2008 Prevention of Influenza Guidelines: Changes to Consider

Abstract and Commentary

By Mary-Louise Scully, MD, Dr. Scully is Director, Travel and Tropical Medicine Center, Sansum Clinic, Santa Barbara, CA.

Dr. Scully reports no financial relationships relevant to this field of study.

This article originally appeared in the October 2008 issue of Travel Medicine Advisor. It was edited by Frank Bia, MD, and peer reviewed by Philip Fischer, MD. Dr. Bia is Professor of Geographic and Laboratory Medicine., Co-Director, Tropical Medicine and International Travelers' Clinc, Yale University School of Medicine, and Dr. Fischer is Professor of Pediatrics, Department of Pediatrics and Adolescent Medicine, Mayo Clinic, Rochester, MN. Dr. Bia is a consultant for Pfizer and Sanofi Pasteur, and receives funds from Johnson & Johnson, and Dr. Fischer reports no financial relationships relevant to this field of study.

Synopsis: The new influenza guidelines now recommend annual vaccination of children ages 5-18 years in addition to the previous recommendation of children ages 6 months to 5 years. To meet the anticipated vaccine demand, the FDA has released 113 lots of the 2008-2009 Northern Hemisphere influenza vaccine produced by 6 different manufacturers.

Source: Fiore AE, et al. Prevention and control of influenza: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2008. MMWR 2008;57:1-60.

This report updates the 2007 recommendations by the CDC Advisory Committee on Immunization Practices (ACIP) with regard to the use of influenza vaccine and antiviral agents. The important changes include: 1) a new recommendation that annual vaccination be administered to all children ages 5-18 years beginning in the 2008-2009 influenza season, if feasible, but no later than the 2009-2010 season; 2) a recommendation that annual vaccination of all children ages 6-59 months continue to be a primary focus of vaccination efforts since these children are at higher risk of influenza complications 3) a new recommendation that either trivalent inactivated influenza vaccine (TIV) or live, attenuated influenza vaccine (LAIV) be used when vaccinating healthy persons ages 2-49 years (the previous recommendation was to administer LAIV to persons only between 5-49 years); and 4) a recommendation that vaccines containing the 2008-2009 trivalent vaccine virus strains A/Brisbane/59/2007 (H1N1)-like, A/Brisbane/10/2007 (H3N2)-like, and B/Florida/4/2006-like antigens be used.

The recommendation remains that children ages 6 months to 8 years should receive two doses of influenza vaccine (doses separated by ≥ 4 weeks) if they have not been vaccinated previously at any time with either LAIV or TIV because two doses are needed for protection in these children. Two doses also should be given to children ages 6 months to 8 years who received only one dose in their first year of vaccination. In children < 5 years with asthma or reactive airways disease, LAIV should be avoided. Since LAIV is a live, attenuated vaccine, it is contraindicated in immunosuppressed individuals. Patients with a history of hypersensitivity to eggs and a history of Guillain-Barré after influenza vaccination should not be vaccinated with either LAIV or TIV.

Annual recommendations for adults have not changed, and essentially encourage vaccination for any adult who wants to reduce the risk of becoming ill with influenza or of transmitting influenza to others. Persons older than 50 years; pregnant women; patients with chronic pulmonary, cardiac, or renal conditions; diabetic patients; immunosuppressed patients; nursing home patients; health care workers; and caregivers of young children remain a focus of adult vaccination programs.

Other inactivated vaccines can be administered simultaneously with either TIV or LAIV. Among children 12-15 months of age, the concurrent use of LAIV with measles, mumps, rubella (MMR) alone, and MMR and varicella vaccine has been examined, and no interference in immune response was observed. In addition, based on available safety and immunogenicity data, it is acceptable to administer TIV with zoster vaccine for adults older than 50 years.

As resistance to both amantadine and rimantidine has increased rapidly in the past several years, oseltamivir and zanamivir remain the only antiviral medications recommended for influenza treatment or prophylaxis in the United States. Unfortunately, in 2007-2008, increased resistance to oseltamivir was reported in many countries among influenza A (H1N1) viruses. In the United States, during the 2007-2008 influenza season, about 10% of influenza A (H1N1) viruses were found resistant to oseltamivir, but none of the influenza A (H3N2) or influenza B viruses were found to be resistant (overall percentage of influenza A and B viruses resistant to oseltamivir was < 5%). However, antiviral recommendations may change during the 2008-2009 season, and clinicians can keep up to date with information available on the CDC's web site (http://www.cdc.gov/flu/professionals/antivirals/index.htm).

Commentary

The influenza vaccine supply is projected to be abundant this year, with 113 lots of Northern Hemisphere vaccine released by the FDA to meet the expected demand for implementation of the new pediatric recommendations. In addition, the vaccine antigens have been changed to reflect the predominant strains of last year's season.

Success ultimately will depend upon both health care providers' endorsement of the implementation and, even more, the endorsement from parents and caregivers of children. The LAIV and the single-dose vials or syringes of TIV are considered thimerosal-free (0 or < 1.0 mcg per 0.5 mL dose) and, therefore, preferred for infants and pregnant women. All multi-dose vials still contain about 25 m mercury per 0.5 mL dose. In 2001, the US Public Health Service and other organizations recommended that efforts be made to remove or reduce the thimerosal content from vaccines as part of an overall plan to reduce mercury exposures from all sources.1 Each year, it is expected that the number of influenza vaccines that do not contain thimerosal will continue to grow.

Respiratory infections are second after gastrointestinal infections as a cause of illness in travelers, and influenza accounts for 5%-6% of respiratory illness reported in travelers.2 Influenza virus is spread by direct contact or aerosol (fine droplet), and the traveler's world of crowded airports, buses, museums, and churches poses a perfect setting for influenza transmission. Outbreaks have occurred on cruise ships, an increasingly favored way of traveling for many, and which are especially conducive to influenza transmission.3 Moreover, influenza circulates at low levels year round in the tropics — a frequent destination of travelers and cruise ships. Cruise ships often have a mixture of passengers and crew from both hemispheres and, although the available vaccine in the country of departure may not be matched optimally for the circulating strains in the opposite hemisphere, it is always preferable to vaccinate than to let the individual travel without any vaccine protection at all.4

References

  1. CDC. Summary of the Joint Statement on Thimerosal in Vaccines. MMWR. 2000;49:622-631.
  2. Leder K, et al. Respiratory tract infections in travelers: A review of the GeoSentinel Surveillance Network. Clin Infect Dis. 2003;36:399-406.
  3. Miller JM, et al. Cruise ships: High-risk passengers and the global spread of new influenza viruses. Clin Infect Dis. 2000:31:433-438.
  4. Freedman DO, Leder K. Influenza: changing approaches to prevention and treatment in travelers. J Travel Med. 2005; 12:36-44.