Outbreak of Haemophilus influenzae type b disease among fully vaccinated children in a day-care center

Background. Two cases of invasive Haemophilus influenzae type b (Hib) infection were reported in immunized children in a day nursery within 1 week. Both cases were younger than 18 months of age, cared for in the same room. We aimed to characterize carriage of Hib and response to eradication therapy in this setting. Methods. Ninety-four children were enrolled in the nursery, cared for by 21 staff in 4 rooms, divided by age. Two children of a part time teacher also attended. Oropharyngeal swabs were taken to detect Hib carriage before introduction of rifampin prophylaxis (20 mg/kg/day for 4 days). A questionnaire addressing risk factors for colonization was administered to parents and staff. Carriage was reassessed in children and carers from the same room as the index cases 1 month later. Results. Eighty-nine children and all 21 staff were swabbed. Two additional Hib carriers, 1 child and 1 staff member, were identified from the same room as the cases. These isolates appeared identical with those causing invasive disease. Given the small numbers no clear risk factors for carriage could be confirmed. Compliance with rifampin prophylaxis was 97.4%. One month later no carriers were found among the 7 children and 3 staff tested from the room in which the cases were originally identified. Conclusions. Although immunization against Hib has resulted in a reduction in the incidence of this disease in the UK, individual protection cannot be assumed to be infallible. The importance of timely chemoprophylaxis of close contacts of a child with invasive Hib disease is reinforced.