Measles: Latest vaccination trends in US kids under 24 months

Background

Measles is among the most contagious human diseases and can lead to pneumonia, encephalitis, hospitalization, and death. Before the vaccine became available, nearly every child contracted it within their first 15 years of life. Between one to three in every 1,000 children who get measles will die from associated complications. 

The first dose of the measles vaccine is recommended between 12 to 15 months of age, with a second dose between 4 to 6 years of age. The CDC reports immunization coverage for children under 35 months (NIS-Child survey data) and at kindergarten entry (approximately 5 to 6 years of age). The NIS-Child survey data is comprehensive; however, the most recent data is from children born in 2021. 

We explore month-level first-time measles (MMR or MMRV) vaccination rates and compare our results (through February 2025) to rates reported by the CDC in the most recent NIS-Child survey data.

Methods

Using a subset of Truveta Data, we included a population of children who had an outpatient visit between the ages of 12 to 15 months (365 – 450 days) between January 2018 through February 2025. Children were also required to have at least one outpatient visit in their first year of life. 

First-time vaccination on schedule (prior to 15 months)

We identified children who received a measles vaccine (MMR or MMRV) and the age at which they received their first vaccine. Vaccination events recorded prior to age 6 months (182 days) were assumed to be erroneous and excluded.

We identified children who received a vaccine between 6 and 15 months (timing aligned with routine and outbreak/travel guidelines from the CDC). We plot the unadjusted monthly rates of vaccines administered per children with an outpatient encounter between 12 to 15 months. Children were only counted in one month. If they had multiple encounters between 12 to 15 months, the last was selected. All children who received the vaccine were plotted in the month of their 12 to 15-month visit, regardless of when they received the vaccine. We also plot data from CDC’s NIS-Child survey, which presents an annual rate of children who received one dose of the measles vaccine by 13 months (the last survey year represents children born in 2021). The CDC data are based on children’s birth year; therefore, the data were shifted one year forward to align with the data in this study.

We stratified the data by rural versus urban residency using the Federal Office of Rural Health Policy Data Files. A threshold of 0.3 was used in this study to differentiate between rural and urban status.  We calculated the unadjusted rate of children who received a vaccination by 15 months of age. We plot and describe the differences in vaccination status by residency.

Late first-time vaccine dose (prior to 24 months)

For subsequent analyses we required our initial population to also have an outpatient visit between 16 to 23 months of age prior to May 2024. For this population, we describe the children who received a measles vaccine late but prior to 24 months. We describe the overall rate of vaccination and compare to the CDC NIS-Child rates for children by 19 months.

Similar to the prior analysis, children were only counted once, and they were counted at the time of their 12 to 15 month visit. If a child had multiple visits in this range, they were counted at the last visit. The figure was truncated to only include data for children in the cohort that would have sufficient time to have a follow up.

For children who received a measles vaccine, we describe the distribution of ages at which children received their first vaccine each year.

Results

We included 685,604 children in the study.

First-time vaccination on schedule (prior to 15 months)

In 2024, the average yearly vaccination rate for children at 13 months was 58.9%. The rate of vaccination by 13 months increased from 61.9% in 2018 to 65.9% in 2020 before decreasing to 58.9% in 2024. The yearly unadjusted rates we observed are similar to the CDC NIS-Child results by 13 months (children born in 2021).

We also observe an additional 10.4% of children receive a first-time measles vaccine between 13 to 15 months across all years studied.

Within these data, by 15 months, 68.5% of children in 2024 received at least one measles vaccine dose, which is still within the CDC recommended window. This rate has decreased almost 10 percentage points since the 2020 rate of 77.2%. These data complement the CDC reports and suggest that although most children receive a first-time vaccine prior to 13 months, a substantial number receive a first-time vaccine after, but still within the guidelines.

Children living in both rural and urban locations followed similar trends; however, across the study period on average 75.0% of children in urban areas received one measles vaccine by 15 months, compared to 65.5% of children in rural areas. This means for 20 children living in an urban environment, about 15 would have received a first-time vaccine by 15 months, while for 20 children living in a rural environment, only 13 would have received a first-time vaccine prior to 15 months.

Late first-time vaccine dose (prior to 24 months)

561,549 children were included in the subsequent analysis. The average annual rate of vaccination for children by 23 months increased from 90.2% in 2018 to 92.4% in 2020, before decreasing to 84.9% in 2024. This means that for every 100 children, almost eight fewer children received a first-time measles vaccine in 2024 compared to 2020. The yearly unadjusted rates we present are similar to CDC NIS-Child results at 19 months (through birth year 2021).