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 will receive two doses of flu vaccine this flu season if they have received fewer than two doses before July 2015. This includes kids who are getting the flu vaccine for the first time.
Those under 9 who have received at least two doses of flu vaccine previously (in the same or different seasons) will only need one dose.
Kids older than 9 need only one dose of the vaccine.
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 is currently recommended to be given to kids by injection with a needle (the flu shot). It is safe and effective.
The nasal spray or nasal mist, which was sprayed into the nostrils, is not currently recommended for kids because the Centers for Disease Control (CDC) found that the nasal version did not prevent cases of the flu between 2013 and 2016. Researchers aren't sure why the nasal flu vaccine stopped working, but the doctors, nurses, and scientists who make up the CDC's Advisory Committee on Immunization Practices (ACIP) decided it's not a good idea to keep giving the nasal version of the vaccine at this time.
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.
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.
Possible Side Effects
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.
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 flu 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 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
you aren't sure if the vaccine should be postponed or avoided
there are problems after the immunization, such as an allergic reaction or high fever, or if you have other concerns