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

• Influvac Sub‑Unit is indicated for the prevention of influenza caused by circulating influenza A and B viruses.
• Seasonal influenza (A and B): reduces the incidence of laboratory‑confirmed influenza illness in vaccinated individuals.
• High‑risk groups (elderly, immunocompromised, chronic disease patients): lowers the risk of severe disease, hospitalization, and complications.
• Community outbreaks: contributes to herd immunity and helps limit spread of influenza within populations.

• The vaccine contains purified viral surface antigens from the selected influenza B/Austria/2021‑like strain and influenza A/Vic strain. After intramuscular or subcutaneous injection, these antigens are taken up by antigen‑presenting cells, processed, and displayed to T‑lymphocytes, prompting B‑cell activation and production of strain‑specific neutralising antibodies. The resulting humoral response equips the immune system to recognise and rapidly neutralise the corresponding influenza viruses upon exposure.

Influvac Sub‑Unit may be associated with a range of post‑vaccination reactions, most of which are mild and self‑limiting.

Common Side Effects

• Injection site pain: mild to moderate soreness at the injection site.
• Redness or swelling: localized erythema or edema.
• Low‑grade fever: temperature rise up to 38°C.
• Headache: transient headache.
• Myalgia: muscle aches.
• Fatigue: general tiredness.

Serious or Rare Side Effects

• Anaphylaxis: severe allergic reaction requiring immediate medical attention.
• Guillain‑Barré syndrome: rare neurological disorder with muscle weakness.
• Severe allergic reaction: urticaria, angioedema.
• Seizures: infrequent neurologic events.
• Thrombocytopenia: low platelet count.
• Acute respiratory distress: rare respiratory compromise.

Before administering Influvac Sub‑Unit, healthcare professionals should observe the following precautions.

• Allergy screening: avoid vaccination in individuals with known hypersensitivity to any vaccine component.
• Pregnancy considerations: assess risk‑benefit and consult obstetric guidance before use in pregnant women.
• Immunocompromised patients: vaccine may be less immunogenic; monitor response.
• Acute febrile illness: defer vaccination until the patient has recovered.
• Store at 2‑8°C: keep refrigerated, protect from light, do not freeze or shake.

Vaccination with Influvac Sub‑Unit may interact with other therapies; relevant interactions are listed below.

Major Interactions (Avoid)

• Live attenuated vaccines: concurrent administration may reduce efficacy of either vaccine.
• Immunoglobulin therapy: passive antibodies can neutralise vaccine antigens, diminishing response.
• Antiserum containing influenza antibodies: may interfere with active immunisation.

Moderate Interactions (Monitor Closely)

• Antipyretic or analgesic use: may mask fever but does not affect immunogenicity.
• Systemic corticosteroids: high‑dose steroids may blunt antibody production.
• Other inactivated vaccines: can be co‑administered at separate sites with routine monitoring.