[Effect of vaccination against pertussis on the incidence of pertussis in The Netherlands, 1996-2003].

Objective: To determine whether booster vaccination of 4-year-old children with an acellular pertussis vaccine, which has been included in the national vaccination programme since October 2001, has decreased the incidence of pertussis.

Design: Descriptive.

Methods: Surveillance data were studied: mandatory notifications to the Health Inspectorate and reports of hospital admissions from the National Medical Register.

Results: During the past 7 years, there has been an increase in the incidence of pertussis every 2-3 years (1996, 1999, 2001). Moreover, the annual incidence in 1996-2003 was higher than in 1989-1995. As in previous years, the yearly peak incidence for hospital admissions due to pertussis was observed among nurslings, especially those younger than 3 months of age. In 2002 compared to 2000, the incidence among 3-4-year-olds on the basis of notifications and hospitalisations was 45% and 62% lower, respectively, very likely due to the booster vaccination for 4-year-olds introduced in 2001. The greatest decrease in the incidence was also observed among the 4-year-olds in 2003.

Conclusion: Pertussis is still endemic in The Netherlands with a higher incidence than before the epidemic of 1996-1997. Severe disease often occurs, especially among unvaccinated children < 1 year of age. From January 2005 onwards, the vaccinations in the first year of life have been given with an acellular pertussis vaccine. However, since such infants are too young to be protected by vaccination alone, more information is needed on the most important sources of infection of nurslings in The Netherlands.