Researchers examined the common influenza season scenario of a household in which a family member is infected with influenza virus. They found that when the family member with influenza was treated with the antiviral drug oseltamivir, post-exposure oseltamivir prophylaxis of all other family members significantly reduced the frequency of virus transmission and illness in the household. Because households are important sites of influenza virus transmission, these results have implications for the management of influenza outbreaks in the community.
The prospective, open-label, randomized study was conducted in multiple centers in Europe and North America by Frederick G. Hayden, MD, of the University of Virginia and colleagues. They studied a total of 277 households with a suspected influenza introduction during the 2000-2001 season. These households had 298 ill index cases, 62% of whom were shown to be influenza-infected, and 812 contacts aged 1 year or older. In all households, the ill index member received a five-day course of oseltamivir treatment. In one-half of these households, the contacts received post-exposure prophylaxis with once daily oseltamivir for 10 days; in the other half, the household contacts received treatment only if they developed symptoms of illness. The researchers found that post-exposure prophylaxis combined with treatment of the ill household member was more effective in preventing subsequent influenza illness in contacts than treating the ill family member only. For all enrolled households, the protective efficacy of the post-exposure prophylaxis strategy was 63%, and prophylaxis reduced the number of individual contacts with laboratory-confirmed influenza illness by 73%.