Comprehensive recommendations concerning the "flu" vaccine
courtesy of the Centers for Disease Control

               


 RECOMMENDATIONS FOR THE USE OF INFLUENZA VACCINE

Influenza vaccine is strongly recommended for any person 6 months of age who— because of age or underlying medical condition—is at increased risk for complications of influenza. Healthcare workers and others (including household members) in close contact with persons in high-risk groups should also be vaccinated. In addition, influenza vaccine may be administered to any person who wishes to reduce the chance of becoming infected with influenza. The trivalent influenza vaccine prepared for the 1996–97 season will include A/Texas/36/91-like (H1N1), A/Wuhan/359/95-like (H3N2), and B/Beijing/184/93-like hemagglutinin antigens. For both A/Wuhan/359/95-like and B/Beijing/184/93-like antigens, U.S. manufacturers will use the antigenically equiva-lent strains A/Nanchang/933/95 (H3N2) and B/Harbin/07/94 because of their growth properties. Guidelines for the use of vaccine among certain patient populations follow. Although the current influenza vaccine can contain one or more of the antigens administered in previous years, annual vaccination with the current vaccine is necessary because immunity declines in the year following vaccination. Because the 1996–97 vaccine differs from the 1995–96 vaccine, supplies of 1995–96 vaccine should not be administered to provide protection for the 1996–97 influenza season. Two doses administered at least 1 month apart may be required for satisfactory antibody responses among previously unvaccinated children <9 years of age; however, studies of vaccines similar to those being used currently have indicated little or no improvement in antibody response when a second dose is administered to adults during the same season. During recent decades, data on influenza vaccine immunogenicity and side effects have been obtained for intramuscularly administered vaccine. Because recent influenza vaccines have not been adequately evaluated when administered by other routes, the intramuscular route is recommended. Adults and older children should be vaccinated in the deltoid muscle and infants and young children in the thigh.

TARGET GROUPS FOR SPECIAL VACCINATION PROGRAMS

To maximize protection of high-risk persons, they and their close contacts should be targeted for organized vaccination programs.
Groups at Increased Risk for Influenza-Related Complications:

• Persons 65 years of age or older
• Residents of nursing homes and other chronic-care facilities that house persons of any age with chronic medical conditions
• Adults and children with chronic disorders of the pulmonary or cardiovascular systems, including children with asthma
• Adults and children who have required regular medical follow-up or hospitalization during the preceding year because of chronic metabolic diseases (including diabetes mellitus), renal dysfunction, hemoglobinopathies, or immunosuppression (including immunosuppression caused by medications)

The recommended site of vaccination is the deltoid muscle for adults and older children. The preferred site for infants and young children is the anterolateral aspect of the thigh. Two doses administered at least 1 month apart are recommended for children <9 years of age who are receiving influenza vaccine for the first time. · Children and teenagers (6 months–18 years of age) who are receiving long-term aspirin therapy and therefore might be at risk for developing Reye syndrome after influenza.

Groups that Can Transmit Influenza to Persons at High Risk Persons who are clinically or subclinically infected and who care for or live with members of high-risk groups can transmit influenza virus to them. Some persons at high risk (e.g., the elderly, transplant recipients, and persons with AIDS) can have a low antibody response to influenza vaccine. Efforts to protect these members of high-risk groups against influenza might be improved by reducing the likelihood of influenza exposure from their caregivers. Therefore, the following groups should be vaccinated:

• physicians, nurses, and other personnel in both hospital and outpatient-care settings;
• employees of nursing homes and chronic-care facilities who have contact with patients or residents;
• providers of home care to persons at high risk (e.g., visiting nurses and volunteer workers); and
• household members (including children) of persons in high-risk groups.

 

VACCINATION OF OTHER GROUPS

General Population

Physicians should administer influenza vaccine to any person who wishes to reduce the likelihood of becoming ill with influenza. Persons who provide essential community services should be considered for vaccination to minimize disruption of essential activities during influenza outbreaks. Students or other persons in institutional settings (e.g., those who reside in dormitories) should be encouraged to receive vaccine to minimize the disruption of routine activities during epidemics.

