The incidence of Bordetella pertussis infections estimated in the population from a combination of serological surveys.
OBJECTIVE
Bordetella pertussis circulates even in highly vaccinated populations. There is a considerable amount of infection in adults. For designing more effective vaccination schedules it is important to quantify the age-dependent relation between the number of notified cases and the number of infections.


METHODS
We used a statistical relationship between the time since infection and the IgG antibody titers against pertussis toxin, derived from a longitudinal data set, to estimate time since infection for all individuals in a cross-sectional population-based study (1995-1996) based on their titers. Age-specific incidence of infection with B. pertussis was calculated and compared with the age-distribution of notified cases of pertussis in 1994-1996.


RESULTS
Estimated incidence of infection was 6.6% per year for 3-79-year olds, annual incidence of notified cases 0.01%. Estimated age-specific incidence of infection was lowest for 3-4-year olds (3.3%) and increased gradually up to the age of 20-24 years (10.8%). The number of notified cases was highest for 3-9-year olds.


CONCLUSIONS
In the Dutch population B. pertussis infections occur more frequently and in elder age-categories then suggested by notifications. Mathematical modeling could explore what booster vaccination strategies are most effective in reducing severe disease among not (completely) vaccinated infants.
de Melker
Hester E
HE
Department of Infectious Diseases Epidemiology, National Institute of Public Health and the Environment, Bilthoven, The Netherlands.
Versteegh
Florens G A
FG
Schellekens
Joop F P
JF
Teunis
Peter F M
PF
Kretzschmar
Mirjam
M
D000293:Adolescent; D000328:Adult; D000375:Aging; D000907:Antibodies, Bacterial / Q000097:blood; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D015994:Incidence; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D016036:Seroepidemiologic Studies; D014917:Whooping Cough / Q000453:epidemiology*
D000907:Antibodies, Bacterial; D007074:Immunoglobulin G