influenza prevention and control: past practices and future prospects

Influenza Prevention and Control

Past Practices and Future Prospects

DAVID S. FEDSON, M.D. Charlottesville, Virginia

The Immunization Practices Advisory Committee (ACIP) recommends annual influenza vaccination for elderly and high-risk persons [l]. This policy reflects continued recognition of influenza as an important cause of serious morbidity and excess mortality. Despite advances in medical care, there is little evidence to suggest that the impact of influenza is declining [2]. On the contrary, because the number of elderly persons is increasing, influenza appears destined to remain a significant health problem.

The traditional approach to the prevention and control of influenza has focused on influenza vaccine, and particularly on its use by office-based physicians. It is widely acknowledged, however, that current immunization efforts are inadequate and that newer approaches to vaccine delivery are required. This report begins with a historical review of the use of influenza vaccine in the United States. Next, three methods of improving immunization practice are discussed. Finally, future prospects for improving influenza immunization are presented.

tNFCUENZA tMMUNtZATtON PRACTtCES IN THE UNtTED STATES: 1966 TO 1965

From the Department of Medicine, U?iversity of Virginia School of Medicine, Charlottalkville, Vir- ginia. Requests for reprints should be addressed to Dr. David S. Fedson, Box 494, University of Vir- ginia Medical Center, Charlottesville, Virginia 22908.

There are two sources of information on the use of influenza vaccine in the United States. The first set of data comes from the reports of vaccine manufacturers to the Centers for Disease Control (CDC). These reports, which are published in Biologics Surveillance, document the national sales and distribution of influenza vaccine, net of returns. The second set of data comes from the United States Immunization Survey, which is conducted in September of each year as part of the Household Interview Survey of the Bureau of the Census. Both sets of data can be regarded as macroepidemiologic in nature; they indicate the overall extent of influenza immunization, but they provide no information on its microepidemiology- on who is giving, and who is receiving, the vaccine.

The data on use of influenza vaccine for the period from 1968 through 1985 are summarized in Figure 1. In general, the yearly figures on doses of vaccine distributed and number of persons immunized are similar. Dur- ing six of the first eight years, more than 17 million doses were distributed annually. Immunization rates for persons 65 years and older exceeded 17 percent. For persons aged 20 to 64 years with high-risk conditions, immunization rates for the three years for which data are available ranged from 13.2 to 16.6 percent. Among all persons receiving influenza vaccine, these two groups accounted for less than 40 percent of those immunized. During the national swine influenza immunization program of 1976-l 977, by contrast, 85.4 million doses of vaccine were distributed, and 37.7 percent of elderly persons and 32.1 percent of younger high-risk persons were immunized. For several years following the swine influenza pro-

42 June 19, 1987 The American Journal of Medicine Volume 82 (suppl 6A)

SYMPOSIUM ON INFLUENZA-FEDSON

Figure 7. Influenza immunization in the United States: 1968 to 1985. Total net doses of influenza vaccine distributed are reported in Biologics Surveillance, CDC, Atlanta, Georgia. Numbers and percentages of persons immunized are reported as published (1968 to 1978) and unpublished (1979 to 1985) data in the United States Immunization Survey, C/X, Atlanta, Georgia. I

I I, I I I I I I I I I I I I I, I

1968.69 1972.73 1976.77 1960.61 1964.65

gram, vaccine distribution returned to levels similar to those seen in the early 1970s. However, in 1984-1985, only 14.2 million doses were distributed. More important, during the six-year period beginning in 1979-I 980, fewer than 16 million persons of all ages were immunized each year-an immunization level lower than any achieved since 1968-l 969.

In recent years, annual immunization rates for persons 65 years and older have averaged 21 to 23 percent, but rates have fallen to approximately 10 percent for younger high-risk persons. Also, fewer non-high-risk persons have been receiving influenza vaccine. The two high-risk groups shown in Figure 1 accounted for 31 percent of all persons vaccinated in 1972-1973; in 1984-1985, they accounted for 56 percent of those immunized.

These macroepidemiologic data document the lack of improvement in influenza immunization in the United States. Despite the detailed recommendations of the ACIP on influenza prevention and control, vaccination of elderly persons has remained essentially unchanged, while immunization of both younger high-risk and non- high-risk persons has shown a steady decline. These figures indicate that unless there are fundamental changes in vaccination practices, there is little reason to expect substantial improvement in influenza immunization.

