Is Efluelda an Inactivated Vaccine?
Yes, Efluelda (Fluzone High-Dose Quadrivalent) is an inactivated influenza vaccine specifically formulated for adults aged ≥65 years.
Vaccine Classification and Characteristics
Efluelda belongs to the category of high-dose inactivated influenza vaccines (HD-IIV). The vaccine viruses are made noninfectious through an inactivation process, meaning they are killed viruses that cannot replicate or cause influenza infection 1.
Key Features of Efluelda
Inactivation Status: The vaccine contains killed influenza viruses that have been rendered noninfectious through chemical inactivation processes 1
Antigen Content: Efluelda contains 60 μg of hemagglutinin (HA) per vaccine virus strain (180 μg total in the quadrivalent formulation), which is four times higher than standard-dose vaccines that contain 15 μg per strain 1
Formulation: It is an egg-based vaccine, meaning the reference vaccine viruses are propagated in embryonated hens' eggs 1
Administration: Given as a 0.5-mL intramuscular injection 1
Manufacturing Process
The manufacturing of inactivated influenza vaccines like Efluelda involves:
- Growing vaccine viruses in embryonated hens' eggs 1
- Using chemical compounds to inactivate (kill) the influenza viruses 1
- Creating purified surface antigen preparations 1
- Adding antibiotics to prevent bacterial contamination during production 1
Clinical Distinction from Live Vaccines
Unlike live attenuated influenza vaccine (LAIV), which contains live viruses and is administered intranasally, Efluelda contains killed viruses and cannot produce signs or symptoms of influenza virus infection 1. This fundamental difference makes inactivated vaccines like Efluelda appropriate for elderly populations and those with chronic medical conditions, whereas LAIV is restricted to healthy persons aged 2-49 years 1, 2.
Approved Population
Efluelda is FDA-approved exclusively for persons aged ≥65 years, though it is also an acceptable option for solid organ transplant recipients aged 18-64 years receiving immunosuppressive medications 1.