CLINICAL AND LABORATORY DIAGNOSIS OF PERTUSSIS IN THE REGIONS OF A LARGE VACCINE EFFICACY TRIAL IN GERMANY

As a support service for a pertussis vaccine efficacy trial, a central diagnostic laboratory was established. Physicians in the geographic a reas of the planned study were encouraged to send nasopharyngeal speci mens from children and household contacts with cough illnesses whether or not the illnesses were typical of pertussis. From April, 1991, to February, 1992, 3629 specimens were received and in 601 instances (16. 6%) Bordetella pertussis was isolated. Only 3.3% of patients with posi tive cultures had received pertussis vaccine whereas 16.1% of culture- negative patients had received vaccine (P < 0.0001). Fever was more c ommon (12.2%) in patients with negative cultures compared with those w ith positive cultures (5.4%) (P < 0.0001). B. pertussis isolation rate s fell markedly after 21 days of cough. Significantly more patients wi th negative cultures compared with those with positive cultures, had b een treated with erythromycin (8.5 vs. 2.9%; P < 0.0001). Patients wit h cough for greater than 4 weeks and specimen collection within 2 week s of cough onset had a B. pertussis isolation rate of 59%. Similarly i f whoop occurred under the same circumstances the isolation rate was 8 0%. In this study 25.5% of patients with culture confirmed pertussis h ad illnesses with cough of less than 21 days duration. This finding su ggests to us that a pertussis case definition in efficacy trials that requires cough of 21 days is excessively restrictive.