Prevention and control of influenza.

Influenza is arguably the most important cause of acute upper respiratory tract infection in humans. Epidemics associated with influenza viruses are responsible for more deaths in the United States than any other vaccine-preventable disease. (1-4) Approximately 20,000 excess deaths and 200,000 hospitalizations each year in the United States occur as a result of these infections. (1) All age groups are affected, the virus is highly communicable, and it can reinfect and thus cause repeated infections throughout life. (1,5) The mainstay of influenza prevention and control is the trivalent inactivated influenza vaccine (TIIV). Annual administration of TIIV is a cost-effective approach for the prevention of influenza, especially in years when there is a good antigenic match between the dominant circulating wild-type virus and the strains included in the vaccine. (1,4) The vaccine is safe, inexpensive, and, most important, effective in reducing illness caused by influenza, associated pneumonia, exacerbation of cardiopulmonary disease, otitis media, and all-cause mortality. Furthermore, sick leave and physician's office visits are reduced in vaccinated individuals. (1-3,6-13)

Trivalent Inactivated Influenza Vaccine

TIIV was originally developed in the 1940s. (14) Over the years, the vaccine has proved to be quite safe and immunogenic (ie, stimulates the humoral immune system). (1,6,7) Specifically, in approximately 90% of adults, 15 [micro]g intramuscular (IM) TIIV (0.5 ml of 30-[micro]g/ml preparation) results in the production of a protective hemagglutinin antibody within 2 weeks. (1) A normal response to the vaccine is usually seen in patients with chronic lung disease, collagen vascular diseases, and even in recipients of moderate doses of glucocorticosteroids. Certain high-risk individuals, however, have a decreased immune response. The elderly, individuals with renal disease, recipients of renal transplants, and patients with late-stage acquired immunodeficiency syndrome may have decreased responses to TIIV. (1) For example, only 50% of residents of long-term care facilities (LTCFs) develop protective vaccine-induced antibody titers. (15)

The vaccine is most effective when the strains included in the vaccine are a good antigenic match with the circulating strains of influenza. (1) The currently licensed TIIV contains contemporary circulating strains of influenza A (H1N1), influenza A (H3N2), and influenza B virus. (1,7) The U.S. Food and Drug Administration's (FDA's) Vaccines and Related Biological Products Advisory Committee recommended that the 2002-2003 TIIV contain A/New Caledonia/20/99-1ike (H1N1), A/Moscow/10/99-1ike (H3N2), and B/Hong Kong/ 330/01-like viruses. (1,7) The process of strain selection for TIIV can be viewed as the result of several educated guesses that include consideration of the molecular characterization of circulating strains of influenza from around the world as well as assessment of viral growth characteristics in chicken embryos and the measurement of various strains' abilities to induce antibody production. Predictions of circulating strains are made at least 6 months in advance because of the amount of time typically needed to produce the vaccine. (1,6,7)

Other Influenza Vaccines

Several new influenza vaccines are under development. Investigators are exploring ways to increase the immunogenicity and durability of the vaccine, to allow for easier routes of administration, to expand coverage of the vaccine, and to provide immunity to potentially new species such as H5N1. Some of the new vaccines have used either protein or nucleic acid adjuvants, and others have focused on potential antigenic sites other than hemagglutinin or neuraminidase. (4,14,16-19)

A new and interesting approach to influenza vaccine development is the intranasally administered, cold-adapted, live attenuated influenza virus vaccine (LAW). LAIVs, which have been in development in the United States since the 1960s, consist of live influenza viruses that replicate in the upper respiratory tract but replicate poorly at temperatures found in the lower respiratory tract. Possible advantages of LAIVs are their potential to induce a broad mucosal and systemic immune response and the anticipated acceptability of intranasal rather than IM administration. (1,5,19-23)

