Sanofi Pasteur, the vaccines division of Sanofi (NYSE:SNY), has won FDA approval for the first and only four-strain influenza vaccine for patients as young as 6 months of age.

According to the World Health Organization, during annual influenza outbreaks, 5% to 15% of the population is likely to suffer upper respiratory tract infections. Hospitalization and death mainly occur in high-risk groups (the elderly and chronically ill). These annual epidemics are thought to result in between three and five million cases of severe illness, and between 250,000 and 500,000 deaths annually around the world.

For the past 35 years, influenza vaccines have been formulated to protect against only three strains of influenza virus: type A (H1N1), type A (H3N2), and one form of type B. However, since the 2001-2002 season, two influenza B types (Victoria and Yamagata) have caused disease outbreaks -- only one of which is dominant in a given year -- making it difficult to predict which B strain to include in the vaccine for the upcoming season. In 50% of the past 12 flu seasons, the dominant circulating B strain came from the B-lineage not selected for inclusion. Even when the correct B lineage strain is selected, some disease will be caused by the B lineage omitted, reducing overall effectiveness of preventive vaccination. 

Sanofi's new vaccine covers both A strains and both B strains, eliminating the uncertainty of prediction.

The vaccine will be available to health-care providers in the U.S. for the 2013-2014 influenza season.

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