Prevention and Control of Influenza

Recommendations of the Advisory Committee on Immunization Practices (ACIP)

Primary Changes and Updates in the Recommendations

The 2002 recommendations include five principal changes or updates, as follows:

1. The optimal time to receive influenza vaccine is during October and November. However, because of vaccine distribution delays during the past 2 years, ACIP recommends that vaccination efforts in October focus on persons at greatest risk for influenza-related complications and health-care workers and that vaccination of other groups begin in November.
2. Vaccination efforts for all groups should continue into December and later, for as long as vaccine is available.
3. Because young, otherwise healthy children are at increased risk for influenza-related hospitalization, influenza vaccination of healthy children aged 6--23 months is encouraged when feasible. Vaccination of children aged >6 months who have certain medical conditions continues to be strongly recommended.
4. The 2002--2004 trivalent vaccine virus strains are A/Moscow/10/99 (H3N2)-like, A/New Caledonia/20/99 (H1N1)-like, and B/Hong Kong/330/2001-like strains.
5. A limited amount of influenza vaccine with reduced thimerosal content will be available for the 2002--2004 influenza season.

Timing of Organized Vaccination Campaigns

Persons planning substantial organized vaccination campaigns should consider scheduling these events after mid-October because the availability of vaccine in any location cannot be ensured consistently in the early fall. Scheduling campaigns after mid-October will minimize the need for cancellations because vaccine is unavailable. Campaigns conducted before November should focus efforts on vaccination of persons at high risk, health-care workers, and household contacts of persons at high-risk to the extent feasible.

Vaccination in December and Later

After November, certain persons who should or want to receive influenza vaccine remain unvaccinated. In addition, substantial amounts of vaccine have remained unused during the past two influenza seasons. To improve vaccine coverage and use, chiefly among persons at high risk and health-care workers, influenza vaccine should continue to be offered in December and throughout the influenza season as long as vaccine supplies are available, even after influenza activity has been documented in the community. In the United States, seasonal influenza activity can begin to increase as early as November or December, but influenza activity has not reached peak levels in the majority of recent seasons until late December through early March. Therefore, although the timing of influenza activity can vary by region, vaccine administered after November is likely to be beneficial in the majority of influenza seasons. Adults develop peak antibody protection against influenza infection 2 weeks after vaccination.