Influenza Virus Vaccine, H1n1, Inactivated Side Effects

Medically reviewed by Drugs.com. Last updated on Jun 25, 2024.

Applies to influenza virus vaccine, h1n1, inactivated: intramuscular suspension.

Important warnings This medicine can cause some serious health issues

The injectable H1N1 influenza virus vaccine is a "killed virus" vaccine. H1N1 influenza virus vaccine is also available in a nasal spray form, which is a "live virus" vaccine. This medication guide addresses only the injectable form of this vaccine.

H1N1 influenza is sometimes called "swine flu" because it is usually found in pigs. You cannot become infected with H1N1 influenza from eating pork products.

The injectable form of H1N1 influenza virus vaccine is a "killed virus" vaccine and will not cause you to become ill with the flu virus that it contains. However, you may have flu-like symptoms at any time during flu season that may be caused by other strains of influenza virus.

Do not receive this vaccine if you have ever had an allergic reaction to a flu vaccine, or if you are allergic to eggs.

Before you receive an H1N1 influenza virus vaccine, tell your doctor if you have a weak immune system, or a history of Guillain-Barré syndrome or neurologic disorder affecting the brain (especially if these were caused by a vaccine).

You can still receive an H1N1 influenza vaccine if you have a cold or fever. In the case of a more severe illness with a fever or any type of infection, wait until you get better before receiving this vaccine.

Keep track of any and all side effects you have after receiving this vaccine. If you ever have to receive another influenza virus vaccine in the future, you will need to tell the doctor if the first shot caused any side effects.

Like any vaccine, H1N1 influenza virus vaccine may not provide protection from disease in every person. This vaccine will not prevent illness caused by avian flu ("bird flu").

Becoming infected with influenza is much more dangerous to your health than receiving the vaccine to protect against it. Most people with H1N1 influenza have recovered, but the virus has caused some deaths.

The injectable form of H1N1 influenza virus vaccine is a "killed virus" vaccine and will not cause you to become ill with the flu virus that it contains. However, you may have flu-like symptoms at any time during flu season that may be caused by other strains of influenza virus.

You should not receive a booster vaccine if you had a life-threatening allergic reaction after the first shot.

Keep track of any and all side effects you have after receiving this vaccine. If you ever have to receive another H1N1 influenza virus vaccine in the future, you will need to tell the doctor if the first shot caused any side effects.

Get emergency medical help if you have any of these signs of an allergic reaction while taking influenza virus vaccine, h1n1, inactivated: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any of these serious side effects:

• weakness, numbness or tingly feeling in your feet and spreading upward;

• problems with vision, speech, swallowing, or bladder and bowel functions;

• severe lower back pain;

• slow heart rate, trouble breathing, feeling like you might pass out;

• high fever; or

• unusual bruising or bleeding.

Less serious side effects can last a day or two after you receive this vaccine and may include:

• runny or stuffy nose;

• low fever;

• sore throat;

• loss of appetite;

• headache, tired feeling; or

• muscle pain.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For healthcare professionals

Applies to influenza virus vaccine, h1n1, inactivated: intramuscular suspension.

General adverse events

The most common adverse events were soreness at the injection site lasting less than 2 days, and local pain and swelling.^[Ref]

Local

• Very common (10% or more): Soreness at vaccination site lasting under 2 days (64%)
• Frequency not reported: Local pain and swelling^[Ref]

Nervous system

• Frequency not reported: Headache, Guillain-Barre Syndrome, convulsions, myelitis (including encephalomyelitis and transverse myelitis), facial palsy (Bell's palsy), optic neuritis/neuropathy, brachial neuritis, syncope (shortly after vaccination), dizziness, paresthesia^[Ref]

Hypersensitivity

• Postmarketing reports: Anaphylaxis, other allergic/hypersensitivity reactions (including urticaria, angioedema)^[Ref]

Dermatologic

• Postmarketing reports: Stevens-Johnson syndrome, pruritus^[Ref]

Respiratory

• Postmarketing reports: Dyspnea, pharyngitis, rhinitis^[Ref]

Musculoskeletal

• Frequency not reported: Myalgia^[Ref]

Hematologic

• Postmarketing reports: Thrombocytopenia, lymphadenopathy^[Ref]

Other

• Frequency not reported: Fever, malaise
• Postmarketing reports: Pain, asthenia/fatigue, pain in extremities, chest pain^[Ref]

Cardiovascular

• Postmarketing reports: Vasculitis, vasodilation/flushing^[Ref]

Further information

Influenza virus vaccine, h1n1, inactivated side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer