Common and Serious Flu Shot Reactions

Millions of people get flu shots every year and have no reactions at all. However, there are some common flu shot reactions and also those that are very rare but could be serious.

There are two different types of flu vaccines—the flu shot (intramuscular injection) and the nasal spray flu vaccine. Many of the reactions they may cause are similar, but there are some differences.

• Pain at injection side
• Redness and swelling at injection site
• Headache
• Fatigue or malaise (feeling tired)
• Red or itchy eyes
• Hoarse voice
• Cough
• Fever

• Runny nose, congestion, or cough
• Fever
• Headache or muscle aches
• Wheezing (typically in children)
• Abdominal pain or occasional vomiting or diarrhea (typically in children)
• Sore throat
• Weakness or fatigue (feeling tired)

Serious and life-threatening flu shot reactions occur very rarely. Reactions you should be aware of and know the signs for include:

• Anaphylaxis - this is a severe, life-threatening allergic reaction. A person can have an anaphylactic reaction to any component of the vaccine. If you know you are allergic to any of the ingredients in the flu vaccine (especially chicken eggs), you should not get the flu shot or the nasal spray flu vaccine. Signs of anaphylaxis include difficulty breathing, difficulty swallowing, swelling of the tongue and lips, coughing and wheezing. Some people also experience dizziness, weakness, vomiting, and rash.
• Guillain-Barre Syndrome - a swine flu vaccine that was administered in 1976 was linked to Guillain-Barre syndrome. Since then, no link has been identified between seasonal flu vaccines and this disorder. It occurs in 1 to 2 people out of every million that get the flu shot.

The flu shot provides protection against the specific strain of the flu that researchers believe will be causing illnesses that season for most people. Every year, the flu virus mutates and changes; therefore, new vaccines have to be made and administered each season.

There are certain people who should get flu shots. For example, anyone over the age of 65 is considered to be in a high-risk category and should have a flu vaccine every year. The vaccine is not quite as effective at preventing the flu in this age group. However, among older adults who do not have chronic illnesses and who do not live in nursing homes, the shot is 30% to 70% effective at preventing hospitalizations from pneumonia and the flu.

The other group of people at highest risk for serious complications from the flu is children, especially those under 5 years old. Children under 6 months old are at highest risk for complications from the flu, but they are too young to receive the vaccine. For this reason, it is very important for parents and caregivers of infants to get the flu vaccine. The vaccine can prevent up to 66% of flu infections in young children, with the numbers being even higher for older children.