Pertussis morbidity is highest in infants too young to be fully protected by routine vaccination schedules. Alternate vaccine strategies are required to maximise protection in this age-group. To understand baseline pertussis epidemiology prior to the introduction of the maternal pertussis vaccination program in 2014, we conducted a retrospective case series analyses of 53 901 notifications and temporal trends from 1997 to 2014. Notifications were highest in infants younger than 4 months of age and highest annual notification rates in infants younger than 1 month of age (308/100 000 per year). Amongst Aboriginal and Torres Strait Islander infants aged younger than 1 month, this rate was 576/100 000 per year. Notification rates were 40% higher amongst women 15-44 years, 62·4/100 000 population compared with men (44·5/100 000) and 90% higher in Aboriginal and Torres Strait Islander women of the same age (38·2/100 000) compared with men (19·7/100 000). Six infant deaths were identified, all younger than 2 months of age. Monitoring epidemiology in at-risk groups - infants too young to be vaccinated, women of childbearing age and Aboriginal and Torres Strait Islander peoples - following implementation of the maternal pertussis vaccination program will be important to assess its impact and safety.
Keywords: Baseline; epidemiology; maternal vaccination program; notifications; pertussis.