Influenza virus inactivated split (H1N1, H3N2-like, b/brisbane/60/2008-like, strains): clinical use

Prescribing considerations

• Confirm that the current seasonal formulation follows official vaccination recommendations.
• Postpone vaccination during an acute febrile illness until the fever resolves.
• Assess bleeding risk before intramuscular administration in thrombocytopenia or coagulation disorders.
• Have facilities and trained staff available to manage anaphylaxis and prevent injury from syncope.
• Record the product name and batch number.

Contraindications and cautions

• The SmPC contraindicates use after hypersensitivity to active substances, excipients or trace manufacturing residues, including egg proteins, neomycin, formaldehyde or octoxinol-9.
• Previous confirmed anaphylaxis to an influenza vaccine requires specialist assessment. Egg allergy alone is not a contraindication under current programme guidance, but product-specific hypersensitivity labelling still applies.

Monitoring

• Observe for immediate hypersensitivity or syncope.
• Provide safety-netting for severe allergy or neurological symptoms.
• Consider whether immunosuppressive treatment could reduce vaccine response; routine antibody testing is not established as a measure of individual protection.

Clinical pharmacology

Inactivated split-virus antigens induce haemagglutinin-directed antibodies against included influenza strains. Maternal antibodies transferred across the placenta provide passive infant protection.

Formulation and product differences

• Vaxigrip is an egg-propagated trivalent suspension in a single-use pre-filled syringe.
• Presentations may have an attached, separate or safety needle, or no supplied needle; not all pack types are marketed.
• The suspension may contain trace egg proteins, neomycin, formaldehyde and octoxinol-9.
• Influenza strains change between seasons, so current product documentation and programme recommendations should be checked.