Measles is a rash illness that can cause complications and death. Before the measles vaccine, an estimated 3-4 million cases, 48,000 hospitalizations, and 450 measles deaths occurred annually in the U.S. Measles was declared eliminated from the U.S. in 2000. Since the last published summary of measles epidemiology in the U.S. was during 2001-2008, we summarized U.S. measles epidemiology during 2009-2014.
We analyzed demographic, vaccination, and virologic data on confirmed measles cases reported to the Centers for Disease Control and Prevention from January 1, 2009 through December 31, 2014. Vaccine coverage data were from the National Immunization Survey.
From 2009-2014, 1265 confirmed measles cases were reported in the U.S. The annual median of 130 cases (range: 55-668 cases) was more than double the annual median of 56 cases from 2001-2008. Among U.S.-resident case-patients, children aged 12-15 months had the highest measles incidence (65 cases, or 8.3 cases/1 million person-years), and infants aged 6-11 months had the second highest incidence (86 cases, or 7.3 cases/1 million person-years). From 2009-2013, one-dose measles-mumps-rubella (MMR) vaccination coverage among children aged 19–35 months was 90%-92% and 2-dose coverage among adolescents was 89%-92%. During 2009-2014, 879 (75%) of 1174 U.S.-resident case-patients were unvaccinated and 171 (15%) had unknown vaccination status. Of 914 vaccine-eligible U.S.-resident case-patients, 646 (71%) claimed a personal belief exemption. During 2009-2014, 272 (22%) cases were imported from 58 countries. Measles genotypes B3, D4, D8, D9, G3, and H1 were detected during this time.
Although the U.S. has maintained measles elimination, imported cases still occur. Infants and young children remain the most highly affected groups. More than two-thirds of cases occurred among unvaccinated individuals; a majority claimed personal belief exemptions. Since measles outbreaks continue to occur globally, the U.S. remains at risk of imported measles and potential spread. To maintain elimination, it will be necessary to maintain high two-dose vaccination coverage, continue case-based surveillance, and monitor the patterns and rates of vaccine exemption.
A. P. Fiebelkorn,
P. Gastanaduy, None
N. Clemmons, None
P. Rota, None
J. S. Rota, None
W. J. Bellini, None
G. S. Wallace, None