This is a nationwide population-based register study on pertussis in children less than 14 years of age in 1995-2019. We will estimate the effectiveness of preschool pertussis vaccination in a cohort design, by previos vaccination status and by time since vaccination, and assess its impact by comparing vaccination programs with and without preschool vaccination. In addition, we will assess the patterns of pertussis by age, time, area, vaccination status and hospitalization.
