Rimantadine prophylaxis in children: a follow-up study.

In a randomized, double-blind placebo-controlled clinical trial, we evaluated the prophylactic effectiveness of rimantadine in children (ages 1 to 18 years) against infection with influenza A (H3N2) and associated illness and the prevention of transmission of infection to adult members of the child's family. One hundred ten volunteers from 29 families completed this study during a naturally occurring outbreak of influenza A (H3N2). Influenza infections, defined as a positive viral throat culture or a 4-fold increase in antibody titer, occurred in 31.0% of children in the placebo group and 7.4% in the rimantadine group (P = 0.026). Clinical illness with laboratory evidence of influenza infection occurred in 24.1% of children in the placebo group and none in the rimantadine group (P = 0.007). Rimantadine was well-tolerated by the children, with no significant difference in reported adverse effects between the placebo and rimantadine groups. A combined analysis by families of these data and those of our similarly designed 1984 study, revealed that families in whom the children were given rimantadine had a significantly lower rate of influenza A infection and influenza-like illness compared with the families in whom the children were given placebo (68.8% vs. 18.8%, P less than 0.001) and (56.3% vs. 12.5%, P less than 0.001), respectively. We conclude that rimantadine prophylaxis of children appears to be an effective method to prevent influenza A (either H1N1 or H3N2) infection and illness in children.