METHODS OF IMPROVING INFLUENZA IMMUNIZATION PRACTICE

The historical pattern of influenza immunization in the United States indicates a strong need for newer approaches to vaccine delivery. In other areas of medical care, numerous studies have examined ways in which

TABLE I Methods for Improving Influenza Immunization Practice

l Educational programs l Administrative and organizational changes l Incentives and disincentives

physician practices can be modified and improved [3]. In general, three methods can be considered for improving influenza immunization practices (Table I). Educational Programs. Expanded educational programs have been advocated as one method of encourag- ing better performance in the delivery of the influenza vaccine. For most persons, education means greater empha- sis in the training of health-care professionals on the seriousness of influenza as a disease and the safety and effectiveness of influenza vaccine. Underlying this approach is the assumption that improved understanding will be re- flected in improved immunization practice.

Although educational programs are clearly necessary, there is much to suggest that they will not be sufficient by themselves. Evidence for this comes from a survey conducted by the CDC on physicians’ attitudes toward influenza and influenza vaccine (Tables II and Ill) [4]. Among office-based general practitioners, family practitioners, and internists, more than 80 percent recognized that influenza is a very serious disease for elderly persons with high-risk conditions. More than half regarded influenza as very serious for younger high-risk persons. Almost all physicians agreed that persons with high-risk conditions should be immunized, and most acknowledged the need

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TABLE II Physicians’ Attitudes Toward Influenza and Influenza Vaccine, 1980*

General and Family Practitioners Internists

VW (289)

Influenza is a very serious disease 265 years 41+ 31 ~65 years HRC a5 a1 ~65 years HRC 63 54

Most persons should receive influenza vaccine

265 years 84 74 ~65 years HRC 98 98 ~65 years HRC 97 96

Influenza vaccine is very safe 76 77 Moderately safe 22 23 Safer now than 15 years ago 85 82

Influenza vaccine effectiveness is 280% 45 42 260% 72 74

Annual immunization is required 93 94 Usually glve influenza vaccine to

some patients 91 92

HPC = high-risk condition. *The analysis was based on the responses of 299 general and family practitioners and 289 internists who were randomly selected from among those listed in the American Medlcal Association’s Directory of office-based physicians. They were surveyed by telephone in August and September 1980. The responding general and family practitioners and internists represented 55 and 51 percent, respectively, of all qualified physicians in the two samples who were contacted. Adapted from unpublished data, CDC. +Percent of responding physicians.

for influenza vaccination for patients with a variety of specific conditions (Table III). In addition, virtually all physicians regarded the vaccine as safe, and most correctly recognized that current vaccines are safer than those used before the introduction of modern techniques of vaccine production. These physicians also revealed accurate understanding of the vaccine’s effectiveness in preventing disease. Finally, more than 90 percent agreed that annual immunization is required, and said they usually gave influenza vaccine to some of their patients.

The macroepidemiologic information on the use of influenza vaccine shown in Figure 1 reveals a wide difference between what physicians say they do and what actually is done in practice. Further evidence to substantiate this dis- crepancy has come from a study of the immunization practices of internists [5]. In this study, which was conducted in the fall of 1981, physicians were selected at random from a 1978 cohort of internists with geheral, primary care, or subspecialty training. They were asked to keep log diaries of their practice activities, including information on the characteristics of patients and whether these patients had been given vaccines (any vaccine, not influenza

vaccine alone). The immunization rates for the patients for whom the physicians said they provided primary care are shown in Table IV. Overall, fewer than 10 percent of elderly persons-and only 3 percent of younger persons with high-risk conditions-received any vaccine. These results demonstrate the point prevalence of immunization activity among office-based internists. They provide microepidemiologic documentation that few persons with indications for influenza vaccine were beihg immunized.

