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By Stan Deresinski, MD, FACP, FIDSA
Clinical Professor of Medicine, Stanford University, Editor of Infectious Disease Alert
SYNOPSIS: The combination of global travel and resistance to vaccination has led to a resurgence of measles cases in the U.S.
SOURCE: Gastañaduy PA, et al. Measles United States, January 1-May 23, 2014. MMWR 2014;63:1-4.
Measles was declared to have been eliminated in the U.S. in 2000. However, the infection is endemic in 5 of the 6 World Health Organization regions of the world and causes an estimated 20 million cases in the world each year. At the same time in the U.S. (and elsewhere), increasing numbers of parents are refusing to vaccinate their children. Thus, it perhaps should not be surprising that the CDC now reports that the 288 reported confirmed cases of measles in the first 143 days of 2014 is greater than the reported total yearly total cases for each year since 2000.
Fifteen outbreaks accounted for approximately four-fifths of cases, including one involving 138 cases, which had not ended at the time of this report. Cases were reported from 18 states and New York City and included 138 cases in Ohio (introduced by Amish missionaries returning from the Philippines), 60 in California, and 26 in New York City. Infections were associated with importation from a total of 18 countries in 97% of cases; the source could not be determined for the remaining in 3%. These included 45 direct importations by 40 U.S. residents and 5 foreign visitors. The 40 U.S. travelers were unvaccinated, and 22 acquired measles in the Philippines, where 32,030 measles cases (26,014 suspected cases and 6,016 confirmed cases) and 41 measles deaths have been reported from January 1 through April 20.
Only 30 (10%) of cases occurred in individuals who were known to have been vaccinated, while unvaccinated individuals accounted for 200 (69%) of cases and 58 (20%) had an unknown vaccination status. More than half the cases occurred in 3 outbreaks that resulted from introduction of a case into groups that remained unvaccinated because of philosophical or religious beliefs. Overall, such beliefs or unspecified personal objections accounted for 85% of those who were unvaccinated, while missed vaccination opportunities and being too young for vaccination accounted for 6% and 5%, respectively.
The age of those affected ranged from 2 weeks to 65 years, with 6% being <12 months. Those ages 1-4 years accounted for 17% of cases, while 25% were in individuals 5-19 years and 52% were >20 years. Fifteen percent were hospitalized. While there were no deaths and no cases of encephalitis, 5 patients developed pneumonia and one each had hepatitis, pancytopenia, and thrombocytopenia.
In the U.S., MMR vaccination is recommended for all children, with the first dose given at 12-15 months and a second dose at 4-6 years, with catch-up vaccination for older children and adolescents who did not adhere to this schedule. In the absence of other evidence of immunity, adults should receive at least one dose of MMR while 2 appropriately spaced doses are recommended for healthcare personnel, college students, and international travelers. One dose of MMR vaccine is recommended for infants 6-11 months of age prior to travel, while 2 doses given at least 28 days apart are recommended for those >12 months.
The increase in measles cases in the U.S. is the result of a confluence of globalization and vaccine denial. The former cannot be avoided, but improved vaccination strategies as applied to international travelers is clearly indicated. Solving the problem presented by individuals and groups opposed to vaccination is much more difficult.