In a 1996-1997 study of children from 15 to 71 months of age, an intranasally administered trivalent LAIV was 93% effective in preventing culture-positive influenza A (H3NZ) and influenza B infections, and it reduced febrile otitis media and the use of antimicrobial medication to treat otitis media. (20) In a follow-up study in 1997 and 1998, the trivalent LAIV was 86% effective in preventing culture-positive influenza infection in children, despite a suboptimal match between the vaccine's influenza A (H3NZ) component and the predominant circulating influenza A (H3NZ) virus. (21) A study conducted among healthy adults during the same season demonstrated a 25% reduction in febrile respiratory illness and a 25% reduction in lost work days. (22) No study to date has directly compared the efficacy of TIIV and trivalent LAIVs. Most recently, in a double-blind, placebo-controlled study, an LAIV for influenza A and B demonstrated 93% effectiveness in preventing culture-proved influenza infection. Additional efficacy data for patients aged 50 years and older have been requested. The increased risk of asthma in children 18 to 35 months of age who were administered LAIV resulted in the current recommendation to the FDA from the advisory committee to limit its approval to individuals between 5 and 49 years of age.

In June 2003, the FDA approved FluMist (MedImmune, Inc., Gaithersburg, MD). FluMist (Influenza Virus Vaccine Live) Intranasal is a live, trivalent, nasally administered vaccine intended for active immunization to prevent influenza. The vaccine contains LAIV that replicate in the nasopharynx of the recipient and are shed in respiratory secretions. Each 0.5-ml dose is formulated to contain LAIV of the strains A/New Caledonia/20/99 (H1N1), A/Panama/2007/99 (H3NZ) (A/Moscow/10/99-like), and B/Hong Kong/330/2001. The vaccine is indicated for active immunization for the prevention of disease caused by influenza A and B viruses in healthy children and adolescents from 5 to 17 years of age and healthy adults from 18 to 49 years of age. It is not indicated for children younger than 5 years of age or for adults 50 years of age and older. (23)

Adverse Effects and Contraindications Related to the Vaccine (TIIV)

The only absolute contraindication to vaccination with TIIV is an anaphylactic hypersensitivity reaction to eggs. (1) Relative contraindications in which TIIV should probably be avoided include children younger than 6 months of age and pregnant women in their first trimester of pregnancy. People with acute febrile illness usually should not be vaccinated until their symptoms have abated. Minor illnesses such as mild upper respiratory tract infections, even if with a mild fever, do not contraindicate administering TIIV. (1) People who have a history of a true anaphylactic hypersensitivity reaction to eggs but are at high risk for complications as a result of influenza can benefit either from the prophylactic use of antiviral agents or, after an appropriate allergy evaluation and desensitization, vaccination with TIIV. (1) Table 1 lists the absolute and relative contraindications to influenza vaccination with TIIV. (1)

Several randomized, controlled trials have demonstrated that TIIV is safe and well tolerated in almost all age groups. It has been estimated that approximately 25% of all recipients develop discomfort at the injection site within the first 24 hours but that only approximately 5% of recipients develop pain and swelling at the site. Headaches and myalgias occur at the same rate as placebo. TIIV does not and cannot cause a respiratory tract illness. The contents of the currently used influenza vaccine are inactive and "killed." Any respiratory tract illness that develops shortly after an inoculation of TIIV is simply coincidental and usually represents an upper respiratory tract infection secondary to another virus that can cause a flulike illness. In adults, reactions to the whole virus and split product vaccines are similar. In children, however, whole virus vaccines are associated with a higher rate of fever. Because of their decreased potential to cause febrile reactions, only split virus vaccines should be used in children younger than 13 years of age. Split virus vaccine might be labeled as split, subvirion, or purified surface antigen vaccine. (1)

Influenza vaccine distributed in the United States might also contain thimerosal. Thimerosal is a mercury-containing compound that has been used as a preservative since the 1930s. Although no evidence of harm caused by low levels of thimerosal in vaccines has been reported, in 1999, the U.S. Public Health Service and other organizations recommended that efforts be made to reduce the thimerosal content in vaccines to decrease total mercury exposure, chiefly among infants and pregnant women. Because of the known risks for severe illness as a result of influenza infection and the benefits of vaccination, however, and because a substantial safety margin has been incorporated into the health guidance values for organic mercury exposure, the benefit of influenza vaccine with reduced or standard thimerosal content outweighs the theoretical risk, if any, from thimerosal. (1)

