2013 New York measles outbreak reached 58 cases

VANCOUVER, British Columbia — In 2013, 58 cases of measles occurred in New York City among residents of two Orthodox Jewish Communities, according to a presentation at the 2014 Pediatric Academic Societies Annual Meeting.

“This was the largest single outbreak of measles in the United States since 1996 and the largest number of cases we’ve had in New York City since 1992,” Jennifer B. Rosen, MD, of epidemiology and surveillance, Bureau of Immunization, at New York City Department of Health and Mental Hygiene, said during the presentation.

However, this outbreak was surpassed during the first 4 months of this year, with 129 documented measles cases.

The 2013 outbreak began with a 17-year-old male who had been studying in London and returned to Borough Park, Brooklyn, in March while still infectious. The patient was part of a large extended family of people who had refused vaccination, which allowed measles to spread to several family members and subsequently 28 neighbors in the community as well as members of Williamsburg, a neighboring Orthodox Jewish Community.

The first measles case in Williamsburg occurred in April in a relative of one of the Borough Park measles cases. Measles eventually spread to 30 people throughout this community with the last case reported in June.

“None of the cases in this outbreak had documentation of having been vaccinated at the time that they were presumed to have been exposed to measles,” Rosen said. “In Borough Park, where the outbreak first occurred, 18% of the cases were less than 1 years of age, so too young to have been vaccinated.”

Seventy-nine percent of the patients with measles in Borough Park were aged 12 months or older and most were part of three large extended families who had refused vaccination.

Once measles spread to Williamsburg, 23% of the cases were among children aged younger than than 1 year and 30% were aged 12 months and older whose families refused vaccine; however, 27% of cases were from families who delayed vaccination.

“We saw a really interesting change in the age distribution from the start to the end of the outbreak,” Rosen said. “In March, the median age of cases was 17 years and that’s consistent with the population that had been refusing vaccination, but by the end of the outbreak the median age went to 17 months. This was consistent with a shift toward babies who were too young to be vaccinated and parents who delayed but didn’t refuse vaccination.”

Half of the cases acquired measles infection from a relative and other sources, including residents in the same building, through a friend or a playmate, or nosocomial transmission in the health care setting.

Thirty-one percent of the cases never actually presented for medical care and were only identified through interviews of secondary cases. Also, 9% of cases saw a health care provider but were not reported to the health department at the time the measles diagnosis was first considered.

“Over 3,500 exposed contacts were identified during this outbreak,” Rosen said.

The health department recommended home isolation or post-exposure prophylaxis for exposed contacts that were susceptible to measles. Recall letters were sent to families of children who were not up-to-date with measles-mumps-rubella vaccine (MMR; M-M-R II, Merck) in the affected communities and rapid distribution of vaccines was provided to health care providers.

The health department also recommended that pregnant women have their immune globulin G titers checked and that pregnant women should be vaccinated with MMR post-partum if needed.

“Even though this is not a standard recommendation, we did this during the outbreak because of both the shift toward the younger age of cases being affected and because in this community, women are frequently pregnant,” Rosen said. “There were very large household sizes.”

Although these were religious communities, which typically have lower rates of school-mandated immunizations, the health department found that 95% of students in the religious schools were up-to-date with immunizations.

During the outbreak, the health department recommended that MMR vaccine be given to infants aged 6 to 11 months. However, the dose was not counted as valid and needed to be repeated at aged 1 year. A second dose of MMR was also recommended to be given earlier than aged 4 years as long as 28 days had passed since the first dose.

“The outbreak really began as a results of a small number of families who had decline vaccination that later spread to infants who were too young to be vaccinated and children whose vaccinations were delayed,” Rosen said. “However, high population MMR coverage really limited spread both within and beyond the community. While 58 cases is a low number of cases of measles in the post-elimination era, had vaccination coverage not been so high, we would have expected to see thousands of cases, similar to what was seen before the vaccine was introduced.” — by Amber Cox

For more information:

Rosen JB. Abstract 2323A.5. Presented at: May 2-6, 2014; Vancouver, British Columbia.

Disclosure: Rosen reports no relevant financial disclosures.