Measles clinical presentation, hospitalization and vaccination status among children in a community-wide outbreak.

Background: In 2018-2019, a measles outbreak emerged in Israel (4158 notified cases). We aimed to evaluate the measles characteristics and the vaccination status among children during the outbreak.

Methods: We performed a cross-sectional study of measles cases in children under 18 years, residing in the Jerusalem district (2254 notified measles cases, June 2018-May 2019). The variables included: clinical symptoms (fever, rash, cough, coryza, conjunctivitis), hospitalizations and child's vaccination status. The national measles vaccination schedule includes two vaccine doses (at ages 12 months and 6 years).

Results: Children, under 18 years, comprised 79% (1782/2254) of the notified measles cases. The hospitalization rate was 6.6%. There was one fatality. The measles vaccination status was analyzed by age groups. Infants under 12 months (n = 425) were excluded. Children aged 1-5 years (n = 785) and 6-17 years (n = 572) were expected to receive 1 and 2 measles vaccine doses, respectively. Most (88%) children (1-17 years) were unvaccinated, 138 received 1 measles vaccine dose and 24 received 2 doses. Of children aged 1-5 years 106 (13.5%) received 1 vaccine dose and were compared to unvaccinated children. Vaccinated children showed lower rates of clinical symptoms and lower risk for hospitalization compared to unvaccinated children (Odds ratio: OR = 4.8, 95%CI 1.12-20.2). Vaccine effectiveness of 79% was estimated for one measles vaccine dose against hospitalization.

Conclusions: Data on vaccine effectiveness reflect how well vaccines protect children against infection and morbidity. We evaluated the real-world effectiveness of measles vaccine, in an outbreak setting, and showed reduced morbidity in once-vaccinated children.