Children's Vaccines Health Center

Seasonal Flu Shot and Nasal Spray

How Effective Is the Seasonal Flu Vaccine?

The seasonal flu vaccine is about 80% effective in preventing flu. It takes about two weeks for the body to become protected after getting the seasonal flu vaccine.

The viruses used in the vaccine may not be the only strains causing the flu. So it's possible you could be infected with a virus you do not have immunity against. People who get the flu after getting a flu shot typically have a milder and shorter case of flu.

Who Should Get a Seasonal Flu Vaccine?

The seasonal flu vaccine is recommended for all children older than 6 months as well as teenagers.

It's also recommended for adults considered to be at higher risk of complications. That includes:

• People with chronic diseases such as diabetes mellitus, kidney disease, heart disease, lung disease, and a weakened immune system, such as from HIV/AIDS or as a result of therapy.
• Pregnant women
• Residents of nursing homes and other facilities where people have chronic medical conditions
• Health care workers
• People planning to travel to the tropics at any time and people who were not vaccinated but are going to the Southern Hemisphere from April through September
• People 50 years of age or older
• Caregivers and household contacts of anyone in a high-risk group

The vaccine is also recommended for anyone else who wants to be protected against this year's flu.

If a child is between 6 months and 8 years and is being vaccinated against flu for the first time (or was vaccinated for the first time during the previous flu season but only got one dose) he or she should get two doses, separated by at least four weeks.

Are There Some People Who Should Not Get a Flu Vaccine?

The ingredients for flu shots are grown inside eggs. So anyone with a severe allergy to eggs or egg products should not get a flu shot. Other people who should not get a flu shot include:

• Infants under 6 months old.
• Anyone who has had a severe reaction to a past flu shot or nasal spray.
• Someone with Guillain-Barre syndrome.
• People with moderate to severe illness with a fever; they should be vaccinated after they have recovered. 

It's long been advised that people with allergies to eggs should not get the flu shot. However, the American College of Allergy, Asthma and Immunology says the vaccine contains such a low amount of egg protein that it's unlikely to cause an allergic reaction in those with an egg allergy. If you have a severe egg allergy (anaphylaxis), talk to your doctor before getting the flu vaccine. Also, a flu vaccine that is not made with the use of eggs is available. The vaccine, called Flublok, is approved for use in those 18 to 49 years old.