Influenza, influenza vaccine, and amantadine/rimantadine.

Influenza viruses are highly contagious viruses that are transmitted from person to person, usually by the airborne route. Persons in semi-closed or crowded environments, such as students and residents of nursing homes, are at high risk of exposure. The illness attack rate in children ranges from 14% to 40% yearly. Fatality rates are highest in persons who have chronic medical conditions, such as chronic obstructive lung disease, cardiovascular disease, and diabetes mellitus, particularly if they are elderly. The effectiveness of influenza vaccine in preventing or attenuating illness varies, depending primarily on (1) the degree of similarity between the virus strains included in the vaccine and those that circulate during the influenza season, and (2) the age and immunocompetence of the vaccine recipient. When there is a good match between vaccine and circulating viruses, influenza vaccine has been shown to prevent illness in approximately 70% to 90% of healthy persons less than 65 years of age. Adverse events following influenza vaccine include mild, local reactions at the injection site (up to 20%) and occasionally fever in approximately 1% of vaccinees. Despite the availability of an effective vaccine, only 55% of persons 65 years of age and older reported receiving influenza vaccine in 1994. Vaccination levels are even lower in persons less than 65 years of age with high-risk medical conditions. Important procedures to improve vaccination rates are (1) assessment of a practice's or medical facility's current vaccination rates, (2) identification of target populations for vaccination, (3) formation of a specific goal (ie, percentage of target population to be immunized), (4) development of a plan of action, and (5) provision of ongoing feedback to the individual physicians about vaccination rates of their own patients.