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Prophylactic Antiviral Also Could Ease Flu Vaccine Shortages

An antiviral drug is being made available as an added public health safeguard in the face of recent shortages in U.S. influenza vaccine supplies. Late last year, officials at the Food and Drug Administration (FDA) approved a request from Hoffmann-La Roche of Nutley, N.J., that it be permitted to market Tamiflu as a drug to protect recipients against influenza infections.

A year earlier, agency officials approved Tamiflu, which was codeveloped with Gilead Sciences of Foster City, Calif., for use in treating influenza infections occurring among adults and adolescents. Unlike the flu vaccine, this orally administered drug has broad activity against both type A and B influenza viruses. It works by targeting one of the two major surface structures of the influenza virus, the neuraminidase protein, which is virtually the same in all common strains of influenza. By blocking this target, the drug prevents the virus from infecting new cells.

The application for prophylactic use of Tamiflu is supported by findings from three separate phase III clinical trials, according to the company. In one trial, daily administration of the drug for seven days reduced the incidence of influenza by 92% in adults and adolescents who were in contact with a household member infected with the flu. In another trial, it reduced the incidence of influenza by 76% in healthy adults during a community outbreak and, in the third trial, by 92% in the elderly in residential nursing home settings.

FDA Overrules Advisory Panel, Approves Flu Drug

In a separate development late in 1999, FDA approved a different antiviral drug, called Relenza, that is made by London-based Glaxo-Wellcome, for use in treating influenza infections (ASM News, October 1999, p. 669). Relenza is delivered by an inhaler device, and it appears to be most effective in relieving symptoms and shortening their duration when administered within the first two days of the onset of illness.

Jeffrey L. Fox