With regard to Guillain-Barre syndrome (GBS), available data have not demonstrated a statistically significant association between the use of influenza vaccine and the occurrence of GBS. The incidence of GBS among the general population is low, but people with a history of this condition have a substantially greater likelihood of subsequently developing GBS than do individuals without such a history. Thus, the likelihood of coincidentally developing GBS after influenza vaccination is expected to be greater among people with a history of the GBS than among people with no history of GBS. Whether influenza vaccination specifically increases the risk for recurrence of GBS is unknown. Therefore, it is probably prudent to avoid vaccinating people who are not at high risk for severe influenza complications and are known to have developed GBS within 6 weeks after a previous influenza vaccination. (1)

In other studies, no statistically significant association was demonstrated between the administration of TIIV and exacerbation of cardiopulmonary disease or collagen vascular diseases such as rheumatoid arthritis and systemic lupus erythematosus. The vaccine has not been associated with significant adverse events in individuals with renal disease or in organ transplant recipients, and it is safe to administer to people with human immunodeficiency virus (HIV) infection. With regard to the patients with HIV, it has been suggested that immune activation associated with TIIV may stimulate HIV replication. Some studies have shown transient and minor increases in the HIV viral load, whereas others have shown no effect. To date, these transient and minor increases in HIV viral load have been of little clinical consequence, and TIIV is clearly recommended for people with HIV infection. (1)

Recently, an oculorespiratory syndrome (ORS) manifested by the presence of bilateral red eyes, facial edema, or a variety of respiratory symptoms including coughing, wheezing, chest tightness, dyspnea, or sore throat was described in Canada during the 2000-2001 influenza immunization campaign. (24,25) In a double-blind, randomized, crossover study design, the risk of ORS was 6.3% after vaccine injection and 3.4% after placebo injection. ORS symptoms were mild, and vaccine-attributable general symptoms were infrequent. (24)

Both the 23-valent pneumococcal polysaccharide vaccine and TIIV can be coadministered at different sites without increasing side effects. However, influenza vaccine is administered every year, whereas pneumococcal vaccine is not. No studies have been conducted regarding the simultaneous administration of TIIV and other childhood vaccines. Inactivated vaccines do not usually interfere with the immune response to other inactivated or live vaccines. Thus, children who are at least of 6 months of age can receive influenza vaccine at the same time that they receive other routine vaccinations. (1)

Effectiveness of TIIV

In a number of randomized, controlled trials focusing on the prevention of influenza A in young adults, the administration of TIIV was approximately 80% effective and resulted in decreases in morbidity and absence from work or school. (1,3,8) Vaccine use also has a favorable impact on health care personnel. Studies show reduced morbidity and absenteeism from work. In another study in which LTCF personnel were vaccinated, a decrease in influenza-related morbidity and mortality in LTCF residents was demonstrated. (1,11,26)

Even more impressive are the results of TIIV administration in the elderly. A meta-analysis of published cohort observational trials in the elderly estimated a 56% decrease in respiratory illness. These trials also demonstrated a 50% decrease in influenza, pneumonia, and related hospitalization. (1,2,9,10,27) Recently, an observational study demonstrated that TIIV in two large elderly patient cohorts was associated with substantial reductions in the risk of hospitalization for cardiac disease (19%) and cerebrovascular accident (16-23%). (28) Of significance, and perhaps the most impressive result of this meta-analysis, however, was the 68% decrease in all-cause mortality. (1,2,9,10,27)

The cost of influenza vaccine is approximately $7/dose. (1) In two studies conducted from a society-wide perspective, costs ranged from a net savings of $47 per person vaccinated to a net cost of $11 per vaccination. Net savings in young adults are secondary to avoided losses in productivity, and in the elderly they are secondary to reduced medical costs. (1,2) To a degree, variations in vaccine efficacy are a function of the match between the vaccine strains and the circulating strain.

