report.

A total of 338 cases of measles have been reported in the US between January 1, 2020 and March 28, 2024, with 29% (n=97) of cases occurring in the first quarter of 2024. Almost all of these cases were in individuals who were unvaccinated (68%) or did not know their vaccine status (23%) and had either traveled internationally or were around someone who traveled internationally (96%).

The median patient age was 3 years (range: 0 to 64 years), with more than half of the cases occurring in individuals 16 months through 19 years. Among those were not vaccinated or had unknown vaccination status (n=309), 84% were eligible for vaccination. Hospitalization occurred in 46% of cases (n=155), 70% of which occurred in patients less than 5 years old. There were no measles-related deaths reported to the CDC.

Because of high population immunity (based on data through the end of 2023), the risk of widespread measles transmission continues to remain low, the report authors noted. However, the increase in cases in 2024 suggests a “renewed threat to elimination” and the need for additional efforts to encourage MMR vaccination. 

“Rapid detection of cases, prompt implementation of control measures, and maintenance of high national measles vaccination coverage, including improving coverage in undervaccinated populations, is essential to preventing measles and its complications and to maintaining US elimination status,” the authors concluded. 

In the US, M-M-R II and Priorix are recommended for active immunization for the prevention of measles, mumps, and rubella. The CDC considers these vaccines to be fully interchangeable for MMR vaccination.