A Heterologous MF59-Adjuvanted H5N1 Prepandemic Influenza Booster Vaccine Induces a Robust, Cross-Reactive Immune Response in Adults and the Elderly

Immunogenicity and safety of a booster dose of an MF59-adjuvanted H5N1 vaccine containing 7.5 mu g A/turkey/Turkey/1/2005-like (clade 2.2) H5N1 hemagglutinin, given approximately 18 months after primary vaccination with a heterologous strain, were evaluated. The booster vaccine was well tolerated and induced a robust, cross-reactive immune response.