There are approximately 150 million Americans for whom vaccination is specifically recommended (Table 2). (1) Ironically, only approximately 80 million doses are produced annually in the United States. (1) This discrepancy has not been an issue, perhaps because of the poor vaccination rates. Specifically, in 1999, fewer than 70% of people older than 65 years of age reported having been vaccinated. (1) Similarly, only 31% of adults 18 to 64 years of age who had high-risk conditions were vaccinated. (1) Low vaccination rates also have been noted in pregnant women. (1)

Recommendations for TIIV Administration

Most adults 50 years of age and older and other target populations are candidates for influenza vaccination. (1) The typical target populations are listed in Table 2. In contrast to previous years, because young children are at increased risk for influenza-related hospitalization, influenza vaccination of healthy children aged 6 to 23 months is encouraged when feasible. The Centers for Disease Control and Prevention's (CDC's) Advisory Committee on Immunization Practices is addressing practical strategies for the annual vaccination of children as well as issues such as whether to administer two doses within the same season and reimbursement for vaccination. The formalization of a strong recommendation regarding influenza vaccination of children 6 to 23 months of age could be made in 2003. (1) The vaccination of children at least 6 months of age who have certain medical conditions (Table 2) continues to be recommended strongly. (1)

The recommended timing of influenza vaccination is from September through December. (1) Unlike 2001 and 2002, no delay in delivery or shortage of the vaccine is anticipated in 2003. Nevertheless, because of the uncertainty in predicting adequate vaccine supplies, the CDC's Advisory Committee on Immunization Practices continues to recommend that vaccination efforts in September and October focus on people at greatest risk for influenza-related complications and health care workers. (1) The individuals at greatest risk for influenza-related complications are listed in Table 2.

Chemoprophylaxis 

Chemoprophylactic drugs are not a substitute for vaccination. In certain situations, however, they can be helpful adjuncts in the prevention and control of influenza. Both rimantadine and amantadine are indicated for the chemoprophylaxis of influenza A infection but not influenza B infection. Both drugs can be up to 90% effective in preventing illness caused by influenza A infection. (29) When used for chemoprophylaxis, these antiviral agents prevent illness but permit subclinical infections that allow for the development of protective antibodies against circulating influenza A virus. Moreover, amantadine and rimantadine do not interfere with the antibody response to influenza vaccine. (30) Both agents have been studied in nursing home populations, in whom they have been incorporated into influenza outbreak control programs, and results show that amantadine and rimantadine can limit the spread of influenza in these LTCFs. (30)

Among the neuraminidase inhibitor antivirals zanamivir and oseltamivir, only oseltamivir has been approved for chemoprophylaxis. Compared with the adamantanes, experience with either neuraminidase inhibitor is limited. One 6-week study of oseltamivir chemoprophylaxis among nursing home residents reported a 92% reduction in influenza illness. (31) Community studies of healthy adults indicate that both drugs are approximately 80% effective in preventing febrile and laboratory-confirmed influenza illness. (32,33) The use of these agents also has been reported to prevent influenza among people administered chemoprophylaxis after a household member was diagnosed with influenza. (34) The use of zanamivir has not been reported to impair the immunologic response to influenza vaccine. (31) Furthermore, data are not available on the efficacy of any of the antiviral agents in preventing influenza among severely immunocompromised individuals. Decisions regarding the use of chemoprophylaxis either with or, less ideally, instead of the vaccine should be made only after considering a variety of issues, such as cost, compliance, potential side effects, and, of course, effectiveness. Chemoprophylaxis has been advocated in a variety of situations, as outlined in Table 3.

