influenza virus vaccine

The influenza virus vaccine is a sterile biologic product that provides immunity against seasonal influenza. Influenza virus vaccine works by stimulating the body’s immune system to produce antibodies against influenza virus, and protects a person from developing infection when exposed to the virus. The current influenza vaccine is a quadrivalent vaccine that protects against infection from four strains of influenza virus.

• Influenza virus vaccines are inactivated viral vaccines that contain particles of proteins or genetic material from influenza virus. Most influenza virus vaccines are prepared from viruses grown in embryonated chicken eggs, however, there are also egg-free vaccines produced in insect or mammalian cells. The viruses are then inactivated and purified to eliminate their disease-causing capability. Inactivated viral vaccines may also contain substances that preserve and stabilize the vaccine, and enhance immune response.
• The primary active components of influenza virus vaccines are the surface proteins (antigens) known as hemagglutinins that help the virus adhere to a human cell, enter inside and replicate, and DNA/RNA fragments from the virus. The immune system of the vaccinated individual produces antibodies to the influenza virus and if exposed to it later, the immune system recognizes the viral antigen and fights infection by preventing the virus from attaching and entering the host cell.
• There are several types of influenza vaccines approved by the FDA, some of which are standard flu vaccines for all individuals older than 6 months, some are meant only for adults, and some are intended for individuals older than 65 years of age. A person’s suitability for vaccination and the type of flu vaccine may be determined by various factors including their age, health, and allergies to any of the vaccine components.
• Flu vaccines are mostly administered as intramuscular (IM) injections, but an additional option available is an egg-based, live, attenuated flu nasal spray vaccine with the brand name FluMist Quadrivalent, made with weakened live influenza viruses, approved for use in individuals of age 2 years to 49 years. This vaccine is not recommended for use in pregnant people, immunocompromised people, or people with certain medical conditions.

• Do not administer the influenza virus vaccine to anyone with a history of severe allergic reactions (anaphylaxis) to any component of the vaccine, including egg protein, or to anyone who has had a severe reaction to previous flu vaccination.
• Medical facilities for appropriate management of anaphylactic reactions following the vaccination should be available at the vaccination facility.
• Influenza virus 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 flu vaccine.
• Vaccine administration to individuals with minor illnesses without fever may be acceptable, but defer the vaccine in febrile illnesses until the illness is resolved.
• Immune response to the vaccine may be lower in individuals who are immunocompromised, including those on immunosuppressant or corticosteroid treatments.
• The influenza virus vaccine may not protect all vaccine recipients against disease.
• Fainting has been reported in some individuals, following vaccination. Follow precautions to prevent falling and injury.
• The tip of the syringe may contain natural rubber latex, to which some individuals may be sensitive. Exercise caution.
• Intramuscular injections may cause hematoma in people with bleeding disorders, use them with caution.
• Do not mix any other vaccine with the influenza virus vaccine. If other vaccines must be administered concurrently, administer them separately at different sites.

Common side effects of influenza virus vaccine include:

• Local reactions at the injection site including:
  • Pain
  • Tenderness
  • Swelling
  • Redness (erythema)
  • Hardening of tissue (induration)
  • Bruising
  • Blood clot under the skin (hematoma)
  • Itching

Flu shot side effects in adults

• Systemic reactions common in adults:
  • Headache
  • Fatigue
  • Feeling ill (malaise)
  • Muscle pain (myalgia)
  • Joint pain (arthralgia)
  • Diarrhea
  • Nausea
  • Vomiting
  • Loss of appetite (anorexia)
  • Chills
  • Shivering
  • Fever
  • Mouth and throat (oropharyngeal) pain

Flu shot side effects in children and adolescents

• Systemic reactions common in infants, children, and adolescents:
  • Irritability
  • Uncontrollable crying
  • Drowsiness
  • Vomiting
  • Anorexia
  • Changes in appetite
  • Fever
  • Cough
  • Nasal discharge (rhinorrhea)
  • Nasal congestion
  • Nose and throat inflammation (nasopharyngitis)
  • Flu-like symptoms
  • Skin rash

Less common symptoms of influenza virus vaccine include:

• Local reactions at the injection site including:
  • Inflammation
  • Warm sensation
  • Abscess
  • Cellulitis
• Abdominal pain and distress
• Swallowing difficulty (dysphagia)
• Swollen tongue
• Gastroenteritis
• Swelling of the injected limb, lasting longer than a week
• Facial swelling (edema)
• Flushing
• Feeling faint (presyncope)
• Fainting (syncope)
• Blood vessel dilation (vasodilation)
• Blood vessel inflammation (vasculitis)
• Henoch-Schonlein purpura, a condition that makes small blood vessels in skin, joints, kidneys and gastrointestinal tract get inflamed and bleed
• Chest pain
• Rapid heart rate (tachycardia)
• Hot flash
• Nasal inflammation (rhinitis)
• Throat inflammation (pharyngitis)
• Tonsillitis
• Throat swelling (pharyngeal edema)
• Bronchospasm
• Wheezing
• Shortness of breath (dyspnea)
• Limb pain
• Musculoskeletal pain
• Body pain
• Weakness (asthenia)
• Abnormally low motor activity (hypokinesia)
• Muscle weakness (myasthenia)
• Bell’s palsy
• Cranial nerve palsy
• Impaired mobility of the injected arm
• Inflammation of the spinal cord (myelitis)
• Inflammation of a section of the spinal cord (transverse myelitis)
• Inflammation of the brain and spinal cord (encephalomyelitis)
• Brain disease (encephalopathy)
• Tremor
• Vertigo
• Dizziness
• Feeling hot
• Insomnia
• Seizure
• Febrile seizure
• Nerve pain (neuralgia)
• Nerve inflammation (neuritis)
• Nerve disease (neuropathy)
• Guillain-Barre syndrome, a condition in which the immune system attacks the nerves
• Reduced skin sensation (hypoesthesia)
• Tingling and numbness (paresthesia)
• Paralysis
• Voice disorder
• Eye pain
• Swelling of eye
• Light sensitivity
• Eyelid edema
• Red eye (ocular hyperemia)
• Optic neuritis
• Optic neuropathy
• Hypersensitivity reactions, including:
  • Swelling under the skin and in the mucous tissue (angioedema)
  • Serum sickness
  • Type 1 hypersensitivity reaction
  • Oculorespiratory syndrome, an acute, self-limited reaction with ocular and respiratory symptoms
  • Severe allergic reaction (anaphylaxis)
  • Anaphylactic shock
  • Nonimmune anaphylaxis
• Skin reactions that include:
  • Rash at the injection site
  • Redness (erythema)
  • Hives (urticaria)
  • Bruising (ecchymosis)
  • Pallor
  • Itching (pruritus)
  • Erythema multiforme
  • Stevens-Johnson syndrome
• Excessive sweating (diaphoresis)
• Low platelet count (thrombocytopenia)
• Swelling of lymph nodes (lymphadenopathy)

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.

Intramuscular (IM) suspension

• 0.25 mL/prefilled syringe (Fluzone Quadrivalent)
• 0.5 mL/prefilled syringe (Afluria Quadrivalent, Fluzone Quadrivalent, FluLaval Quadrivalent, Fluarix Quadrivalent)
• 0.5 mL/vial (Fluzone Quadrivalent)
• 5 mL/vial (Afluria Quadrivalent, Fluzone Quadrivalent, FluLaval Quadrivalent)

IM suspension injection, high-dose

• 240 mcg/0.7mL (Fluzone High-dose Quadrivalent)

IM solution

• 0.5 mL/prefilled syringe (Flublok Quadrivalent)

Emulsion for IM injection

• 0.5 mL/prefilled syringe (Fluad Quadrivalent)

Influenza Prophylaxis

• CDC’s ACIP recommends that everyone aged 6 months and older receive an annual influenza vaccination
• For more vaccine information see http://www.cdc.gov/vaccines/

Adult:

Fluarix Quadrivalent, Fluzone Quadrivalent, FluLaval Quadrivalent, Afluria Quadrivalent, Fluzone High-Dose Quadrivalent, Flublok Quadrivalent

• 0.5 mL IM x1 dose/season

Fluad Quadrivalent

• Not indicated for adults below 65 years

Egg allergy

• The Advisory Committee on Immunization Practices (ACIP) recommends Flublok Quadrivalent for vaccination of persons with egg allergy of any severity
• Flublok Quadrivalent does not use the influenza virus or chicken eggs in its manufacturing process

