Now's the time to get your flu shot. The Centers for Disease Control and Prevention recommends people get the flu vaccine before the end of October.
The CDC says it takes at least two weeks for the antibodies that protect you against the flu to develop.
"School is back in session, people are now in close quarters, people are going back to work after summer vacations, so it's the prime environment for the flu virus to start spreading," said Dr. Megan Pearce, medical director for Trusted ER in Dallas.
If you happen to miss the recommended window, however, you should still get the shot. According to the CDC, the flu vaccine can still be beneficial if it's administered as late as January.
"So, if you haven't had it by December, go get it. If you haven't had it by January, go get it," Pearce said.
Pearce said only a select few might be told to have more than one dose or "booster" shot – namely, children 6 months of age up until age 8 years old.
Flue activity peaks between December and February but can last a late as May.