Management and Prevention of Influenza Outbreaks in Long-term Care Facilities

Background and Epidemiology. Each year, influenza wreaks havoc in LTCFs because patients in these institutions are particularly prone to infection by contagious pathogens. In the medical literature, influenza ranks among the most commonly reported causes of infectious disease outbreaks in nursing homes. (35) During the past decade, 16 outbreaks involving more than 1,000 residents in at least 20 facilities have been reported in the medical literature. (26) Influenza attack rates have been estimated to be as high as 20% among residents in nursing homes and assisted living facilities during years in which no epidemic occurs in the general population and as high as 70% in years in which epidemics and outbreaks have occurred. (15)

Although more common in the winter months, influenza outbreaks in nursing homes can occur at any time during the year. (35) Even in the absence of outbreaks, influenza probably occurs in endemic form on an annual basis in most facilities, perhaps because the clinical features are not specific and thus easily may go unrecognized. Influenza can arrive insidiously and persist for several months. Prospective surveillance studies for causes of respiratory tract infections in residents of LCTFs have clearly demonstrated that influenza A is a common respiratory tract isolate. (26)

Substantial morbidity and mortality among LTCF residents have been documented in outbreak investigations. Mortality rates in various outbreak reports during the past decade range from 5 to 55%. Moreover, in a meta-analysis of 19 observational studies of the impact of influenza in LTCFs, morbidity and mortality were considerably reduced among vaccinated individuals, suggesting that much of the illness in unvaccinated controls was due to influenza. (26)

Vaccination of at least 80% of residents at a given institution has correlated with decreased risk of an outbreak, but it is not fully protective. (35) Indeed, outbreaks have been reported even when resident vaccination rates at a given institution exceeded 90%. (37) Of particular interest, LTCF staff vaccination rates seem to be more important than resident vaccination rates in reducing mortality as a result of influenza. (35)

Causes and Routes of Spread. Most influenza outbreaks are caused by influenza A, but outbreaks caused by influenza B have been reported as well. (35) Influenza in the community at large enters LTCFs through staff and visitors who are infected. Thus, the regular appearance of influenza in LTCFs is not unexpected. Once inside the facility, the influenza virus spreads among residents, especially those of advanced age with multiple chronic illnesses and impairment in activities of daily living. Various factors have been reported to facilitate influenza infection and spread in LTCFs. Repeated exposure to infected staff and visitors, crowding, poor immunologic response to TIIV, and sometimes low vaccination rates in residents and/or staff of LCTFs are some of the reasons thought to be responsible for influenza outbreaks in these settings. (35)

Detection of an Outbreak. Some authorities have defined an outbreak of influenza as an overall attack rate of an influenza-like illness that involves at least 10% of the population in a single facility. Others have suggested that a single confirmed case of influenza in an LTCF is of epidemiologic significance. (35) Regardless of the definition used, proper management of influenza outbreaks starts with the prompt identification of influenza.

The classic signs and symptoms of influenza include the abrupt onset of fever, chills, rigors, malaise, headache, arthralgias, and myalgias. The clinical presentation of influenza infection may be modified with age or immune status. For example, elderly patients, especially those who are in a debilitated condition, may have complaints that are atypical. Comorbidities such as dementia or aphasia may render the patient unable to articulate complaints such as headache, sore throat, arthralgias, and myalgias to the health care provider. In these patients, anorexia, confusion, and changes in functional status may be the primary findings. Worsening respiratory status in patients with underlying chronic obstructive lung disease and congestive heart failure may be an unrecognized complication of influenza and may result in a higher morbidity and mortality rate. Indeed, atypical presentations are probably quite common in the elderly, and thus the clinician must maintain a high index of suspicion. (36)

Accurate diagnosis is essential. Confirmation studies should be available during the influenza season (ie, from December to March) by isolating influenza in culture or by performing a rapid assay for the detection of influenza viral antigens in clinical specimens with the use of direct fluorescent antibody or enzyme inmaunoassay methods. It has been suggested that if a rapid test is used to confirm influenza infection, the test ideally will be used to confirm influenza in more than one individual to increase the likelihood that a positive test result is a true-positive and not a false-positive result. (15) Identification of the exact species is important, because it could affect the selection of the chemoprophylactic agent administered. Identification of influenza B is of diagnostic and chemoprophylactic significance, because the amantadanes (ie, amantadine, rimantadine) are active only against influenza A. (26,36,37) Once a case has been confirmed to be influenza by laboratory testing, the rate of recovery of influenza virus of all patients with respiratory illnesses, regardless of symptom severity, can exceed 50% in the week after confirmation. Moreover, if the new illnesses are associated with fever, the rate of virus recovery has been estimated to be as high as 80%. (15)

