By Stephanie Stahl

PHILADELPHIA (CBS) — The flu season has arrived as cases have been reported in Pennsylvania, New Jersey and Delaware. Activity is low now, but doctors expect it to ramp up fast.

Everyone is being urged to get vaccinated now.

Allison Danks and her two daughters are getting their flu shots.

“I get my kids vaccinated every year just because it’s preventative,” Danks said.

When the flu arrives and how long the season lasts can vary, but activity usually starts increasing now. That’s why it’s recommended to get vaccinated before the end of October, if possible.

“That’s when the flu really starts to get bad, and even after the vaccine, it takes a few weeks to build immunity,” said Dr. Elissa Rubin, of Happy and Healthy Pediatrics.

The Centers for Disease Control and Prevention recommends everyone age six months and older to get the vaccine. Doctors are reminding patients not to believe the common misconception that the shot can give you the flu.

“It is impossible. It is a dead part of a virus in the vaccine and it cannot cause any illness,” Rubin said. “Most common side effects that we do see is feeling run down for the day because your body is building immunity. Sometimes you get a red, swollen arm at the site of injection.”

Guarding against influenza is important because it can be serious. Last flu season, as many as 43 million people got sick, 650,000 people were hospitalized and 61,000 died.

Danks says the benefits are worth a few tears.

“The flu shot doesn’t guarantee that they’re not gonna get it. But at least if they do end up getting it, hopefully they’ll have a milder case,” Danks said.

Danks says, as a parent, this is the best way to protect her children.

Stephanie Stahl