National and regional variations in timely adherence to recommended measles vaccination scheme in 2-years old in Switzerland, 2005–2019

BACKGROUND Although monitoring of vaccination program performance is usually evaluated by measurement of vaccine coverage, timely uptake is rarely part of this assessment. This study aims to examine the timeliness of the administration of a measles-containing-vaccine (MCV) for 2-year-old children between 2005 and 2019. METHODS We used data from the Swiss National Vaccination Coverage Survey 2005-2019 for the study. We defined timely vaccinated as a vaccination administered within the recommended age specified in the Swiss National Vaccination Schedule, with an added tolerance period of 30.4 days for both MCV 1 and 2 doses. The median delay time was estimated by Kaplan-Meier survival curve and examined using log-rank test. A Cox hazard ratio was used to identify factors associated with delay. RESULTS 81% (95% CI:79-82%) of toddlers were timely vaccinated for MCV1 and 82% (95% CI:81-83%) for MCV2 in survey period 2017-2019. Between 2005 and 2019, the median age of vaccinated children ranged between 12.2 and 12.5 and 18.3-22.0 months for MCV1 and MCV2 with median delay of 44 and 38 days, respectively, at the national level. Children in the French-, Italian- and German-speaking regions were vaccinated earlier between 2005 and 2019 for MCV1 (vaccination coverage range before 10 months of age: 1.7-45.9%, 1.2-35.3% and 1.4-15.0%, respectively). Nationality, linguistic regions, and survey periods were the strongest predictive factors related to prolonged delay time. CONCLUSION Overall adherence to recommendations has improved over time, as MCV coverage has significantly increased over the years with differences across linguistic regions. Vaccinations were administered earlier and with shorter delay time