Effect of post-exposure prophylaxis with oseltamivir for those in contacts with influenza patients in pediatric wards

During the influenza season, outbreaks of influenza may occur in the pediatric wards due to spread from the patients hospitalized with influenza, or from those hospitalized during the latency period and develop influenza afterwards. Post-exposure prophylaxis with neuraminidase inhibitors has been reported to be effective in preventing outbreaks among household members and nursing home residents. However, for nosocomial spread, its effectiveness and possible adverse effects are to be determined. During the 2002/2003 influenza season, we experienced a total of 3 nosocomial outbreaks of influenza in the pediatric wards in two hospitals in the Kanto district, Japan. Since the number of contacts who developed influenza had been increasing despite the isolation precaution implemented, post-exposure prophylaxis with oseltamivir (2 mg/kg/dose, maximum 75 mg/dose, once a day for 7-10 days) was implemented with a permission from the parents to terminate the outbreaks. In the outbreaks (one with influenza A, two with influenza B), a total of 29 inpatients had contact with influenza patients: among those 29, 13 were given post-exposure prophylaxis, 16 were not. Out of 16 patients who did not receive post-exposure prophylaxis, 11 (69%) developed influenza: out of 13 with post-exposure prophylaxis, none developed influenza. Those patients who developed influenza were given oseltamivir (2 mg/kg/dose, maximum 75 mg/dose, twice a day for 5 days) and accommodated in a private room or a room with other patients with influenza of the same type. No significant adverse effects due to oseltamivir were observed among those who were enrolled in this study.