influenza A (H5N1) vaccine

Influenza A (H5N1) vaccine is an inactivated viral vaccine used to immunize against H5N1 influenza, also known as avian flu. Influenza A (H5N1) vaccine is administered as an intramuscular injection to individuals older than 6 months who are at an increased risk of exposure to the influenza A (H5N1) virus.

Avian flu is not very common in humans and is contracted from exposure to infected wild birds or poultry. People who work at bird rehabilitation centers, bird and other animal sanctuaries, responders to bird flu outbreaks and poultry farmers are at an increased risk for exposure to avian flu virus. Influenza A (H5N1) vaccine availability in the U.S. is limited to CDC distribution from Strategic National Stockpile in consultation with local health department.

Influenza A (H5N1) vaccine stimulates the body’s immune system to produce antibodies against the influenza A (H5N1) virus, and protects the vaccinated individual from developing serious illness when exposed to the virus. The vaccine is prepared from virus grown in mammalian cells, which is then purified and inactivated to eliminate its disease-causing capability.

Influenza A (H5N1) vaccine contains sterile viral surface proteins (antigens) known as hemagglutinins that help the virus adhere to the human respiratory cells and enter inside to replicate. The vaccinated person’s immune system has antibodies that identify the virus by its specific antigen and prevent it from entering the cell to multiply and infect other cells.

• Do not administer the influenza A (H5N1) vaccine to anyone with a history of severe allergic reactions (anaphylaxis) to any component of the vaccine, or to anyone who has had a severe reaction to a previous dose of flu vaccine.
• Medical facilities for appropriate management of anaphylactic reactions following the vaccination should be available at the vaccination facility.
• Vaccination administered too high on the arm can cause shoulder injury and pain. Exercise care to administer the injection using proper technique.
• Intramuscular injections may cause hematoma or bleeding in people with bleeding disorders, administer with caution.
• Do not delay vaccination for minor illnesses, but defer the vaccine in febrile illnesses until the illness is resolved.
• Influenza A (H5N1) vaccine may be associated with an elevated risk for Guillain-Barre syndrome (GBS), although the evidence is inconclusive. If a person has experienced GBS within 6 weeks after a previous flu vaccine, weigh potential benefits and risks before administering the vaccine.
• Fainting (syncope) has been reported in some individuals, following vaccination. Follow precautions to prevent falling and injury.
• Immunocompromised individuals, including those on immunosuppressive treatment may have diminished response to the vaccine.
• Influenza A (H5N1) vaccine may not protect all vaccine recipients against disease.

Common side effects of influenza A (H5N1) vaccine include:

• Injection site reactions including:
  • Pain
  • Tenderness
  • Redness (erythema)
  • Hardening of tissue (induration)
  • Swelling 

Common systemic side effects of influenza A (H5N1) vaccine include:

Infants and children (6 months through 5 years of age):

• Irritability
• Fussiness
• Sleepiness
• Change in eating habits
• Fever

Children and adolescents (6 years through 17 years of age):

• Muscle pain (myalgia)
• Fatigue
• Feeling unwell (malaise)
• Headache
• Loss of appetite
• Nausea
• Vomiting
• Diarrhea
• Abdominal pain
• Joint pain (arthralgia)
• Sweating
• Shivering
• Fever

Adults of age 18 to 64 years:

• Fatigue
• Headache
• Malaise
• Myalgia
• Arthralgia
• Nausea
• Shivering
• Sweating
• Fever

Adults 65 years of age or above:

• Injection site pain
• Fatigue
• Malaise
• Headache
• Arthralgia

Less common side effects of influenza A (H5N1) vaccine include:

