How are the viruses for the flu vaccine selected?
Each year, flu viruses are collected in labs around the world. In the United States, the World Health Organization (WHO) reference lab at the Centers for Disease Control and Prevention (CDC) performs detailed testing on select viruses from these labs, and study how well antibodies made to the current vaccine react to new and already circulating viruses. An advisory committee of the U.S. Food and Drug Administration (FDA) is presented with the data, and three viruses are selected to go into flu vaccines for the following season.
