Pertussis epidemiology in Australia over the decade 1995-2005--trends by region and age group.

Important changes have occurred in the National Immunisation Program for pertussis during the decade 1995-2005, including the introduction of acellular pertussis vaccine for all doses, removal from the schedule of the booster dose at 18 months, and the introduction of a booster dose for adolescents. In addition, the coverage of pertussis vaccine at 12 and 24 months has substantially increased as recorded by Australian Bureau of Statistics surveys and the Australian Childhood Immunisation Register. There were 75,458 notifications nationally between 1995 and 2005, with little change in the annual number of notifications at the national level but with periodic and dramatic changes in the age distribution of notified cases. Pertussis is well controlled in the 1-4 and 5-9 year age groups, and the highest annual notification rates continue to be in infants under 6 months of age. Adolescents aged 10-19 years had high notification rates in all states and territories, over this period, but 63% of notifications are now in the 20-59 year age range. Following the introduction of a fifth dose for adolescents, the current focus should be on protecting infants too young to be vaccinated and further defining the true morbidity of the disease in the elderly population.