Advances in the prophylaxis and treatment of influenza illness. Based on a presentation by Frederick G. Hayden, MD.

Vaccine represents the primary means of preventing influenza. Although influenza vaccines provide a high rate of protection in young and ambulatory elderly, a lower rate of protection occurs in the frail elderly and immunocompromised hosts. Researchers have developed new vaccine strategies that use live attenuated, cold-adapted virus vaccines. In children, this cold-adapted influenza vaccine appears to offer broader protection than the classic inactivated vaccine given by injection. It was protective against an antigenic variant, and by protecting against influenza, it reduces influenza-related complications, such as otitis media and lower respiratory tract illness, as well as lessens antibiotic use associated with these complications. Cold-adapted vaccine is well tolerated and represents a very exciting advance in influenza vaccines. Two drugs, amantadine and rimantadine, have received Food and Drug Administration approval for the prophylaxis and treatment of influenza A virus infection. However, their use is limited by side effects, particularly with amantadine, in elderly people (an activity limited to influenza A) and the emergence of resistance. A new class of specific anti-influenza agents, the neuraminidase inhibitors, has demonstrated potent inhibition of both influenza A and B viruses. Two neuraminidase inhibitors, inhaled zanamivir and oral oseltamivir, have reached advanced clinical development and were approved for treatment of acute influenza in the United States in 1999. Both drugs have shown clinical efficacy both in treating and preventing influenza illness.