Pertussis epidemiology prior to the introduction of a maternal vaccination program, Queensland Australia.

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.