TABLE 2 Number of Cough Episodes and Laboratory-Confirmed Infections, by Hierarchic Diagnostic Laboratory Criteria and by Vaccine Received Vaccine Received Total DTaP SB DTaP CB DT Cough episodes 830 781 342 1953 Laboratory-investigated (%) 94% 93% 95% 93% Laboratory-confirmed B pertussis infections 138 (100%) 126 (100%) 127 (100%) 391 (100%)   Culture-confirmed 35 (25.3%) 30 (23.8%) 57 (44.9%) 122 (31.2%)   Increase in antibody titers 50 (36.2%) 57 (45.4%) 56 (44.1%) 163 (41.7%)   Single IgG PT titer 53 (38.4%) 39 (30.9%) 14 (11.0%) 106 (27.1%)