The low rates of immunization observed in the study of physicians’ practices, together with the national data from the CDC, provide solid evidence that, for all their apparent understanding of the importance of influenza and influenza vaccine, physicians fail to translate their knowledge into clinical practice. From this it is reasonable to conclude that educational programs that focus on conventional knowledge about the disease and its prevention are un- likely to bring about major improvements in the delivery of influenza vaccine. Administrative and Organizational Changes. If there are any doubts that educational programs alone will im- prove influenza vaccination practices, it is clear that administrative and organizational changes can greatly im- prove immunization rates for high-risk patients. Most reports have described programs in the outpatient clinics of teaching hospitals [8,7]. Many different approaches have been used to encourage immunization, including letters and postcards to patients, notices placed in patient charts, and computer-generated reminders to physicians that they should immunize their high-risk patients. Although physicians themselves have, as a rule, planned these programs, the programs have, in most instances, been imple- mented by nurses and other health-care personnel. The specific form of intervention has not seemed important; regardless of the approach taken, vaccination rates of 50 to 70 percent or more have regularly been achieved among high-risk patients. The common denominator in all these studies has been the fact that organized programs guarantee that almost all high-risk patients will be offered the influenza vaccine. Once the vaccine is offered, high immunization rates inevitably follow.

Other important lessons have been learned from outpatient clinic studies of influenza immunization. For example, when immunization in clinics with and without organized programs were compared, those with organized programs were five to 70 times more successful in deliv- ering influenza vaccine [8]. Such programs were shown to be self-sustaining from year to year. Also, it has been stated repeatedly that approximately 20 percent of high- risk persons receive influenza vaccine each year, but whether persons who are immunized in one year are likely to receive vaccine in subsequent years has been quite uncertain. Many practicing physicians have noted anec- dotally that the same patients get influenza vaccines year after year. This has been borne out in one report from a



TABLE III Physicians’ Attitudes about Patients Who Need and Usually Are Given Influenza Vaccine, 1980*

Patient Group

Patients Need Influenza Vaccine


(299)+ W9)

Patients Usually Are Given Influenza Vaccine


(272)* (267)

Elderly (265 years) 89§ 87 89 89 Chronic pulmonary disease 94-96 94-96 93-95 95-97 Heart disease 90 87 90 90 Chronic renal disease 83 86 69 76 Diabetes mellitus 79 82 76 83 lmmunocompromised status 73 78 60 72 Severe anemia 71 68 55 52 Chronic neurologic conditions 61 55 55 47 Health-care providers 65 54 57 43

*Adapted from unpublished data, CDC. +Number of qualified physicians responding. *Number of responding physicians who usually administer influenza vaccine to their patients §Percent of responding physicians.

TABLE IV Immunization Practices among Internists, 1981

Physician Group*

Patients 2 66 Years

Number Percent Immunized’

Patients 565 Years, High-Risk

Number Percent Immunized+

All internists 1,265 8.7 1,370 3.1 General internists 644 8.7 639 3.3 Primary care internists 220 12.3 299 4.7 Subspecialty internists 401 6.7 432 1.9

l Physicians were selected at random from a 1976 cohort who had completed training in traditional internal medicine programs, primary care programs, or subspecialty fellowship programs. +Percent of patients who received any vaccine, not just influenza vaccine. Adapted with permission from [5].

teaching hospital’s outpatient clinic [9]. Among patients who were immunized in one year, and who returned to the clinic the following year during the period when vaccine was offered, 72 percent were re-immunized. This suggests that the receipt of vaccine has a training effect on patients; once immunized, they will expect the vaccine to be offered the next year, and if necessary they will ask for it in subsequent years.

As noted earlier, most persons who are immunized probably receive their influenza vaccine in the office- practice setting. Surprisingly, there are no reports describ- ing the immunization experiences of office-based physicians, although in all likelihood those who are successful have an organized approach to offering vaccine. The hospital is also an appropriate site for influenza immunization. Recent evidence suggests that, in addition to age and underlying high-risk conditions, previous hospital care is a useful marker for identifying persons who should be vaccinated. During influenza epidemics approximately 30 to 40 percent of the patients who are admitted to hospitals with

June 19,1987

respiratory conditions have been discharged at least once during the previous year [lO,ll]. In one population-based study of Medicare enrollees, approximately 27 percent of persons hospitalized with acute and chronic respiratory conditions during an epidemic period had been discharged at least once since September 1 of the preceding year [12]. The risk of being admitted with influenza- related disease was five times greater among persons with a previous discharge during this four to five-month period than it was among those who had not been discharged. Also, among all persons admitted with respiratory conditions, there was a significantly greater risk of death among those with an episode of previous hospital care than among those without a previous hospital admis- sion.