• Injection site reactions including:
  • Inflammation
  • Mass
  • Ulcer
  • Tissue death (necrosis)
• Lymph node swelling (lymphadenopathy)
• Hypersensitivity reactions including:
  • Swelling beneath the skin and in the mucous tissue (angioedema)
  • Severe allergic reactions (anaphylaxis)
• Skin reactions including:
  • Hives (urticaria)
  • Itching (pruritus)
  • Generalized rash
• Bell’s palsy
• Convulsions, including fever-induced convulsions
• Nerve inflammation (neuritis)
• Brain inflammation (encephalitis)
• Damage to myelin, the substance that protects nerve fibers (demyelination)
• Guillain-Barre syndrome, a condition in which the immune system attacks the nerves
• Tingling and numbness (paresthesia)
• Fainting (syncope)
• Muscular weakness
• Drowsiness
• Sleep disorder (narcolepsy)

Call your doctor immediately if you experience any of the following symptoms or serious side effects while using this drug:

• Serious heart symptoms include fast or pounding heartbeats, fluttering in your chest, shortness of breath, and sudden dizziness;
• Severe headache, confusion, slurred speech, severe weakness, vomiting, loss of coordination, feeling unsteady;
• Severe nervous system reaction with very stiff muscles, high fever, sweating, confusion, fast or uneven heartbeats, tremors, and feeling like you might pass out; or
• Serious eye symptoms include blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights.

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.

Supplied only to government agencies and for stockpiles

Injection, emulsion AS03 adjuvant (Adult)

• 3.75 mcg/mL hemagglutinin (HA) of the H5N1 influenza virus strain 364 A/Indonesia/05/2005

Injection, emulsion AS03 adjuvant (Pediatric)

• 3.75 mcg/0.5 mL hemagglutinin (HA) of the H5N1 influenza virus strain 364 A/Indonesia/05/2005

Injection, emulsion MF59 adjuvant (Audenz)

• 7.5 mcg/0.5 mL HA of the H5N1 influenza virus strain A/turkey/Turkey/1/2005

H5N1 Influenza (Avian Flu) Immunization

Adult:

• Indicated for active immunization to prevent disease caused by the influenza A virus H5N1 subtype in adult patients at increased risk of exposure
• 2-dose series: 0.5 mL intramuscular (IM) administered 21 days apart

Pediatric:

• Indicated for active immunization to prevent disease caused by the influenza A virus H5N1 subtype in patients aged above 6 months at increased risk of exposure

Children below 6 months:

• Safety and efficacy not established

Children 6 months through 17 years:

AS03 adjuvant

• 2-dose series: 0.25 mL IM administered 21 days apart

MF59 adjuvant (Audenz)

• 2-dose series: 0.5 mL IM administered 21 days apart

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

• Severe interactions of influenza A (H5N1) vaccine include:
  • belimumab
• Serious interactions of influenza A (H5N1) vaccine include:
  • elivaldogene autotemcel
  • ocrelizumab
  • ofatumumab SC
  • secukinumab
  • siponimod
  • teplizumab
• Influenza A (H5N1) vaccine has moderate interactions with at least 58 different drugs.
• Mild interactions of influenza A (H5N1) vaccine include:
  • ozanimod

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider of all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or health care provider if you have any questions about the medication.

• There is insufficient information on influenza virus vaccine use in pregnant women to determine vaccine-related fetal malformations or adverse effects. Animal reproductive studies showed no evidence of fetal harm with influenza A (H5N1) vaccination.
• There is limited information on the risk of influenza A (H5N1) infection in pregnant women. Pregnant women infected with pandemic H1N1 or seasonal influenza are at a higher risk than non-pregnant women for serious illness and complications from influenza. Pregnant women who contract influenza may be at an increased risk for preterm labor and delivery.
• There is no data on the presence of influenza A (H5N1) vaccine in breastmilk, or on its effect on milk production or on the breastfed infant. Decision to breastfeed should be made after considering the developmental and health benefits of breastfeeding, along with the potential adverse effects to the infant from the vaccine or the mother’s susceptibility to contracting avian influenza

• Complete your two-dose immunization series of influenza A (H5N1) vaccine if you are at an increased risk for avian flu. Getting vaccinated is the best way to prevent disease, in addition to following safe practices to avoid exposure to the avian flu virus.
• Influenza A (H5N1) vaccine contains only noninfectious surface proteins of the virus and cannot cause influenza.