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FluMist Side Effects

Generic name: influenza virus vaccine, live

Medically reviewed by Last updated on Oct 1, 2023.

Note: This document contains side effect information about influenza virus vaccine, live. Some dosage forms listed on this page may not apply to the brand name FluMist.

Applies to influenza virus vaccine, live: nasal spray.

In 1976, a number of people who received the “swine fluinfluenza vaccine developed Guillain-Barré syndrome (GBS), which is a disease that may cause paralysis. Most of these people were over 25 years of age. Although only 10 out of every one million people who received the vaccine actually developed GBS, this number was 6 times higher than would normally have been expected. Most of the people who got GBS recovered completely.

It is assumed that the “swine flu” virus included in the 1976 vaccine caused the problem, but this has not been proven. Since that time, the “swine flu” virus has not been used in influenza vaccines, and there has been no recurrence of GBS that was associated with influenza vaccinations.

Serious side effects of FluMist

Along with its needed effects, influenza virus vaccine, live (the active ingredient contained in FluMist) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking influenza virus vaccine, live:

More common

Less common


Incidence not known

Other side effects of FluMist

Some side effects of influenza virus vaccine, live may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

Incidence not known

For Healthcare Professionals

Applies to influenza virus vaccine, live: nasal spray.


The most common adverse events were nasal congestion, headache, sore throat, and tiredness.[Ref]


Very common (10% or more): Runny nose/nasal congestion (58%), sore throat (28%), cough (14%)

Common (1% to 10%): Wheezing, sinusitis, sneezing

Uncommon (0.1% to 1%): Epistaxis[Ref]

In a clinical trial, among children 6 to 23 months of age, wheezing requiring bronchodilator therapy or with significant respiratory symptoms occurred in 5.9% of FluMist recipients compared to 3.8% of active control (injectable influenza vaccine made by Sanofi Pasteur Inc) recipients (Relative Risk 1.5, 95% CI: 1.2, 2.1). Wheezing was not increased in children 24 months of age and older.[Ref]

Nervous system

Very common (10% or more): Headache (44%), decreased activity/lethargy (18%)

Postmarketing reports: Exacerbation of symptoms of mitochondrial encephalomyopathy (Leigh syndrome), Guillain-Barre syndrome, Bell's Palsy, meningitis, eosinophilic meningitis, vaccine-associated meningitis[Ref]


Very common (10% or more): Tiredness/weakness (26%), fever (16%)

Common (1% to 10%): Hospitalizations, otitis media[Ref]


Very common (10% or more): Muscle aches (17%), abdominal pain (12%)

Common (1% to 10%): Chills[Ref]


Very common (10% or more): Decreased appetite (21%)[Ref]


Uncommon (0.1% to 1%): Hypersensitivity reactions (including anaphylactic reaction, facial edema, and urticaria)[Ref]


Postmarketing reports: Nausea, vomiting, diarrhea[Ref]


Postmarketing reports: Rash[Ref]


Postmarketing reports: Pericarditis[Ref]

Frequently asked questions


1. Product Information. FluMist (influenza virus vaccine, live). Medimmune Inc. 2022.

2. Cerner Multum, Inc. UK Summary of Product Characteristics.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.