Influvac (Influenza Virus B/Austria/1359417/2021-Like Strain (B/Austria/1359417/2021, Bvr-26), Influenza A/Vic)

Influvac is used to prevent influenza infection caused by influenza A and B viruses.

• Seasonal influenza: reduces the risk of acquiring laboratory‑confirmed influenza illness.
• Influenza A infection: provides immune protection against circulating A subtypes such as A/Vic.
• Influenza B infection: induces antibodies targeting B lineage strains including B/Austria/1359417/2021.
• High‑risk populations: helps lower incidence of flu complications in elderly and immunocompromised individuals.

• Influvac contains inactivated whole‑virus particles of influenza A and B strains. After intramuscular or subcutaneous injection, the viral antigens are taken up by antigen‑presenting cells, which process hemagglutinin and neuraminidase proteins. This triggers activation of helper T cells and B cells, leading to production of strain‑specific neutralising antibodies that confer active immunity against subsequent exposure to the matched influenza viruses.

Common and rare adverse reactions may occur following administration of Influvac.

Common Side Effects

• Injection site pain: mild to moderate soreness at the site of injection.
• Redness or swelling: localized erythema or edema that resolves within a few days.
• Low‑grade fever: transient temperature rise usually below 38 °C.
• Headache or myalgia: mild muscular aches or headache lasting 1‑2 days.

Serious or Rare Side Effects

• Anaphylaxis: severe allergic reaction requiring immediate medical intervention.
• Guillain‑Barré syndrome: rare neurologic disorder characterized by progressive muscle weakness.
• Seizures: infrequent occurrence of convulsive episodes post‑vaccination.

Before administering Influvac, consider the following precautions to ensure safe use.

• Contraindication: avoid use in individuals with known severe allergy to any vaccine component.
• Prior severe reaction: defer vaccination in persons who experienced anaphylaxis after a previous influenza vaccine.
• Immunocompromised patients: assess risk‑benefit as response may be reduced.
• Acute illness: postpone vaccination until recovery from moderate or severe febrile illness.
• Pregnancy and lactation: discuss potential benefits and risks with a healthcare professional.
• Store at 2‑8 °C: keep refrigerated, protect from light, do not freeze or shake.

Vaccines can interact with certain medicines or biologics; relevant interactions for Influvac are listed below.

Major Interactions (Avoid)

• Live attenuated vaccines: should not be administered concurrently; separate by at least 4 weeks.
• Immunoglobulin or blood products: may diminish vaccine efficacy if given within 2 weeks before or after vaccination.

Moderate Interactions (Monitor Closely)

• Antipyretics (e.g., acetaminophen, ibuprofen): may reduce antibody response if taken prophylactically; use only for symptomatic relief.
• Immunosuppressive therapy (e.g., high‑dose steroids, chemotherapy): may impair immune response, consider timing vaccination before treatment.
• Antiviral medications (e.g., oseltamivir): generally safe but monitor for any alteration in vaccine effectiveness.