Lay summary
In a recent study (PIPIO Study), we found that infants born to mothers given the whooping cough vaccine in pregnancy, were at greater risk of whooping cough in the period following their own first dose of vaccine (at 6 weeks of age) than infants born to unvaccinated mothers. Despite the importance of these findings, the sample size was small and the results need testing against a larger cohort. The proposed research will use data from all births from 2013 to 2017, identify all infants in this group diagnosed with whooping cough and determine whether or not their mothers received the vaccine in pregnancy. The research findings will inform the NZ immunisation schedule and the current strategy of commencing infant vaccination at 6-weeks of age rather than 8-weeks as is practiced in most other high-income countries.