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.
S. Omer, None