Flu (Influenza) Vaccine Side Effects
Flu shots do not usually cause severe side effects, but patients should seek medical attention for any unusual conditions. The severe side effects include high fever, behavior changes, allergic reaction, and Guillain-Barré Syndrome.
What are flu vaccine names?
The following is a list of influenza (flu) vaccine names and links to information on side effects:
Can the flu vaccine cause the flu?
No. Some people who get a flu shot develop mild flu-like symptoms as their body develops immunity, but flu shots can’t actually cause the flu. The vaccines are either inactivated or recombinant, which means the viruses in the vaccines are not infectious or they are particles disguised as a flu virus to trick the immune system.
What are common side effects?
- Bruising
- Chills
- Cough
- Diarrhea
- Ear ache
- Fatigue
- Fever
- Headache
- Itching
- Irritability
- Joint pain
- Lump where the shot was given
- Muscle aches
- Nausea
- Pain
- Rash
- Runny nose
- Soreness, redness, or swelling from the shot
- Tiredness
- Vomiting
What are rare side effects?
Flu vaccines cause fevers in 1-2% of people in all age groups, but younger children are more likely to develop high fevers. Sometimes, fevers cause a child to experience spasms or jerky movements called seizures. These are known as febrile seizures.
Shoulder Injury Related to Vaccine Administration (SIRVA) is a rare side effect of the flu shot. It occurs when the needle punctures the bursa, tendons, or ligaments in the shoulder. SIRVA can cause chronic shoulder pain and permanent limited mobility that causes disability.
What are severe side effects?
The risk depends on the vaccine, but the following is a list of severe side effects that have been reported after flu vaccines:
- Allergic reaction
- Anaphylaxis
- Anaphylactic shock
- Angioedema
- Arthritis
- Asthma
- Bell’s palsy
- Brachial plexus neuropathy
- Brain damage
- Cellulitis
- Coma
- Convulsions
- Cranial nerve paralysis
- Death
- Encephalopathy
- Encephalomyelitis
- Erythema multiforme
- Extensive limb swelling
- Febrile seizures
- Fever
- Flu-like illness
- Fainting
- Infection
- Guillain-Barré Syndrome
- Meningitis
- Microscopic polyangitis
- Migraine headache
- Myelitis
- Nerve damage (neuropathy)
- Neuralgia
- Neurological disorders
- Numbness and tingling
- Optic neuritis
- Paresthesia
- Paralysis
- Partial facial paralysis
- Rash
- Respiratory distress
- Seizure
- Serum sickness
- SIRVA (Shoulder Injury Related to Vaccine Administration)
- Skin reactions
- Spinal cord inflammation
- Stevens-Johnson Syndrome
- Syncope and pre-syncope (fainting)
- Tachycardia
- Thrombocytopenia
- Tonic-clonic limb movements
- Transverse myelitis
- Upper respiratory tract infection
- Vasculitis with transient kidney involvement
- Vision problems
What are symptoms of an allergic reaction?
Flu shots can cause allergic reactions in people who are hypersensitive to eggs, latex, or other ingredients in the vaccine. Life-threatening allergic reactions like anaphylaxis or angioedema are rare.
The symptoms usually appear within a few hours. Signs of a severe allergic reaction can include:
- Trouble breathing
- Hoarseness or wheezing
- Swelling around the eyes and lips
- Hives
- Paleness
- Weakness
- Fast heartbeat
- Dizziness
What is Guillain-Barré Syndrome?
Guillain-Barre Syndrome (GBS), pronounced “gee-YAH-buh-RAY” syndrome is a rare disorder in which the body’s immune system attacks the peripheral nervous system and causes nerve damage. The symptoms include:
- Extreme muscle weakness
- Paralysis
- Painful tingling or burning
- Problems walking or coordinating movements
- Fatigue
Some studies have found a possible small increased risk of GBS with injectable flu vaccines. Overall, these studies estimate the risk for GBS after vaccination with less than 1 or 2 cases per million people who are vaccinated. Other studies have found no risk.
