From May through September 2001, influenza A(H1N1), A(H3N2), and B viruses have continued to circulate worldwide and the majority of viruses are well matched to the components of the 2001-02 influenza vaccine. The optimal time period for persons at increased risk for influenza-related complications to receive an annual flu shot is October and November.

The following recommendations address an anticipated delay in influenza vaccine delivery. Healthcare providers should: 1) target vaccine available in September and October to persons at increased risk for influenza complications and to health-care workers and, 2) beginning in November, also offer vaccine to contacts of high-risk persons, healthy persons aged 50-64 years, and any others who want to reduce their risk for influenza, and 3) continue vaccinating patients in December and throughout the flu season as long as vaccine is available.