Antiviral prophylaxis is indicated for influenza exposures that occur before (or less than 2 weeks after) vaccination with inactivated vaccine, or in years when circulating strains differ from those included in the vaccine. Antiviral drugs can also be used for treatment of patients who develop symptoms of influenza, regardless of vaccination status.
Please see Update: Influenza Resistance to Amantadine and Rimantadine

Last year influenza season began in October, peaked in December (both much earlier than usual), and was associated with severe disease, particularly in children. Much of the illness was due to a circulating influenza A H3N2 strain (Fujian type) that had drifted antigenically from the H3N2 strain in the vaccine. The vaccine for the 2004-05 influenza season includes A/Wyoming/3/2003 (H3N2), which is antigenically equivalent to the Fujian strain, A/New Caledonia/20/99 (H1N1), which is unchanged, and a new B strain, either B/Jiangsu/10/2003 or B/Jilin/20/2003, which are both antigenically equivalent to B/Shanghai/361/2002.

Patients planning to travel to other countries often ask physicians for advice about immunizations and prevention of diarrhea and malaria. More detailed advice for travelers is available from the Centers for Disease Control (CDC) at 877-FYI-TRIP (877-394-8747) or www.cdc.gov/travel. Recommendations for the treatment of parasitic diseases are available in the public reading room of The Medical Letter's web site.

Addendum: FluMist Storage: The storage requirements for FluMist, the intranasal live-attenuated influenza vaccine (Medical Letter 2003; 45:65) have changed. New data have shown that frost-free freezers are appropriate for storage for at least 3 months, without need for a freezer-box insert.

Unlike the last few years there is no early-season shortage of influenza vaccine. Immunization programs for all recommended individuals can proceed. There are 2 new influenza vaccine formulations available this year, FluMist, an intranasal vaccine and Fluzone, a pediatric formulation. Timing, indications, adverse effects, dosage and cost of the vaccines is discussed. The drugs that can be used for prophylaxis of influenza are also reviewed.

The centers for Disease Control and Prevention is anticipating a delay, but not a shortage, of influenza vaccine for the 2001-2002 season. Last year manufacturing problems led to a substantial delay in vaccine availability. This year's delay is being attributed, in part, to the dicontinuation of the Fluogen (King) brand of vaccine. The 2001-02 vaccine will include A/New Caledonia/20/99 (H1N1)-like, A/Moscow/10/99 (H3N2)-like, and B/Sichuan/379/99-like antigens.