Does Oseltamivir Reduce Influenza Transmission?

Oseltamivir is an effective treatment for influenza, but little is known about whether it reduces infectiousness. To explore this possibility, researchers performed a secondary analysis of a community-based trial that took place in Hong Kong during the influenza seasons of 2007 and 2008, before the 2009 influenza A (H1N1) epidemic. Individuals were enrolled in the trial at the time of influenza diagnosis and were followed, along with household members, for 7 to 10 days. Decisions regarding oseltamivir use were made by the treating physician.
Of the 384 eligible study participants, 90 received oseltamivir; the rest received no antiviral therapy. Oseltamivir use was associated with a significant reduction in the time to resolution of all symptoms (P=0.01) and of respiratory symptoms (P=0.03), in particular. However, the drug was not associated with a significant reduction in the duration of viral shedding or in the likelihood that household contacts would become infected. The secondary attack rate did vary, though, according to the time of initiation of oseltamivir: 4.7% when it was initiated within 24 hours of symptom onset, 6.0% when it was initiated within 24 to 48 hours after symptom onset, and 7.0% when it was initiated >48 hours after symptom onset (P for trend<0.01).

Reference: Journal Watch Infectious Diseases (March 24, 2010)

Take home message: Oseltamivir is effective in reducing severity of influenza symptoms and shortens recovery time. However, it may not have an effect on decreasing the infectiousness unless administered early on in the course of the infection.