Transmission Dynamics of and Insights from the 2018-2019 Measles Outbreak in New York City: A Modeling Study

In 2018-2019, New York City experienced the largest measles outbreak in the US in nearly three decades. To identify key factors contributing to this outbreak to aid future public health interventions, here we developed a model-inference system to infer the transmission dynamics of measles in the affected community, based on incidence data. Our results indicate that delayed vaccination of young children aged 1-4 years enabled the initial spread of measles and that increased infectious contact among this age group, likely via gatherings intended to expose unvaccinated children (i.e. “measles parties”), further aggravated the outbreak and led to widespread of measles beyond this age group. We found that around half of infants were susceptible to measles by age 1 (the age-limit to receive the first vaccine dose in the US); as such, infants experienced a large number of infections during the outbreak. We showed that without the implemented vaccination campaigns, the outbreak severity including numbers of infections and hospitalizations would be 10 times higher and predominantly affect infants and children under 4. These results suggest that recommending the first vaccine dose before age 1 and the second dose before age 4 could allow pro-vaccine parents to vaccinate and protect infants and young children more effectively, should high level of vaccine hesitancy persist. In addition, enhanced public health education is needed to reduce activities that unnecessarily expose children to measles and other infections.