These findings provide an epidemiologic rationale for the current ACIP recommendation that highest priority for influenza vaccination should be given to persons with conditions that have required regular medical follow-up or hospitalization during the previous year [l]. Experience

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with implementing this recommendation by offering influenza vaccination to patients at the time of hospital discharge is limited, and in one instance it has been disap- pointing [l 11. However, influenza vaccination rates for discharged elderly patients can approach 80 percent if the program is well organized (H.G. Bloom, personal commu- nication).

The effectiveness of organized approaches to influenza vaccine delivery has been most comprehensively demon- strated in studies of nursing homes [13]. On average, approximately 55 to 85 percent of nursing home residents are vaccinated in any given year. An immunization rate of 80 percent or more is usually necessary to induce herd immunity, and where this goal is achieved, only sporadic cases, rather than institutional outbreaks of influenza, are observed. Perhaps the most practical finding from these studies is the importance of the nursing home’s consent policy. Whenever written consent from a family member was required, only 57 percent of residents were immunized. When there was no requirement for written consent, 90 percent received the vaccine. Thus, a simple administrative factor is the critical determinant in achieving immunization rates necessary to prevent outbreaks of influenza in nursing homes.

In considering the importance of administrative and organizational changes for improving influenza vaccine delivery in the office-practice setting, in hospitals, and in nursing homes, one additional point must be stressed: Any plan to conduct a vaccination program will fail if there is insufficient vaccine available for use. Orders for influenza vaccine are generally placed in the late fall and win- ter preceding the year in which the vaccine will be used. These orders allow manufacturers to decide how much vaccine to produce. Although uncommon, there have been occasions when immunization programs have run short of vaccine. A properly organized influenza vaccination program should begin with a determination of the size of the target population and an estimate of what propor- tion will be offered the vaccine and immunized. Based on these figures, a sufficient supply of vaccine can be or- dered. Incentives and Disincentives. In practically every sphere of human activity, changes in behavior can be in- duced by an appropriate mix of incentives and disincentives. This approach has yet to be tried for influenza immunization, but there is no reason to think that in certain circumstances it would not be successful here as well. Incentives and disincentives can be monatary or non- monetary. For influenza vaccination, they would be appli- cable primarily to the providers of health care rather than to patients. To some extent, influenza vaccination already provides a monetary incentive for office-based physicians. In the CDC survey of physician attitudes referred to earlier, 13 percent of the respondents disapproved of expanded

public immunization programs because they would interfere with the business aspects of their practices [4].

At the institutional level, however, incentives and disincentives could become important. Several potential appli- cations might be considered. For health maintenance organizations and other providers of prepaid health care, there is a positive economic incentive to prevent illness among enrollees with measures as cost-effective as influenza vaccination [14]. Yet there is no evidence to suggest that the use of influenza vaccine is any greater in these organizations than it is in fee-for-service practices.

Another application of monetary incentives and disincentives could be in the reimbursement rates negotiated by hospitals and insurance companies for the care of patients with influenza-related diseases. If the cost-effectiveness of immunizing discharged patients can be reliably estimated, insurance companies may be persuaded to negotiate higher reimbursement rates for hospitals that demonstrate high rates of vaccinating discharged patients. For Medicare patients, the diagnosis-related group payment for an episode of influenza-associated illness might differ for hospitals with high and low rates of patient immunization.

Within hospitals themselves, administrators recognize the higher costs of hiring temporary staff to fill in when regular staff become ill during influenza outbreaks [15]. They have a financial incentive to undertake staff immunization programs. These programs might include a requirement for staff who work with high-risk patients-and who choose not to be immunized-to sign an “informed refusal” form. This could include acceptance of the possi- bility of reassignment to another work area in the event of a community or hospital outbreak of influenza.

Finally, and above all else, there is a need to change the federal policy that prohibits Medicare payment for influenza immunization. Pneumococcal immunization has qualified for Medicare reimbursement since 1981. It is difficult to understand why the federal government strongly recommends the use of both vaccines and at the same time pays for one but not the other. It is even more difficult to understand the reluctance of the federal government to spend less money for prevention than it is otherwise obli- gated to spend for the care of persons in whom influenza develops [14].

