Vaccines that protect against three strains of seasonal influenza considered most likely to strike the northern hemisphere this winter have received federal approval.
The Food and Drug Administration said Wednesday that four manufacturers licensed to sell their vaccines in the United States should have 100 million doses available for the 2006-2007 flu season. Barring any changes, that record number would end years of flu shot shortages and production delays.
The seasonal formulation includes one strain used in last year's vaccines and two new strains, the FDA said.
The vaccines do not protect against bird flu, which is caused by different strains of the virus. Scientists are developing vaccines that could protect against avian influenza.
Since different seasonal influenza strains crop up each year, experts tinker with the formulation to protect against those strains thought most likely to infect people in the upcoming flu season.
Each year, the flu hits between 5 percent and 20 percent of the U.S. population, according to the Centers for Disease Control and Prevention. More than 200,000 people are hospitalized and approximately 36,000 die. The elderly, children and people with certain chronic medical conditions face the greatest risk of serious complications.
The four vaccine manufacturers approved to sell flu vaccines in the United States are Chiron Corp., GlaxoSmithKline PLC, MedImmune Inc. and Sanofi Pasteur SA.