It's flu shot time, and this year the U.S. Centers for Disease Control and Prevention says children ages 5 to 18 should be immunized. That is in addition to other groups: children ages 6 months to 5 years; people 50 and older; and adults at risk, such as those with chronic diseases and pregnant women.

Anyone who wants to be protected can get a shot, the CDC says. As flu shot clinics rev up in the Madison area, the Wisconsin State Journal answers questions for people who might wonder if and when they should roll up their sleeves:

Why are children ages 5 to 18 supposed to get flu shots?

Unlike the very young or the elderly, school-age children have a low risk of dying or requiring hospitalization from the flu, health officials say.

But school-age children are perhaps the most likely to get the flu and spread it to others. "The best way to protect the others is to keep the kids who are in school from getting sick," Murwin said.

Also, the flu can make children miserable and keep them out of school, forcing parents to take time off work, said Dr. Greg DeMuri, a pediatrician at UW Health. "There's a big social cost to influenza," he said.

Teens or preteens are being told to get other shots, against pertussis (whooping cough), meningitis and HPV (which can cause cervical cancer). That's on top of many childhood shots. Is there a cumulative risk to these vaccines?

Some experts — such as Dr. Robert Sears, author of "The Vaccine Book" — propose an alternative vaccine schedule because of this concern. But most doctors dismiss it, saying vaccines contain relatively few antibodies.

"The human body is inundated by foreign antibodies daily — when you brush your teeth or go to the bathroom," said Dr. Greg DeMuri, a pediatrician at UW Health.  "There's no evidence that exposing patients to more vaccines is harmful."

Is thimerosal, the mercury-containing preservative some claim is linked to autism, in flu shots? Is it harmful?

There is no proof of a link between thimerosal and autism or other conditions, and flu shots are safe, the CDC says.

Small amounts of the preservative remain in most flu shots (multi-dose vials), but thimerosal-free vaccine is available (in single-dose vials and pre-filled syringes) Ask your doctor or clinic if you prefer that.

Who should consider FluMist, the nasal spray flu vaccine?

FluMist is approved for people ages 2 to 49. Studies say it is as effective as a flu shot — and, in children under 6, more effective.

Can the flu vaccine give you the flu?

The flu shot uses a killed virus, so it can't cause the flu, the CDC says.

FluMist uses a live but weakened virus, so it can on rare occasions cause "a very mild case of the flu, which is why it works better," said Dr. Tom Murwin, a pediatrician with Dean Health System.

How serious is the flu?

About 36,000 Americans die and 200,000 are hospitalized each year from the flu, most of them elderly. Last year, 86 children were reported to have died.

How is the flu different from a cold?

The flu usually comes on more suddenly, the CDC says. It can include a fever, cough, sore throat, fatigue, body aches, runny or stuffy nose — and sometimes diarrhea and vomiting (more commonly in children than adults).

When should I get a shot?

Soon. It takes about two weeks for the shots to take effect, and flu activity in Wisconsin can begin as early as November, said Christi Archer, community health and wellness manager at Home Health United, which organizes many of the flu shot clinics in the Madison area.

How bad will this flu season be?

Nobody knows. Last year was moderate to severe, said Tom Haupt, influenza coordinator for the Wisconsin Department of Health Services. Activity peaked in early March. The two previous flu seasons were relatively light.

How effective is the vaccine?

It usually protects against the flu 70 percent to 90 percent of the time, the CDC says.

Wasn't the vaccine a bad match last year?

Yes. Two of its three strains didn't match the types of flu that circulated most widely, but the vaccine still offered some protection, the CDC says. This year's vaccine contains different strains, but it's too early to tell what strains will circulate most this year.

Will there be enough vaccine this year?

Yes. The CDC expects at least 143 million doses of flu vaccine to be available, more than the country has produced before.

Is there anything I can do?

Yes. If you see a health care provider within 48 hours after symptoms arise, you can get antiviral drugs that can lessen the length and severity of the disease.