On Sept. 15, 2009, the U.S. Food and Drug Administration (FDA) approved four Influenza A (H1N1) 2009 Monovalent Vaccines for the active immunization of individuals against influenza disease caused by pandemic (H1N1) 2009 virus.

The four vaccines were made by CSL Limited, MedImmune, Novartis Vaccines, and Sanofi Pasteur. The FDA approval was based on data from multiple clinical trials examining the vaccines’ protective effects against influenza A (H1N1) in adults.