Timing of measles immunization and effective population vaccine coverage.

OBJECTIVE To describe measles vaccination patterns in a cohort of Swiss children aged up to 3 years insured with a single health insurer. METHODS A dynamic cohort study evaluating measles immunizations patterns in children born between 2006 and 2008 was conducted. Time-to-event analysis was used to describe timing of measles immunization. Effective vaccine coverage was calculated by using an area under the curve approach. RESULTS In the study cohort, 62.6% of 13-month-old children were up-to-date for the first measles immunization (recommended at 12 months of age). Approximately 59% of 25-month-old children were up-to-date for the second measles immunization (recommended at 15-24 months of age). Most doses were delivered during months in a child's life when well-child visits are recommended (eg, 12 months of age). For second measles vaccine dose, accelerations in vaccine delivery occurred at time points for well-child visits during the months 19 and 25 of age but with lower final uptake than for the first measles vaccine dose. Until their second birthday, children in our cohort spent on average 177 days and 89 days susceptible to measles due to policy recommendations and additional delays, respectively. In a group of children aged 6 months to 2 years reflecting the age distribution in our cohort, effective vaccine coverage was only 48.6%. CONCLUSIONS Timing and timeliness of measles immunizations influence effective population vaccine coverage and should be routinely reported in addition to coverage whenever possible. Proposed timing and relation of recommended vaccinations to well-child visits could be relevant aspects in optimizing measles vaccine coverage to reach measles elimination.