Pregnant Women

Influenza-associated excess mortality among pregnant women has not been documented except during the pandemics of 1918–19 and 1957–58. However, because death-certificate data often do not indicate whether a woman was pregnant at the time of death, studies are needed to assess the risks of influenza infection that are specifically associated with pregnancy. Case reports and limited studies suggest that women in the third trimester of pregnancy and early puerperium, including those women without underlying risk factors, might be at increased risk for serious complications following influenza infection. Certain pregnancy-related physiologic changes may increase the risk for such complications; as pregnancy progresses, cardiac output, heart rate, oxygen consumption, and stroke volume increase while lung capacity decreases. Immunologic changes during pregnancy also may increase the risk for severe influenza illness. Health-care workers who provide care for pregnant women should consider administering influenza vaccine to all women who would be in the third trimester of pregnancy or early puerperium during the influenza season. Pregnant women who have medical conditions that increase their risk for complications from influenza should be vaccinated before the influenza season, regardless of the stage of pregnancy. Although definitive studies have not been conducted, influenza vaccination is considered safe at any stage of pregnancy.

Persons Infected with HIV

Limited information exists regarding the frequency and severity of influenza illness among HIV-infected persons, but reports suggest that symptoms might be prolonged and the risk for complications increased for some HIV-infected persons. Influenza vaccine has produced protective antibody titers against influenza in vaccinated HIV-infected persons who have minimal AIDS-related symptoms and high CD4+ T-lymphocyte cell counts. In patients who have advanced HIV disease and low CD4+ T-lymphocyte cell counts, however, influenza vaccine may not induce protective antibody titers; a second dose of vaccine does not improve the immune response for these persons. Recent studies have examined the effect of influenza vaccination on replication of HIV type 1 (HIV-1). Although some studies have demonstrated a transient (i.e., 2- to 4-week) increase in replication of HIV-1 in the plasma or peripheral blood mononuclear cells of HIV-infected persons after vaccine administration, other studies using similar laboratory techniques have not indicated any substantial increase in replication. Deterioration of CD4+ T-lymphocyte cell counts and progression of clinical HIV disease have not been demonstrated among HIV-infected persons who receive vaccine. Because influenza can result in serious illness and complications and because influenza vaccination may result in protective antibody titers, vaccination will benefit many HIV-infected patients.

Foreign Travelers

The risk for exposure to influenza during foreign travel varies, depending on season and destination. In the tropics, influenza can occur throughout the year; in the Southern Hemisphere, most activity occurs from April through September. Because of the short incubation period for influenza, exposure to the virus during travel can result in clinical illness that begins while traveling, an inconvenience or potential danger, especially for persons at increased risk for complications. Persons preparing to travel to the tropics at any time of year or to the Southern Hemisphere from April through September should review their influenza vaccination histories. If they were not vaccinated the previous fall or winter, they should consider influenza vaccination before travel. Persons in high-risk categories should be especially encouraged to receive the most current vaccine. Persons at high risk who received the previous season’s vaccine before travel should be revaccinated in the fall or winter with the current vaccine.

PERSONS WHO SHOULD NOT BE VACCINATED

Inactivated influenza vaccine should not be administered to persons known to have anaphylactic hypersensitivity to eggs or to other components of the influenza vaccine without first consulting a physician (see Side Effects and Adverse Reactions). Use of an antiviral agent (i.e., amantadine or rimantadine) is an option for prevention of influenza A in such persons. However, persons who have a history of anaphylactic hypersensitivity to vaccine components but who are also at high risk for complications of influenza can benefit from vaccine after appropriate allergy evaluation and desensitization. Specific information about vaccine components can be found in package inserts for each manufacturer. Adults with acute febrile illness usually should not be vaccinated until their symptoms have abated. However, minor illnesses with or without fever should not contraindicate the use of influenza vaccine, particularly among children with mild upper respiratory tract infection or allergic rhinitis.


