Flu vaccine side effects range from the tolerable to the uncomfortable. Only on rare occasion do they venture into the life-threatening category.

In general, there are two types of flu vaccines.

The first one, inactivated (killed) vaccine, is the typical flu shot many people receive each year.

The second one, the live, weakened influenza vaccine is a spray that patients breathe in through the nostrils.

There also is a “high dose” inactivated vaccine for people over the age of 65.

The U.S. Centers for Disease Control and Prevention (CDC) recommends that all people ages 6 months and older receive a flu vaccine annually because the virus changes from year to year.  The inactive (killed) vaccine can fit the bill for most people.

The live virus version, however, is not recommended for everyone.

In fact, the CDC says the live version should only be used for healthy people aged 2 to 49 who are not pregnant and do not have a weakened immune system or long-term health problems such as heart disease, lung disease, asthma, kidney disease, diabetes or blood disorders. 

Side effects

According to the CDC, some children and adolescents aged 2 to 17 have reported the following side effects after receiving the live version of the flu vaccine:

  • Runny nose
  • Nasal congestion
  • Cough
  • Headache and muscle aches
  • Abdominal pain
  • Occasional vomiting
  • Diarrhea
  • Fever
  • Wheezing
In addition, some adults aged 18 to 49 have reported the following side effects after receiving the live version of the vaccine:
  • Runny nose
  • Nasal congestion
  • Cough
  • Chills
  • Tiredness/weakness
  • Sore throat
  • Headache
In extremely rare situations, some patients experience a life-threatening allergic reaction after receiving a flu vaccine. The CDC says these types of reactions occur within a few minutes to a few hours after the vaccination.

It takes about two weeks to build up protection against the flu once a patient has been vaccinated. The CDC says the protection lasts one year.

Related on MNN: