Prophylactic treatment with zanamivir taken once daily prevents the development
of influenza within households, a study has shown. In a double-blind, placebo
controlled study, Dr Fredrick Hayden (University of Virginia, United States)
and colleagues assessed the efficacy of prophylaxis with zanamivir in household
contacts who had been exposed to influenza.
The researchers enrolled 799 families that had between two and five members
and at least one child aged five years or older before the 1998-1999 influenza
season. Families in which one member developed influenza-like symptoms were
randomly assigned either inhaled zanamivir or placebo. The family member with
the index illness was treated with either zanamivir 10mg or placebo twice daily
for five days. Other family members received either zanamivir 10mg or placebo
once daily for 10 days, as prophylaxis.
The researchers found that zanamivir was associated with a 79 per cent rate
of protection against influenza in household contacts and that there was no
evidence of an emergence of drug-resistant viral strains. Most of the protection
of contacts was primarily because of chemoprophylaxis and not the treatment
of index cases, they say.