Geriatric:

Indicated for use in patients 65 years or above

Afluria Quadrivalent, Fluzone Quadrivalent, FluLaval Quadrivalent, Fluad Quadrivalent,

• 0.5 mL IM x 1 dose/season

Fluzone High-Dose Quadrivalent

• 0.7 mL IM x 1 dose/season

Pediatric:

Flublok

• Safety and efficacy not established for pediatric use (below 18 years)

Fluarix Quadrivalent, Afluria Quadrivalent, FluLaval Quadrivalent, or Fluzone Quadrivalent

Children below 6 months

• Safety and efficacy not established

Children 6 months up to 9 years

• Fluarix Quadrivalent
  • Not previously vaccinated: 0.5 mL IM x 2 doses
  • Previously vaccinated in a previous season: 0.5 mL IM x 1-2 doses
• Afluria Quadrivalent, FluLaval Quadrivalent, or Fluzone Quadrivalent
  • Children 6 to 36 months and not previously vaccinated: 0.25 mL or 0.5 IM x 2 doses
  • Children 6 to 36 months and previously vaccinated in a previous season: 0.5 mL IM x 1-2 doses
  • Children 36 months to 9 years and not previously vaccinated: 0.5 mL IM x 2 doses
  • Children 36 months to 9 years and previously vaccinated in a previous season: 0.5 mL IM x 1-2 doses
  • Flucelvax Quadrivalent
  • Children 4 to 9 years: 0.5 mL 1-2 doses

Children 9 years or above

• For all formulations
• 0.5 mL IM x 1 dose

Dosing Considerations

Contains the following 4 viral strains for the 2022-2023 Northern Hemisphere season

• A/Victoria/2570/2019 (H1N1)pdm09-like virus (no change from last season)
• A/Darwin/9/2021 (H3N2)-like virus (new for 2022-2023)
• B/Austria/1359417/2021 (B/Victoria lineage)-like virus (new for 2022-2023)
• B/Phuket/3073/2013-like virus (B/Yamagata lineage) (no change from last season)

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 the influenza virus vaccine include:
  • ifosfamide
  • ustekinumab
• The influenza virus vaccine has serious interaction with at least 96 different drugs.
• The influenza virus vaccine has serious interaction with at least 50 different drugs.
• Mild interactions of influenza virus vaccine include:
  • amantadine
  • ethotoin
  • fosphenytoin
  • ozanimod
  • phenytoin

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 studies showed no evidence of fetal harm with flu vaccination during pregnancy.
• Pregnant women are at a higher risk than non-pregnant women for influenza-related complications. Pregnant women who contract influenza may be at an increased risk for preterm labor and delivery.
• FluMist Quadrivalent live attenuated nasal spray vaccine should not be used in pregnant women.
• Fluad Quadrivalent is approved only for people older than 65 years of age.
• There are no data on the presence of the influenza virus vaccine in breastmilk, or its effect on milk production or on the breastfed infant. The decision to breastfeed should be made after considering the developmental and health benefits of breastfeeding, along with the potential adverse effects on the infant from the vaccine or the mother’s susceptibility to contracting flu infection.
• There is a pregnancy exposure registry that monitors pregnancy outcomes in women following influenza virus vaccination during pregnancy. Healthcare providers are encouraged to enroll women by contacting:
  • FluLaval Quadrivalent, Fluarix Quadrivalent: 1-888-452-9622
  • Afluria Quadrivalent: 1-855-358-8966 or send an email to Seqirus at [email protected]
  • Fluzone Intradermal Quadrivalent or Fluzone Quadrivalent: Sanofi Pasteur Inc at 1-800-822-2463
  • Flublok Quadrivalent: Protein Sciences Corporation 1-888-855-7871

• All flu vaccines for the 2022-2023 season are quadrivalent vaccines, designed to protect against four different flu viruses, including two influenza A viruses and two influenza B viruses.
• Centers for Disease Control and Prevention (CDC) recommends all people 6 months and older to get a flu vaccine every year, and there are many flu vaccine options to choose from.
• For more information, visit https://www.cdc.gov/flu/prevent/flushot.htm