SIDE EFFECTS AND ADVERSE REACTIONS

Because influenza vaccine contains only noninfectious viruses, it cannot cause influenza. Respiratory disease after vaccination represents coincidental illness unrelated to influenza vaccination. The most frequent side effect of vaccination reported by fewer than one third of vaccinees is soreness at the vaccination site that lasts for up to 2 days. In addition, two types of systemic reactions have occurred:

• Fever, malaise, myalgia, and other systemic symptoms occur infrequently and most often affect persons who have had no exposure to the influenza virus antigens in the vaccine (e.g., young children). These reactions begin 6–12 hours after vaccination and can persist for 1 or 2 days;
• Immediate—presumably allergic—reactions (e.g., hives, angioedema, allergic asthma, and systemic anaphylaxis) occur rarely after influenza vaccination. These reactions probably result from hypersensitivity to some vaccine component; the majority of reactions are most likely related to residual egg protein. Although current influenza vaccines contain only a small quantity of egg protein, this protein can induce immediate hypersensitivity reactions among persons who have severe egg allergy. Persons who have developed hives, have had swelling of the lips or tongue, or have experienced acute respiratory distress or collapse after eating eggs should consult a physician for appropriate evaluation to help determine if vaccine should be administered. Persons with documented immunoglobulin E (IgE)-mediated hypersensitivity to eggs—including those who have had occupational asthma or other allergic responses due to exposure to egg protein—might also be at increased risk for reactions from influenza vaccine, and similar consultation should be considered. The protocol for influenza vaccination developed by Murphy and Strunk may be considered for patients who have egg allergies and medical conditions that place them at increased risk for influenzaassociated complications (Murphy and Strunk, 1985).
• Hypersensitivity reactions to any vaccine component can occur.
  

SIMULTANEOUS ADMINISTRATION OF OTHER VACCINES, INCLUDING CHILDHOOD VACCINES

The target groups for influenza and pneumococcal vaccination overlap considerably. For persons at high risk who have not previously been vaccinated with pneumococcal vaccine, health-care providers should strongly consider administering both pneumococcal and influenza vaccines concurrently. Both vaccines can be administered at the same time at different sites without increasing side effects. However, influenza vaccine is administered each year, whereas pneumococcal vaccine is not. Children at high risk for influenza-related complications can receive influenza vaccine at the same time they receive other routine vaccinations, including pertussis vaccine (DTP or DTaP). Because influenza vaccine can cause fever when administered toyoung children, DTaP might be preferable in those children 15 months of age who are receiving the fourth or fifth dose of pertussis vaccine. DTaP is not licensed for the initial three-dose series of pertussis vaccine.

TIMING OF INFLUENZA VACCINATION ACTIVITIES

Beginning each September (when vaccine for the upcoming influenza season becomes available) persons at high risk who are seen by healthcare providers for routine care or as a result of hospitalization should be offered influenza vaccine. Opportunities to vaccinate persons at high risk for complications of influenza should not be missed. In previously published recommendations, the optimal time for organized vaccination campaigns for persons in high-risk groups was defined as the period from mid-October through mid-November. This period has been extended to include the first 2 weeks in October. In the United States, influenza activity generally peaks between late December and early March. High levels of influenza activity infrequently occur in the contiguous 48 states before December. Administering vaccine too far in advance of the influenza season should be avoided in facilities such as nursing homes, because antibody levels might begin to decline within a few months of vaccination. Vaccination programs can be undertaken as soon as current vaccine is available if regional influenza activity is expected to begin earlier than December. Children <9 years of age who have not been vaccinated previously should receive two doses of vaccine at least 1 month apart to maximize the likelihood of a satisfactory antibody response to all three vaccine antigens. The second dose should be administered before December, if possible. Vaccine should be offered to both children and adults up to and even after influenza virus activity is documented in a community.