In November 2015, FDA licensed Fluad (aIIV3, CSL Seqirus), a trivalent, MF59-adjuvanted inactivated influenza vaccine, for people age 65 years and older. Fluad is now quadrivalent (aIIV4). Fluad is the first adjuvanted influenza vaccine marketed in the U.S. An adjuvant is a substance added to a vaccine to increase the immune response to vaccination. The MF59 adjuvant is based on squalene, an oil that occurs naturally in many plants and animals. Fluad has been used in Europe since 1997 and is approved in many other countries. In contrast to Fluzone High-Dose Quadrivalent (Sanofi), Fluad is a standard-dose vaccine, containing 15 mcg of hemagglutinin per virus per dose.