influenza vaccine (high-dose)

Influenza vaccine (high-dose), marketed primarily under the brand name **Fluzone High-Dose** (and **Efluelda** in Europe), is an inactivated, split-virion biologic vaccine developed by Sanofi Pasteur. It is specifically formulated for adults aged 65 and older, a population that often exhibits a diminished immune response to standard-dose vaccines due to immunosenescence. The vaccine contains 60 micrograms (mcg) of hemagglutinin (HA) antigen per virus strain—four times the concentration found in standard-dose influenza vaccines (15 mcg per strain). By providing a higher antigen load, the vaccine stimulates a more robust production of hemagglutination-inhibition (HAI) antibodies. It is produced using embryonated chicken eggs and is available in quadrivalent formulations targeting two influenza A subtypes (H1N1 and H3N2) and two influenza B lineages (Victoria and Yamagata). Clinical trials have demonstrated that the high-dose formulation is significantly more effective than standard-dose vaccines at preventing laboratory-confirmed influenza in the elderly population.

Brand names

Fluzone High-DoseEflueldaFluzone High-Dose Quadrivalent

Other names

TIV-HDQIV-HDhigh-dose influenza vaccineinfluenza vaccine (surface antigen, inactivated, high-dose)