Inclusion Criteria:  Cases were included if they met the following inclusion criteria:  Reported pertussis disease in the referenced EIP surveillance database Age greater than 2 days and younger than two months of age Resided in the catchment area on date of onset of their cough Born in a hospital in their state of residence ≥ 37 weeks of gestation at birth Not adopted, in foster care or living in a residential care facility Completed maternal interview Completed infant and maternal information  Controls were included if they met the following inclusion criteria:  Age greater than 2 days and younger than 2 months of age on date of cough onset for the corresponding case infant Resided in the catchment area on date of cough onset for the corresponding case infant Born in a hospital in their state of residence ≥ 37 weeks of gestation at birth Not adopted, in foster care or living in a residential care facility Maternal interview completed Infant and maternal information complete  Exclusion Criteria:  Cases were excluded if they met any of the following exclusion criteria:  Vaccination status of the mother unknown Infants whose mothers were vaccinated with Boostrix or an unknown vaccine brand  Controls were excluded if they met any of the following exclusion criteria:  Vaccination status of the mother unknown A pertussis diagnosis prior to the cough onset date of the corresponding case infant Controls that were matched to Boostrix or an unknown brand cases