Although the flu season lasts from October until May, with most cases occurring between late December and early March, the flu vaccine is usually offered between September and mid-November. Getting the shot before the flu season is in full force gives the body a chance to build up immunity to, or protection from, the virus.

Even though it's ideal to get vaccinated early, the flu shot can still be helpful later. Even as late as January, there are still a few months left in the flu season, so it's still a good idea to get protected.

Who Should Get the Flu Shot?

Although flu vaccine is recommended for everyone aged 6 months or older, in times when the vaccine is in short supply, certain people need it more than others. The Centers for Disease Control and Prevention (CDC) often will recommend that certain high-risk groups be given priority when flu shot supplies are limited. Call your doctor or local public health department about vaccine availability in your area.

The American Academy of Family Physicians (AAFP), the American Academy of Pediatrics (AAP), and the CDC recommend that certain high-risk groups be given priority for receiving the flu shot in times of shortage:

• all kids 6 months through 4 years old
• anyone 65 years and older
• women who will be pregnant during flu season
• anyone whose weakened immune system is weakened from medications or illnesses (like HIV infection)
• residents of long-term care facilities, such as nursing homes
• any adult or child with chronic medical conditions, such as asthma
• kids or teens who take aspirin regularly and are at risk for developing Reye syndrome if they get the flu
• health care personnel who have direct contact with patients
• caregivers or household contacts of anyone in a high-risk group (like children younger than 6 months)
• Native Americans and Alaskan Natives

Ideally, kids and adults should be immunized in October so they're adequately protected before flu season hits.

Kids under 9 years old who are getting the flu shot for the first time will receive two separate shots at least a month apart. Those under 9 who have received the flu vaccine before still might need two doses if they did not receive at least two vaccines since July 2010, or if the number of shots they've received since July 2010 is unknown. This is to ensure that all children are vaccinated against the H1N1 flu strain that surfaced in 2009. Kids older than 9 years old only need one dose of the vaccine.

It can take 1 to 2 weeks for the flu shot to become effective, so it's best to get vaccinated as soon as possible if your doctor thinks it's necessary.

Those Who Should Not Get a Flu Shot

Certain circumstances would prevent a person from getting the flu shot. If your child falls into any of the groups below, talk to your doctor to see if a flu shot is recommended:

• infants under 6 months old
• anyone who's ever had a severe reaction to a flu vaccination
• anyone with Guillain-Barré syndrome (a rare condition that affects the immune system and nerves)

In the past, it was recommended that anyone with an egg allergy talk to a doctor about whether receiving the flu vaccine was safe because it is grown inside eggs. But health experts now say that the amount of egg allergen in the vaccine is so tiny that it (but not the nasal mist) is safe even for kids with a severe egg allergy. This is especially important during a severe flu season, such as the current one, which started earlier and has been much worse than in years past.

Still, if your child has an egg allergy, he or she should get the flu shot in a doctor's office, not at a supermarket, drugstore, or other venue. And if the allergy is severe, it might need to be given in an allergist's office.

If your child is sick and has a fever, talk to your doctor about rescheduling the flu shot.

A non-shot option, the nasal mist vaccine, is now available, but because it contains weakened live flu viruses it is not for people with weakened immune systems or certain health conditions. The nasal mist vaccine is only for healthy, non-pregnant people between the ages of 2 and 49 years. Check with your doctor to see if your child can — or should — get this type of flu vaccine.

Are There Side Effects?

Most people do not experience any side effects from the flu shot. Some have soreness or swelling at the site of the shot or mild side effects, such as headache or low-grade fever.

Some people who get the nasal spray vaccine also may develop mild flu-like symptoms, including runny nose, headache, vomiting, muscle aches, and fever.

Where Can My Family Get Flu Shots?

Flu shots are available at:

• many health care settings, including doctors' offices and public, employee, and university health clinics
• some pharmacies
• some supermarkets
• some community groups or centers
• some schools

If you have an HMO insurance plan, be sure to check with your primary care doctor before having your kids vaccinated outside the office, since most HMOs will pay for shots only if they're given through their plan.

Flu shots are covered by Medicare for senior citizens and are generally covered by insurance for people in other high-risk groups. Otherwise, flu shots may cost anywhere from $10 to $50. If you opt for the nasal mist flu vaccine, check to see if your insurance plan covers it.

Reviewed by: Elana Pearl Ben-Joseph, MD
Date reviewed: January 2013