I2. Pediatric Vaccines
Oral Abstract Submission
Measles, a vaccine-preventable viral illness that can cause serious complications, was declared eliminated from the United States in 2000 because of a successful measles vaccination program. Recent years have seen an increase in the number of measles cases and outbreaks. We summarized measles epidemiology in the U.S. during 2017-2019.
We reviewed U.S. national surveillance data on confirmed measles cases reported to the Centers for Disease Control and Prevention during January 1, 2017-April 26, 2019. We describe the demographic characteristics, vaccination status, and disease epidemiology of measles cases.
During 2017-April 2019, 1196 measles cases were reported in 37 U.S. States and Washington D.C., including 146 (12%) importations from 37 countries; 108 (74%) of importations were U.S. residents returning from travel abroad, of which 60 (56%) were unvaccinated and 31 (29%) had unknown vaccinations status. Among 1148 cases who were U.S.-residents, the highest incidence of measles was among infants and children aged 6-11 and 12-15 months (112 cases [19 cases/million person-years] and 106 cases [27 cases/million person-years], respectively). Among U.S.-resident cases, 846 (74%) were unvaccinated and 163 (14%) had unknown vaccination status; 777 (68%) were considered to have preventable measles (i.e., were eligible for vaccination but unvaccinated). Among the 1196 cases, 85 were single cases, and the remaining 1111 represented 19 two-case chains and 34 outbreaks of 3 or more cases linked epidemiologically; the median outbreak size and duration was 6 cases (range, 3 to 452 cases) and 19.5 days (range, 5 to 205 days). A total of 934 (78%) of the 1196 cases and 13 (38%) of the 34 outbreaks occurred in underimmunized close-knit communities; eight outbreaks are ongoing.
Outbreaks of measles in the United States result from recurring measles introductions and subsequent measles spread, especially in underimmunized close-knit communities. To sustain measles elimination, it will be necessary to maintain timely routine high coverage with MMR vaccine, improve implementation of pre-travel recommendations to minimize importations, and close immunity gaps in communities of U.S.-residents who remain unvaccinated.