Survey of Japanese infants younger than 3 months who were treated with oseltamivir for influenza: safety of oseltamivir treatment.

BACKGROUND: Young infants with influenza virus infection are frequently hospitalized, and are at risk of serious complications including death. With the emergence of pandemic influenza A/H1N1 2009, oseltamivir was approved for use in Europe and the USA, including use in infants aged < 3 months. However, few data are available regarding the safety of oseltamivir treatment for influenza in infants aged < 3 months. METHODS: The clinical data from Japanese infants aged < 3 months with laboratory-confirmed influenza virus infections, who were treated with oseltamivir between October 2009 and April 2011, were collected and analyzed. RESULTS: Forty-four infants were included in the study. The median age was 1 month (range 4 days to 2 months) and median body weight was 4.5 kg (range 2.6-7.6 kg). Thirty-eight infants (86%) had no underlying diseases. The most common presenting symptom was fever (42 infants, 95%). There were no cases of influenza-associated encephalopathy or myocarditis. The median time between the onset of influenza symptoms and initiation of oseltamivir treatment was 0 days (range 0-7 days), with treatment initiated within 1 day in 40 infants (91%). The oseltamivir dose was 1.5-2 mg/kg twice daily in 98% of infants. No serious adverse events were identified during treatment. All infants recovered completely. CONCLUSIONS: Treatment of influenza with oseltamivir 1.5-2 mg/kg twice daily may be safe in infants aged < 3 months.