Flu viruses usually cause the most illness
during the colder months of the year. In the United States, flu season is from October
to May. Most cases happen from late December to early March.
It's best to get the flu vaccine
early in flu season, ideally by the end of October. That way, the body has time to
make antibodies that protect it from the flu.
What if you aren't vaccinated by then? Getting the vaccine later is better than
not getting it at all. It's still flu season well into spring — even then it's
not too late for you and your family to get the flu vaccine.