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Influenza or the flu, has been associated with an average of more than 200,000 hospitalizations and 36,000 deaths between the 1990 and 1999 according to the Centers for Disease Control and Preventions (CDC). The flu is a contagious respiratory infection caused by the influenza virus A or B which affects between five to 20 percent of the population every winter. The influenza virus is one of the most changeable of viruses. For this reason, a new flu vaccine must be produced each year to combat that year's prevalent strains. Currently, influenza vaccine manufacturers are projecting that approximately 100 million doses of influenza vaccine will be available in the United States for the 2006--07 influenza season, an amount that is approximately 16% more doses than were available for the 2005--06 season. An additional 15 million--20 million doses might be available if a new vaccine is licensed in 2006. (Information about the status of licensure of new vaccines is available in Red Book Online: Status of Licensure and Recommendations for New Vaccines .)
The CDCs' Advisory Committee on Immunization Practices (ACIP) states that the effectiveness of the vaccine is dependent on the age and immunocompetence of the recipient. The 2006-2007 annual influenza vaccination is now recommended for the following groups:
- persons at high risk for influenza-related complications and severe disease, including
--- children aged 6--59 months,
--- pregnant women,
--- persons aged >50 years,
--- persons of any age with certain chronic medical conditions; and
- persons who live with or care for persons at high risk, including
--- household contacts who have frequent contact with persons at high risk and who can transmit influenza to those persons at high risk and
--- health-care workers.
The 2006 recommendations include six principal changes or updates:
- ACIP recommends that healthy children aged 24--59 months and their household contacts and out-of-home caregivers be vaccinated against influenza (see Target Groups for Vaccination). This change extends the recommendations for vaccination of children so that all children aged 6--<59 months receive annual vaccination.
- ACIP emphasizes that all children aged 6 months--<9 years who have not been previously vaccinated at any time with either live, attenuated influenza vaccine (LAIV) or trivalent inactivated influenza vaccine (TIV) should receive 2 doses of vaccine. Those children aged 6 months--<9 years who receive TIV should have a booster dose of TIV administered >1 month after the initial dose, before the onset of influenza season, if possible. Those children aged 5--<9 years who receive LAIV should have a second dose of LAIV 6--10 weeks after the initial dose, before the influenza season, if possible. If a child aged 6 months--<9 years received influenza vaccine for the first time during a previous season but did not receive a second dose of vaccine within the same season, only 1 dose of vaccine should be administered this season (see Efficacy and Effectiveness of Inactivated Influenza Vaccine, Children; TIV Dosage; and LAIV Dosage and Administration).
- To ensure optimal use of available doses of influenza vaccine, projected to be approximately 100 million doses, health-care providers, those planning organized campaigns, and state and local public health agencies should 1) develop plans for expanding outreach and infrastructure to vaccinate more persons than during the previous year and 2) develop contingency plans for the timing and prioritization of administering influenza vaccine, if the supply of vaccine is delayed and/or reduced because of the complexity of the production process (see Influenza Vaccine Supply and Timing of Annual Influenza Vaccination).
- ACIP emphasizes that influenza vaccine should continue to be offered throughout the influenza season even after influenza activity has been documented in a community. In addition, ACIP encourages all community vaccinators and public health agencies to schedule clinics that serve target groups and to help extend the routine vaccination season by offering at least one vaccination clinic in December (see Influenza Vaccine Supply and Timing of Annual Influenza Vaccination).
- ACIP recommends that neither amantadine nor rimantadine be used for the treatment or chemoprophylaxis of influenza A in the United States because of recent data indicating widespread resistance of influenza virus to these medications. Until susceptibility to adamantanes has been re-established among circulating influenza A viruses, oseltamivir or zanamivir may be prescribed if antiviral treatment or chemoprophylaxis of influenza is indicated (see Recommendations for Using Antiviral Agents for Influenza).
- The 2006--07 trivalent vaccine virus strains are A/New Caledonia/20/1999 (H1N1)-like, A/Wisconsin/67/2005 (H3N2)-like, and B/Malaysia/2506/2004-like antigens. For the A/Wisconsin/67/2005 (H3N2)-like antigen, manufacturers may use the antigenically equivalent A/Hiroshima/52/2005 virus; for the B/Malaysia/2506/2004-like antigen, manufacturers may use the antigenically equivalent B/Ohio/1/2005 virus (see Influenza Vaccine Composition).
Month of peak influenza activity* during 30 influenza seasons—United States, 1976–2006 |
| |
Month |
|
Nov |
Dec |
Jan |
Feb |
Mar |
Apr |
May |
| No. (%) of years with peak influenza activity |
1 (3) |
4 (13) |
6 (20) |
13 (43) |
4 (13) |
1 (3) |
1 (3) |
|
* The peak week of activity was defined as the week with the greatest percentage of respiratory specimens testing positive for influenza on the basis of a 3-week moving average. Laboratory data provided by U.S. World Health Organization Collaborating Centers (CDC, unpublished data, 1976-2006). |
Avian Influenza
The emergence of avian flu or H5N1, which is caused by an influenza A virus and occurs naturally in birds, in human cases throughout Asia, the Middle East and Eastern Europe has some concerned about the potential effects. More than 200 confirmed cases of human infection with avian influenza A (H5N1) viruses have been reported since 2004. The rationale for the use of additional precautions for avian influenza as compared with human influenza include the following:
- The risk of serious disease and increased mortality from highly pathogenic avian influenza may be significantly higher than from infection by human influenza viruses.
- Each human infection represents an important opportunity for avian influenza to further adapt to humans and gain the ability to transmit more easily among people.
- Although rare, human-to-human transmission of avian influenza may be associated with the possible emergence of a pandemic strain.
The Consumer Federation of America has a new brochure available, "A Consumer Guide to Avian Influenza." |
