RESUMEN
BACKGROUND AND OBJECTIVES: Pertussis remains an important cause of morbimortality despite current vaccination strategies. This study was designed to describe the results and characteristics of close contacts of pertussis cases diagnosed in children less than 16 years in a tertiary hospital in Barcelona. PATIENTS AND METHODS: Cross-sectional study. Data were collected from chart review of contacts of paediatric cases of pertussis in Vall d'Hebron University Hospital from 2005 to 2009. Only patients with microbiological study done were included. The odds ratio (OR) and 95% confidence interval (95% CI) were calculated as association measure. RESULTS: Ninety-one index cases and 404 contacts were studied. The prevalence of positive cases among contacts was 33.2%. Contacts of index cases younger than 6 months had a higher risk of being positive for pertussis than contacts of older children (OR: 3.38; 95% CI: 1.88-6.10). Primary cases were identified as 16.7% of the contacts studied, who were the source of infection for 67.7% of index cases younger than 6 months and for 26.9% of older index cases. CONCLUSIONS: Contact tracing of paediatric pertussis cases is a necessary clinical activity. It is more likely to find primary cases in the contact investigation of children less than 6 months. Preventive strategies should be targeted primarily to frequent contacts of this age group.