Influenza — what most of us call "the flu" — is a highly contagious viral infection of the respiratory tract.
Flu season runs from October to May. It's best to get a flu vaccine as early in the season as possible, as it gives the body a chance to build up immunity to (protection from) the flu. But getting a flu vaccine later in the season is still better than not getting the vaccine at all.
The Centers for Disease Control and Prevention (CDC) now recommends a flu vaccine for everyone 6 months of age and older (instead of just certain groups, as was recommended before).
But it's especially important that those in higher-risk groups get vaccinated to avoid health problems as a result of the flu. They include:
- all kids 6 months through 4 years old
- anyone 65 years and older
- all women who are pregnant, are considering pregnancy, have recently given birth, or are breastfeeding during flu season
- anyone whose 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
- caregivers or household contacts of anyone in a high-risk group (like children younger than 5 years old, especially those younger than 6 months, and those with high-risk conditions)
- Native Americans and Alaskan natives
Babies younger than 6 months can't get the vaccine, but if their parents, other caregivers, and older kids in the household get it, that will help protect the baby. This is important because infants are more at risk for serious complications from the flu.
- Kids younger than 9 years old who are getting the flu vaccine for the first time will receive two separate doses 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 vaccines they've received since then is unknown. This is to ensure that all kids are vaccinated against the H1N1 flu strain that surfaced in 2009.
- Kids older than 9 years old need only one dose of the vaccine.
Talk to your doctor about how many doses your child needs.
Types of Vaccines
Different types of vaccines are available. One type (called trivalent) protects against three strains of the flu virus (usually, two types of influenza A viruses and one influenza B virus). Another (called quadrivalent) protects against four strains.
The vaccine can be given to kids in two different ways: by injection with a needle (the flu shot), or sprayed into the nostrils (nasal spray or nasal mist).
Both ways of delivering the vaccine are effective, but recent studies show that the nasal spray may work better in younger children. So experts recommend that healthy kids 2 to 8 years old get the nasal spray vaccine when available. If it's not available, the flu shot should be given (kids should not wait for the nasal spray to get vaccinated). The nasal spray isn't recommended for kids with certain medical conditions or pregnant women.
Some vaccines are approved only for adults at this time, such as egg-free vaccines and intradermal shots, which are injected into the skin (instead of muscle) with a smaller needle.
Vaccine shortages and delays sometimes happen, so check with your doctor about availability and to see which vaccine is right for your kids.
Why the Vaccine Is Recommended
While the flu vaccine isn't 100% effective, it still greatly reduces a person's chances of catching the flu, which can be very serious. It also can make symptoms less severe if someone does still get the flu after immunization.
Even if you or your kids got the flu vaccine last year, that won't protect you this year, because flu viruses constantly change. That's why the vaccine is updated each year to include the most current strains of the virus.
Sometimes the same strains are included in the vaccine one year after the next. In this case, it's still important to get a seasonal flu shot because the body's immunity against the influenza virus declines over time.
Usually given as an injection in the upper arm, the flu shot contains killed flu viruses that will not cause someone to get the flu, but can cause mild side effects like soreness, redness, or swelling at the injection site. A low-grade fever and aches are also possible.
The nasal spray flu vaccine contains weakened live flu viruses, so it may cause mild flu-like symptoms, including runny nose, headache, vomiting, muscle aches, and fever. Very rarely, the flu vaccine can cause a severe allergic reaction.
When to Delay or Avoid Immunization
Certain things might prevent a person from getting the vaccine. Talk to your doctor to see if the vaccine is still recommended if your child:
- has ever had a severe reaction to a flu vaccination
- has 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.
Still, a child with an egg allergy 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.
Caring for Your Child After Immunization
Check with your doctor to see if you can give either acetaminophen or ibuprofen for pain and fever and to find out the appropriate dose.
A warm, damp cloth or a heating pad at the injection site also may help ease soreness. Moving or using the limb that has received the injection often reduces the soreness as well.
When to Call the Doctor
- Call if you aren't sure if the vaccine should be postponed or avoided.
- Call if there are serious problems after the immunization, such as an allergic reaction or high fever, or if you have other concerns.
Reviewed by: Elana Pearl Ben-Joseph, MD
Date reviewed: February 2015