Abstract
In Germany, the childhood vaccination schedule in 2015-2020 included 13 vaccines, for which primary immunization series was recommended to be completed by 24 months of age. Childhood vaccination coverage is monitored through health insurance claims data and pre-school entry examinations. These cross-sectional systems provide limited information on individual vaccination trajectories, catch-up vaccination, and completion of the recommended vaccination schedule. We used cross-sectional (n = 2044) and longitudinal (n = 583) data from the KUNO-Kids health study (KKHS) from Regensburg, Germany (birth cohorts 2015-2020). We assessed vaccination coverage, catch-up vaccination, and completion of the entire primary immunization series according to the schedule recommended by the German Standing Committee on Vaccination (STIKO) at three follow-up time-points: 6 months, 2 years, and 4 years. Analyses included only children eligible for each assessment. At the 2-year follow-up, our cohort's vaccination coverage for all individual recommended vaccines remained below the 90-95% targets set by STIKO and the World Health Organization for 24 months of age. Vaccination coverage for all vaccines increased between the 2- and 4-year follow-up assessments for all vaccines. Coverage was lower for vaccines requiring multiple doses during the first year of life, such as the hexavalent vaccine (71-76%), than for vaccines initiated around 12 months of age and requiring fewer doses, such as MMR (86-87%). Among children with incomplete vaccination at 2 years, catch-up by 4 years was higher for MMR than for the hexavalent vaccine. Completion of the entire recommended vaccination schedule was achieved by only 50-55% of children at the 6-month and 2-year follow-ups but increased to 59-76% by the 4-year follow-up. Despite considerable catch-up before school entry, schedule adherence remained suboptimal, suggesting that vaccination schedule complexity in the first year of life may influence adherence. Interventions targeting this age group, including vaccination reminder systems and health education initiatives, should be implemented.