Impact of a Pertussis Booster Vaccination Program in Adolescents and Adults on the Epidemiology of Pertussis in Austria

Abstract

A resurgence of pertussis has been observed in several countries; however, inconsistent data are available for Europe. In Austria, routine pertussis vaccination for babies is administered at 3, 4, and 5 months, and in the second year of life. Since 2002, regular boosters for all persons >6 years of age (including adults) are recommended. This study was undertaken to analyze epidemiologic trends of laboratory-reported pertussis to evaluate current vaccination strategy in Austria. Epidemiologic surveillance of laboratory-reported pertussis was conducted from January 1, 2000, to December 31, 2005. Infection was confirmed by positive serology, by positive culture of Bordetella pertussis, or by detection of sequences of the pertussis toxin gene by real-time polymerase chain reaction (RT-PCR). Data were assessed by age, hospitalization rate, seasonality, and incidence rate. During the observation period 4395 reported cases of pertussis were eligible for analysis. The mean annual incidence increased from 6.4 per 100,000 population in 2000 to 11.1 cases per 100,000 population in 2005. Incidence rates were highest among children less than 1 year of age. Decreasing rates were observed for children and adolescents <16 years of age, whereas increasing rates were detected for persons 16 years of age and older. The mean age of reported pertussis cases increased from 30 years (+/-25.9 SD) in 2000 to approximately 44 years (+/-23.7 SD) in 2005. Hospitalization rates were highest in infants <6 months (86%) and lowest in those 10 to <50 years of age (17%), followed by an increase to 80% in persons 85 years of age and older. In general, no seasonal occurrence of disease was apparent. Pertussis incidence remains high among adults implying that coverage rates regarding booster vaccinations for adolescents and adults still are too low. Reinforced application of the current booster strategy is needed.