Management of Outbreaks. After confirming an influenza outbreak in an LTCF, newly ill residents should be confined to their rooms for the duration of their symptoms. Alternatively, some LTCFs simply confine every resident, ill or well, during an outbreak. Many authorities also recommend reducing or even eliminating centralized recreation and other group activities until 72 hours after the onset of the last new respiratory illness. (15) Sick employees should be restricted from returning to work until they are well again. With regard to ill employees, a 4-day quarantine after the onset of symptoms has been suggested to be sufficient, because viral shedding in healthy adults only rarely occurs after the fourth day. (15) Many facilities also are closed to visitors during influenza outbreaks to further minimize the spread of illness. During an outbreak, prominent posting of reminder signs about avoiding close contact with other residents and staff and infection control measures such as regular handwashing and the use of masks may help to reduce the spread of influenza. (15) Avoiding the transfer of nursing and housekeeping staff between units or areas also may be helpful. (15)

Influenza treatment of at least the index case within an LTCF is controversial. Although the use of antivirals is usually recommended, few studies have assessed whether the early use of these agents after the onset of an influenza-like illness prevents illness, attenuates symptoms, shortens the duration of illness, or decreases mortality in the LTCF setting. To date, no randomized clinical trials of which I am aware have evaluated either the M2 channel inhibitors (ie, amantadine, rimantadine) or the neuraminidase inhibitors (NIs) oseltamivir and zanamivir for the treatment of elderly patients with influenza. A case control study of frail older residents of a nursing home during an influenza A outbreak found a nonsignificant trend toward reduction in the duration of clinical influenza symptoms in those patients who were treated with amantadine compared with the placebo group. (15) In addition, two meta-analyses of randomized clinical trials of zanamivir included post hoc subgroups of older community-dwelling patients. In the post hoc analysis of these 321 community-dwelling patients who were at least 64 years of age and/or had at least one chronic illness, a significant reduction was observed with regard to the duration of symptoms and influenza complications. (15) Treatment should therefore be individualized, bearing in mind that the M2 channel inhibitors, unlike the NIs, have activity only against influenza A. In addition, many health plans do not cover the cost of NIs, and the toxicity of each drug is probably increased in the elderly as compared with younger patients. (15) The usual recommended duration of treatment with either an M2 channel inhibitor or NI is approximately 5 days. (15)

Regardless of vaccination status, patients residing in institutions should be administered antiviral chemoprophylaxis with amantadine or rimantadine during an influenza A outbreak. The CDC as well as other authorities endorse this practice, even though clinical trial data could be strengthened. Chemoprophylaxis also should be considered in unvaccinated staff members who have contact with residents. (1,26,36,37) Of the four antiviral agents available, including the M2 channel-inhibiting agents amantadine and rimantadine and the neuraminidase inhibitors zanamivir and oseltamivir, only zanamivir lacks FDA approval for use as a chemoprophylactic drug. (15)

When the M2 channel inhibitors are used for chemoprophylaxis, a 14-day course seems to be sufficient, provided that it continues for at least 7 days after the onset of the last case of influenza. If a new case subsequently emerges, chemoprophylaxis with amantadine or rimantadine can be reinstated. Although more extended periods of use or the seasonal use of chemoprophylactic agents against influenza might offer the greatest reduction in infection transmission, problems related to drug toxicity as well as the emergence of resistant virus in addition to cost concerns make this option less attractive. Further information concerning proper dosing and the use of the various chemoprophylactic agents is included in the accompanying article by Myers. (38)

