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

Influvac is an inactivated influenza vaccine indicated for the prevention of influenza caused by influenza A and B viruses.

• Seasonal influenza (A and B): provides protection against circulating strains, reducing the risk of infection and associated complications.
• Elderly and individuals with chronic conditions: lowers incidence of severe influenza disease and hospitalisation.
• Children 6 months to 5 years: supports immune protection during the flu season.
• Pregnant women: helps prevent influenza‑related morbidity for mother and fetus.
• Healthcare workers: reduces transmission risk in clinical settings.

• Influvac contains purified hemagglutinin and neuraminidase antigens from the selected influenza A (Victoria) and influenza B (Austria/2021‑like) strains. After intramuscular or subcutaneous injection, these viral proteins are taken up by antigen‑presenting cells, which display them to T‑lymphocytes, stimulating a B‑cell response that produces strain‑specific antibodies. The resulting humoral immunity neutralises the virus upon exposure, preventing infection. Memory B cells generated by the vaccine provide longer‑term protection for subsequent flu seasons.

Influvac, like other inactivated influenza vaccines, may be associated with local and systemic reactions following injection.

Common Side Effects

• Injection site pain: mild to moderate soreness at the injection site.
• Redness or swelling: transient erythema or edema around the site.
• Low‑grade fever: temperature up to 38 °C within 24 hours.
• Headache: mild headache occurring shortly after vaccination.
• Myalgia: muscle aches lasting one to two days.
• High fever: temperature above 39 °C, may need antipyretics.
• Severe local reaction: extensive swelling or necrosis.

Serious or Rare Side Effects

• Anaphylaxis: severe allergic reaction requiring immediate medical attention.
• Guillain‑Barré syndrome: rare neurological disorder that may develop within weeks.
• Seizures: infrequent occurrence, especially in children with fever.
• Severe allergic reaction: includes angioedema or bronchospasm.
• Persistent high fever: prolonged temperature elevation beyond 48 hours.

Before administering Influvac, healthcare professionals should observe the following precautions to ensure safe use.

• Allergy assessment: avoid vaccination in individuals with known hypersensitivity to any vaccine component.
• Acute illness: postpone vaccination if the person has moderate or severe fever or acute infection.
• Pregnancy: consult a healthcare provider; safety data are limited, use only if benefits outweigh risks.
• Immunocompromised patients: vaccine may be less effective; monitor immune response.
• Concomitant medications: avoid simultaneous administration of immunoglobulins or blood products that could interfere with antibody development.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Influvac may interact with certain agents that affect immune response or mask vaccine‑related symptoms.

Major Interactions (Avoid)

• Immunoglobulin therapy: may reduce vaccine‑induced antibody production.
• Live attenuated vaccines: avoid co‑administration within 4 weeks to prevent interference.

Moderate Interactions (Monitor Closely)

• Antipyretics (acetaminophen, ibuprofen): may alleviate fever but could blunt antibody response if taken prophylactically.
• Immunosuppressive drugs (corticosteroids, chemotherapy): may diminish vaccine efficacy.
• Antiviral agents (oseltamivir) given within 48 hours of vaccination: may interfere with immune response.