Influenza continues to be a major cause of morbidity and mortality in the United States. Each year, approximately 20,000 deaths and 110,000 hospitalizations occur because of influenza.¹ Rates of infection are highest in children, but rates of serious morbidity and mortality are highest in persons 65 years of age or older and in persons who have medical conditions that place them at high risk for serious complications from influenza.

Rates of influenza-associated hospitalization are lowest in young adults, but rates of influenza-associated hospitalizations begin increasing in adults who are about 45 years of age with high-risk conditions. Among those persons with high-risk conditions, the rate of hospitalization associated with influenza is approximately 40 to 60 per 100,000 population in those who are 15 to 44 years of age, compared with a rate of approximately 80 to 400 per 100,000 population in those who are 45 to 64 years of age. In all persons 65 years of age or older, influenza-associated hospitalization rates have ranged from approximately 200 to more than 1,000 per 100,000 population.¹

The proportion of persons 65 years of age or older who have received the influenza vaccine increased from 33 percent in 1989 to 65.5 percent in 1997.^1,2 Among persons less than 65 years of age who are at high risk for influenza-related complications, vaccination rates are less than 30 percent.³ Increasing vaccination coverage among these high-risk groups is the highest priority for expanding influenza vaccine use.

As indicated in Zimmerman's article⁴ in this issue of American Family Physician, the American Academy of Family Physicians (AAFP) has made an aggressive move by lowering the age of universal influenza vaccination to 50 years. Zimmerman refers to the 1995 National Health Interview Survey data that indicate the rate of vaccination is only 38 percent in persons 50 to 65 years of age who are at risk for complications of influenza.³ He argues that this low rate is in part caused by the difficulty in identifying persons who are at risk for complications of influenza, either because the persons are unaware they have a high-risk condition or because the clinician has difficulty in implementing an adequate manual or computerized reminder system based on high-risk conditions. He further acknowledges the limited success of other vaccination strategies for other high-risk groups.⁴

The assumptions that Zimmerman⁴ has made about the factors that contribute to the low vaccination rate in adults 50 to 64 years of age should be addressed. Because many medical organizations are recommending that all adults be evaluated at age 50 for a variety of diseases and preventive interventions, why are patients not being made aware of high-risk conditions that they have? If those patients are simply not seeking health care, is it logical to assume that they will just have an influenza immunization?

The implementation of a reminder system based on risk conditions has its difficulties. The cost of personnel for risk assessment and the cost of telephone or mail reminder systems may not be recovered from charges associated with vaccination. Electronic reminder systems can be readily programmed, but they also have costs associated with them. How to underwrite these costs becomes an issue. However, in an era of managed care, should insurance companies partner with physicians in developing programs that would identify persons with high-risk conditions, because the literature clearly shows a cost savings with influenza vaccination?

When a shift in strategy occurs from vaccinating primarily those who are at greatest risk from complications of influenza to include otherwise healthy adults, then the cost-benefit of this strategy also needs to be closely examined. Although Nichol and colleagues⁵ have shown cost savings from vaccinating working adults against influenza, the magnitude of this benefit relies on a close antigenic match between the circulating influenza strain and the influenza vaccine strain and a relative high attack rate of influenza infection.⁶ Furthermore, most of the cost savings associated with vaccination was in avoiding lost wages and not in direct cost savings.⁵

Despite these questions and comments, Zimmerman⁴ and the AAFP make a solid argument for vaccinating all adults 50 to 64 years of age. However, physicians should not forget there are persons in all age groups with indications to receive the influenza vaccine, either because they have a medical condition that places them at high risk of complication from influenza or because they are at risk of transmitting influenza to those who are at high risk. Physicians, therefore, still must develop a mechanism to identify these persons so that they may benefit from the vaccine.