1866. Estimating the Number of Measles-susceptible Children in the United States Using the NIS-Teen
Session: Poster Abstract Session: Vaccines: Improving Immunization Uptake
Saturday, October 10, 2015
Room: Poster Hall
Background: Despite high measles vaccination rates in the United States, imported measles cases have led to outbreaks in the United States. While there have been a number of these outbreaks in recent years, they have not led to sustained measles transmission. In addition to children not vaccinated against measles, some children and adolescents are not vaccinated until older ages, leaving them vulnerable until they are vaccinated. With each birth cohort of children not fully vaccinated against measles, there is an accumulation of measles-susceptible individuals in the population. The total number of these accumulated measles-susceptible individuals, and the proportion of the population they contribute relative to the herd immunity threshold, is unknown. 

Methods: We used age-specific measles vaccination data, for doses 1 and 2 of measles-containing vaccine, from the National Immunization Survey-Teen to estimate the number of measles-susceptible children and adolescents, aged 17 and younger. Our estimates of measles susceptibility also accounted for vaccine effectiveness, infant protection from maternal antibodies, and loss of immunity following childhood cancer treatment. 

Results: Approximately 12.5% of children and adolescents in the US are susceptible to measles, with the highest levels of susceptibility observed in children three years and younger (24.7% susceptible to measles). In sensitivity analyses varying vaccine coverage estimates, a sustained decrease in measles vaccination coverage levels to 98% of current coverage over multiple birth cohorts would add nearly 1.2 million susceptible children and adolescents (14.2% of those 17 years and younger susceptible to measles). In this scenario, no age group would reach the 92% herd immunity threshold. 

Conclusion: This analysis highlights the need for high measles vaccination coverage to support population-level immunity and prevent reestablishment of indigenous measles transmission in the United States.

Robert Bednarczyk, PhD, Departments of Global Health and Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, Walter A. Orenstein, MD, FIDSA, FPIDS, Medicine, Emory University, Atlanta, GA and Saad Omer, MBBS, MPH, PhD, FIDSA, Emory Vaccine Center, Atlanta, GA

Disclosures:

R. Bednarczyk, None

W. A. Orenstein, None

S. Omer, None

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