Characterizing measles healthcare facility exposures-December 2023-September 2025-New York City.

BACKGROUND: When people develop measles (cases), healthcare facility exposures are common and result in many potentially exposed people requiring resource-intensive control measures. We summarized exposures and transmission among people exposed to measles (contacts) in healthcare settings in New York City (NYC). METHODS: NYC Health Department's surveillance data of NYC contacts exposed to measles cases in any NYC healthcare facility during December 2023-September 2025 was analyzed as a retrospective descriptive study. Characteristics summarized included measles transmission, immunity status, post-exposure prophylaxis (PEP) administration, facility setting, and time of measles exposure. RESULTS: Of 2,122 healthcare contacts to 28 cases, no secondary cases occurred. 1,285 (60.6%) were vaccinated or had other evidence of immunity, 618 (29.1%) were adults with unknown immunity, 124 (5.8%) were not immune and received PEP, and 95 (4.5%) were not immune and did not receive PEP. Most contacts were exposed in emergency departments and/or hospital inpatient settings (1,406; 66.3%). Among 1,028 contacts with known time of exposure (48.4% of all contacts), 785 (76.4%) overlapped with the case in the healthcare facility, 146 (14.2%) arrived within 1 hour and 97 (9.4%) arrived 1-2 hours after the case left or was isolated. CONCLUSIONS: Most contacts exposed to measles in NYC healthcare facilities had presumptive immunity or were adults with unknown immunity. No transmission occurred among 2,122 exposed contacts, including non-immune contacts. Given no secondary transmission and resource-intensive control measures, relying solely on time-based measles exposure definitions may be overly broad. Incorporating strategies like facility air exchange data might better assess transmission risk.