Seroepidemiology of whooping cough in the Czech Republic: estimates of incidence of infection in adults.

OBJECTIVES: Despite widespread vaccination programmes, pertussis remains a significant health burden in many countries. Low awareness of the disease, the high rate of asymptomatic cases in adults and difficulties with diagnosis could explain the under-reporting of pertussis. The lack of data on actual incidence constitutes an obstacle for public health authorities for the implementation of a vaccination strategy against pertussis in adults. The aim of this study was to evaluate the seroprevalence of antibodies against Bordetella pertussis infection in adults and to estimate the actual incidence of the disease compared with the reported incidence.

STUDY DESIGN: Prospective, multicentre seroprevalence study.

METHODS: The study was conducted in 2000 adult subjects aged ≥18 years who had not received pertussis vaccination within the last 5 years. All enrolled subjects provided a blood sample for serum testing of IgG antibodies against pertussis toxin, performed by enzyme-linked immunosorbent assay, to indicate if they had an acute infection or if they had been infected with pertussis within the last 12 months or earlier. Results were validated in accordance with the guidelines of the European Sero-epidemiology Network 2 and were expressed in ESEN units/ml.

RESULTS: A positive concentration of anti-pertussis toxin antibodies, indicating previous pertussis infection, was demonstrated in 39.9% (n = 799) of all study subjects, and 0.40% (n = 8) of subjects had a concentration suggestive of a recent infection (within the last 12 months). The highest antibody seroprevalence was observed in subjects aged 18-29 years (1.46%). No cases of acute infection were detected.

CONCLUSIONS: During the study period, the reported incidence of pertussis in the adult population was 0.84/100,000 inhabitants. Based on the seroprevalence results from this study, it is estimated that the actual incidence of pertussis could be as much as 699/100,000 inhabitants. The actual incidence of pertussis in adults in the Czech Republic could therefore be at least 200-fold higher than the reported incidence. These findings support the need for pertussis vaccination in the adult population.