Prevention of Outbreaks. Clearly, vaccination of both patients and staff remains the cornerstone for the prevention of influenza in LTCFs including nursing homes. It is a safe, effective and cost-conscious intervention that is well supported by data in the medical literature. When chemoprophylaxis is used, it is primarily used as an adjunct to immunization and it is administered on a daily basis for defined periods of time. The Healthy People 2000 goal of vaccinating 60% of people aged 65 years and older was surpassed in 1997. However, the goal of a 90% vaccination rate in this population by 2010 could prove to be more challenging. (15) Figure 1 displays an algorithm for the detection and management of a suspected influenza outbreak in a LTCF. The antiviral drug dosage for each resident should be determined individually, taking into account a variety of issues such as renal function.

[FIGURE 1 OMITTED]

Table 1. Contraindications to influenza vaccination (a)

Absolute contraindications
  True anaphylactic hypersensitivity reaction to eggs

Relative contraindications
  Significant febrile illness
  Recent illness with Guillain-Barre syndrome
  Children younger than 6 months of age
  Women in the first trimester of pregnancy

(a) From, Bridges CB, Fukuda K, Uyeki TM, et al; Centers for Disease
Control and Prevention, Advisory Committee on Immunization Practices.
Prevention and control of influenza: Recommendations of the Advisory
Committee on Immunization Practices (ACIP). MMWR Recomm Rep 2002;51:10.
(1)

Table 2. Target populations for influenza vaccination (a)

People at increased risk for complications

  People at least 65 years of age

  Residents of nursing homes

  Adults and children with chronic cardiopulmonary disorders

  Adults and children with chronic metabolic diseases such as diabetes
    mellitus, renal dysfunction, and hemoglobinopathies

  Adults and children with immunosuppressed states caused by
    medication and/or infection with human immunodeficiency virus

  Children and adolescents undergoing long-term aspirin therapy

  Women who are in the second or third trimester of pregnancy during
    the influenza season

People 50-64 years of age

  People at least 50 years of age

People who can transmit influenza

  All health care personnel in hospital and outpatient care settings

  Any employee of a hospital, nursing home, long-term care facility, or
    assisted living facility who has contact with patients or residents

  Household members of people in high-risk groups, including any child
    at least 6 months of age

(a) From, Bridges CB, Fukuda K, Uyeki TM, et al; Centers for Disease
Control and Prevention, Advisory Committee on Immunization Practices.
Prevention and control of influenza: Recommendations of the Advisory
Committee on Immunization Practices (ACIP). MMWR Recomm Rep 2002;51:17.
(1)

Table 3. Indications for chemoprophylaxis (a)

People at high risk who are vaccinated for the first time after
    influenza activity has begun

  Chemoprophylaxis should be considered for approximately 2 weeks
    until immunity has developed

Children younger than 9 years of age being vaccinated with the
    trivalent inactivated influenza vaccine for the first time

  Chemoprophylaxis can require up to 6 weeks of treatment with an
    antiviral agent

Care providers of people at high risk who are not candidates for
    influenza vaccination

Elderly individuals exposed to an influenza outbreak, even if
    previously vaccinated

People with immune system deficiency

(a) From, Bridges CB, Fukuda K, Uyeki TM, et al; Centers for Disease
Control and Prevention, Advisory Committee on Immunization Practices.
Prevention and control of influenza: Recommendations of the Advisory
Committee on Immunization Practices (ACIP). MMWR Recomm Rep 2002;51:16.
(1)

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From the James H. Quillen VA Medical Center and the Department of Internal Medicine, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, TN.

No financial support was obtained for this manuscript. The authors of this manuscript do not have any financial, commerical, or proprietary interest in any drug, device, or equipment mentioned in this article. The views contained in this article do not necessarily reflect those of the Department of Veterans Affairs of the United States.

Reprint requests to Felix A. Sarubbi, MD, Department of Internal Medicine, James H. Quillen College of Medicine, East Tennessee State University, Box 70622, Johnson City, TN 37614. Email: [e-mail]

Accepted June 19, 2003.