Examining the 2018-19 New York State Measles Outbreaks

2019 has been a historic year for measles in the United States. The nation has been experiencing one of the largest and longest outbreaks of the disease since it was eliminated in 2000. As of September 19, there have been 1241 cases confirmed nationwide. Most of the cases in the nation have occurred in the state of New York in pockets of unvaccinated communities.

In a late breaking oral abstract session at IDWeek 2019, health officials presented 2 oral abstracts focusing on the New York measles outbreaks.

The first presentation covered cases of measles in outbreaks in the state of New York with the exception of cases in New York City. The investigators used CSTE measles case definition and either laboratory confirmation or direct epidemiologic linkage to identify cases. There were 371 cases reported between October 1, 2018 through July 25, 2019.

The health officials obtained demographic and clinical characteristics for each confirmed case. Additionally, medical record reviews were completed for individuals who had an encounter at a hospital, emergency department, or urgent care center.

Of the 371 cases, 283 occurred in Rockland County, 55 in Orange County, 18 in Westchester County, 14 in Sullivan County, 1 in Greene County. Eleven cases were imported from international travel.

Overall, the median age of affected individuals was 5.5 years and 79% of these cases occurred in children under 18 years of age. Furthermore, 79% of the cases did not receive any doses of the measles, mumps rubella vaccine (79%). More specifically 71% of the children did not receive a single dose of the vaccine, and 83% of the children were over the age of 1 year.

While there were no deaths or documented cases of encephalitis, 28 (8%) patients were diagnosed with pneumonia and 25 (7%) patients were hospitalized. Of the 17 hospitalized children, 5 (29%) were admitted to the intensive care unit (ICU). Two preterm births occurred at 34 and 25 weeks gestation to women with measles while pregnant. Between October 2018 and July 2019, providers in outbreak counties vaccinated 72,465 individuals with the MMR vaccine, representing a 46% increase from the same period the year prior.

“Unvaccinated children were identified as the largest group affected and experienced severe complications; nearly 30% of hospitalized children were admitted to an ICU,” the authors of the abstract concluded. “These data support the critical need for continued education and outreach on the risks of measles and the value of vaccination to prevent continued circulation in undervaccinated communities and potential further cases of severe disease.”

The second abstract featured an evaluation describing adult measles cases in the measles outbreak in New York. The evaluation included all confirmed cases in individuals 18 years and older excluding New York City residents October 1, 2018—July 25, 2019.

There were 79 cases of measles in adults during this time period. Four cases occurred in individuals born before 1957, 3 of whom were unvaccinated and 1 with unknown vaccine status. Among the 75 cases born during or after 1957, 65 (87%) were unvaccinated or had unknown vaccine status, while 3 individuals had one dose and 7 individuals had 2 doses of the MMR vaccine.

Notably, 5 of the 11 internationally imported measles cases were documented in adults, and all were unvaccinated or had unknown vaccine status. During the first month of the outbreak, 51% cases were attributable to adults; of the 26, 15 (58%) of cases occurred in adults and 11 (42%) were in children who acquired infection from adults.

According to the authors of the abstract, measles cases in unvaccinated adults played a critical role in importing the disease and transmitting measles in the early stages of the outbreak.

“These data strongly support current recommendations of 1 dose of measles, mumps, rubella vaccine (MMR) for most adults and 2 doses of MMR for adults traveling internationally and at high-risk such as those in outbreak areas, as determined by local/state public health,” the authors conclude.

The abstracts, Measles Outbreak in New York State (NYS) outside of New York City, 2018-2019, and The Role of Adults in the Measles Outbreak in New York State outside of New York City, 2018—2019, were presented in a late breaker session on Saturday, October 5, 2019, at IDWeek 2019 in Washington DC.