Currently circulating influenza virus is almost universally pandemic 2009 influenza A H1N1, but seasonal influenza strains could also appear soon. Antiviral drugs are an important adjunct to influenza vaccination for treatment and chemoprophylaxis of both pandemic and seasonal influenza. They may, however, interfere with the efficacy of FluMist, the live-attenuated intranasal vaccine, if they are administered within 48 hours before or <2 weeks after FluMist administration. Inactivated vaccines are not affected by antiviral drug therapy.

Patients planning to travel to other countries often ask physicians for information about appropriate vaccines and prevention of diarrhea and malaria. Guidelines are also available from the Infectious Diseases Society of America (IDSA).

The FDA has licensed 4 new monovalent vaccines for prevention of respiratory illness caused by a new influenza A H1N1 virus that appears to be derived from a swine strain. The 5th vaccine should be licensed soon. All of these vaccines are expected to become available in October. An intranasal formulation is expected in the first week of October.