FUTURE PROSPECTS FOR IMPROVING INFLUENZA IMMUNIZATION

Much of the discussion regarding the influenza vaccine is focused on differing estimates of its efficacy. Although efficacy is important, it is not the sole determinant of the vaccine’s effectiveness. If, for example, among 100 persons in whom serious influenza will develop, only IO persons are vaccinated with a vaccine that is 80 percent effi-



cacious, only eight illnesses will be prevented. On the other hand, if the vaccine has an efficacy of only 40 percent but 80 percent of those 100 persons are vaccinated, then 32 illnesses will be prevented. Clinicians can do nothing to modify the efficacy of influenza vaccine, but their efforts to immunize their patients have everything to do with the vaccine’s effectiveness. Only recently has at- tention been given to research that is focused on the de- terminants of successful immunization practice. Patients would no doubt be better off if knowledge of the epidemiology of influenza vaccination matched that of the disease the vaccine is designed to prevent.

On the basis of what is currently known, it can be con- cluded that most physicians have adequate knowledge of the seriousness of influenza and the safety and efficacy of influenza vaccine. However, the vaccine is greatly under- used because physicians fail to translate their knowledge into clinical practice. Simple reiteration of the ACIP rec-

1.

2.

7.

8.

ommendations for the prevention and control of influenza becomes an exercise in clinical piety if it does not lead to meaningful improvement in immunization practices.

Administrative and organizational changes have been shown to bring major improvements in the delivery of the influenza vaccine. Many methods have been used, and all have been successful when they ensure that high-risk persons are offered the vaccine. Needed organizational changes must include recognition that hospitals can and should play a central role in the prevention of influenza. In these and other institutions, a judicious mix of incentives and disincentives has the potential for bringing further improvements in influenza vaccine delivery. A change in federal policy permitting Medicare reimbursement for influenza immunization would be of fundamental importance in guaranteeing more widespread use of the influenza vaccine and would thereby contribute to maintaining the health and well-being of all elderly Americans.

REFERENCES

Recommendations of the Immunization Practices Advisory Committee (ACIP): Prevention and control of influenza. MMWR 1986; 35: 317-326, 331.

Lui KJ, Kendal AP: Impact of influenza epidemics on mortality in the United States from October 1972 to May 1985. Am J Pub- lic Health 1987; 77: 712-716.

Eisenberg JM: Physician utilization. The state of research about physicians’ practice patterns. Med Care 1985; 23: 461-483.

Centers for Disease Control: Attitudes and practices of private physicians related to influenza and pneumococcal immunization, 1980. Atlanta, January 30, 1981, unpublished data.

Fedson DS, Gifford BS, Schleiter MK, Tarlov AR: Epidemiology of immunization practices among internists (abstr). Clin Res 1964; 32: 644A.

Fedson DS: Immunizations for health care workers and patients in hospitals. In: Wenzel RP, ed. Prevention and control of nos- ocomial infections. Baltimore: Williams & Wilkins, 1986; 116- 174.

Fedson DS: Influenza and pneumococca I immunization strate- gies for physfcians. Chest 1987; 91: 436-443.

Fedson DS: Influenza and pneumococcal immunization in medical clinics: 1971-1983. J Infect Dis 1984; 149: 817-818.

9. Ratner ER, Fedson DS: Influenza and pneumococc al immunization in medical clinics, 1978-1980. Arch Intern Med 1983; 143: 2066-2069.

10. Barker WH, Mullooly JP: Pneumonia and influenza deaths during epidemics: implications for prevention. Arch Intern Med 1982; 142: 85-89.

11. Fedson DS, Kessler HA: A hospital-based influenza immunization program, 1977-78. Am J Public Health 1983; 73: 442- 445.

12. Hamard MP, Kaiser DL, Reid RA, Fedson DS: Hospital-based influenza immunization: epidemiologic rationale from the Shenandoah Study. Clin Res 1987; 35: 6A.

13. Arden NH, Patriarca PA, Kendal AP: Experiences in the use and efficacy of inactivated influenza vaccine in nursing homes. In: Kendal AP, Patriarca PA, eds. Options for the control of influenza. New York: Alan R. Liss, Inc., 1966; 155-168.

14. Riddiough MA, Sisk JE, Bell JC: Influenza vaccination: cost effectiveness and public policy. JAMA 1983; 249: 3189- 3195.

15. Hammond GW, Cheang M: Absenteeism among hospital staff during an influenza epidemic: implications for immunoprophy laxis. Can Med Assoc J 1984; 131: 449-452.

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influenza prevention and control: past practices and future prospects

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