July 3, 2007 — The Centers for Disease Control and Prevention (CDC) have updated their 2006 recommendations for use of the influenza vaccine and antiviral agents. The revised guidelines ("Prevention and Control of Influenza: Recommendations of the Advisory Committee on Immunization Practices [ACIP], 2007") are published in the June 29 Early Release issue of the Morbidity and Mortality Weekly Report.
"Influenza vaccination is the most effective method for preventing influenza virus infection and its potentially severe complications," write Anthony E. Fiore, MD, from the Influenza Division, National Center for Immunization and Respiratory Diseases, and colleagues from the CDC. "Influenza immunization efforts are focused primarily on providing vaccination to persons at risk for influenza complications and to contacts of these persons.... Antiviral medications are an adjunct to vaccination and are effective when administered as treatment and when used for chemoprophylaxis after an exposure to influenza virus."
In updating their recommendations regarding influenza, the working group considered vaccine efficacy, safety, and coverage in groups recommended for vaccination as well as feasibility, cost-effectiveness, and anticipated vaccine supply. They consulted vaccinologists, epidemiologists, vaccine manufacturers, and state and local immunization program representatives. The CDC's Influenza Division provided influenza surveillance and antiviral resistance data, and the Vaccines and Related Biological Products Advisory Committee of the US Food and Drug Administration selected the viral strains to be used in the annual trivalent influenza vaccines.
Since 2006, the guidelines have not changed for groups of persons for whom vaccination are recommended and for the antiviral medications recommended for chemoprophylaxis or treatment.
Specifically, the guidelines recommend annual influenza vaccination for all persons, including school-aged children, who want to reduce the risk of becoming ill with influenza or of transmitting influenza to others; all children aged 6 months to 4 years; all adults aged 50 years or older; individuals aged 6 months to 18 years at increased risk for Reye's syndrome because of long-term treatment with aspirin; women who will be pregnant during the influenza season; persons with chronic pulmonary (including asthma), cardiovascular (excluding hypertension), renal, hepatic, hematologic, or metabolic disorders (including diabetes); immunosuppressed persons; those with any condition that can compromise respiratory function; residents of nursing homes and other chronic care facilities; healthcare personnel; healthy household contacts and caregivers of children younger than 5 years and adults aged 50 years or older (especially contacts of infants younger than 6 months); and persons with medical conditions increasing their risk for severe complications from influenza.
"Estimated vaccination coverage remains < 50% among certain groups for whom routine annual vaccination is recommended, including young children and adults with risk factors for influenza complications, health-care personnel, and pregnant women," the authors write. "Strategies to improve vaccination coverage, including use of reminder/recall systems and standing orders programs, should be implemented or expanded."
In the United States, the only antiviral medications currently recommended for use against influenza are oseltamivir and zanamivir; resistance to these drugs remains rare. Until evidence of susceptibility to amantadine or rimantadine has been reestablished for circulating influenza A viruses, these agents should not be used in the United States to treat or prevent influenza.
Oseltamivir is approved for treatment of persons older than 1 year, whereas zanamivir is approved for use in persons aged 7 years or older. For chemoprophylaxis of influenza, oseltamivir is licensed for use in persons aged 1 year or older, and zanamivir is licensed for use in persons aged 5 years or older. Both of these agents are neuraminidase inhibitors with activity against both influenza A and B viruses.
Specific changes and updates in the 2007 guidelines are as follows:
The guidelines highlight the importance of giving 2 doses of vaccine to all children aged 6 months to 8 years if they have not been vaccinated previously at any time with either live attenuated influenza vaccine (doses separated by 6 weeks or more) or with trivalent inactivated influenza vaccine (doses separated by 4 weeks or more), with single annual doses in the following years.
Children aged 6 months to 8 years who received only 1 dose in their first year of vaccination should receive 2 doses in the following year and single annual doses in subsequent years.
The guidelines reinforce an earlier recommendation that all persons, including school-aged children, who want to reduce the risk of contracting influenza or of transmitting influenza to others should be vaccinated.
Immunization providers should offer influenza vaccine and schedule immunization clinics throughout the influenza season.
Healthcare facilities should consider the level of vaccination coverage among healthcare personnel to be 1 measure of a patient safety quality program and should implement policies to encourage vaccination of healthcare personnel, such as obtaining signed statements from healthcare personnel who refuse influenza vaccination.
Vaccination against influenza should use the 2007 to 2008 trivalent vaccine virus strains A/Solomon Islands/3/2006 (H1N1)-like (new for this season), A/Wisconsin/67/2005 (H3N2)-like, and B/Malaysia/2506/2004-like antigens, because they are representative of influenza viruses that are anticipated to circulate in the United States during the 2007 to 2008 influenza season and because they have favorable growth properties in eggs.
Either trivalent influenza vaccine or live attenuated influenza vaccine can be used to lower the risk for influenza virus infection or its sequelae. Healthy, nonpregnant persons aged 5 to 49 years can receive either vaccine; trivalent influenza vaccine is approved by the US Food and Drug Administration for persons aged 6 months or older, including those with high-risk conditions, whereas live attenuated influenza vaccine is approved by the US Food and Drug Administration for use only in healthy persons aged 5 to 49 years. All children aged older than 6 months to 8 years who have not previously been vaccinated with either live attenuated influenza vaccine or trivalent influenza vaccine should receive 2 doses of age-appropriate vaccine in the same season and a single dose during subsequent seasons.
The authors note that further updates or supplements to these recommendations, such as expanded age or risk group indications for currently licensed vaccines, may be needed and that immunization providers should heed new announcements regarding updates and should consult the CDC influenza Web site periodically for additional information.
"Although influenza vaccination levels increased substantially during the 1990s, little progress has been made toward achieving national health objectives, and further improvements in vaccine coverage levels are needed," the authors conclude. "Strategies to improve vaccination levels, including using reminder/recall systems and standing orders programs, should be implemented whenever feasible. Vaccination coverage can be increased by administering vaccine before and during the influenza season to persons during hospitalizations or routine health-care visits."
MMWR Morb Mortal Wkly Rep. Published online June 29, 2007.2007;56:1-54.
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