Dr. Lisa Fitzpatrick answers questions about the flu and the flu vaccine.
Viruses can change. What we call mutate. The flu is a virus that changes from year to year. And because of that it’s necessary to produce a new vaccine each year.
Scientists who are very informed about the flu and understand the genetics of the flu virus, they make a decision about what the most likely flu strain will be and that’s how they determine what the flu shot will be for that year.