Development of an adjuvant to enhance the immune response to influenza vaccine in the elderly.

Elderly persons typically show diminished immune responsiveness to influenza vaccination. Chiron Vaccines has developed a novel oil-in-water adjuvant emulsion, MF59, to enhance vaccine immunogenicity without compromising safety and tolerability. MF59 was shown to augment influenza vaccine immunogenicity in senescent mice. Subsequently, eight similarly designed, randomized, controlled clinical trials of a subunit influenza vaccine combined with MF59 were conducted between 1992 and 1995 in 1807 elderly volunteers (> or = 65 years old). Mild, transient, injection-site reactions were increased with MF59, but systemic reactions generally were not. For two of the three vaccine antigens (B and A/H3N2), postimmunization haemagglutinin inhibition geometric mean titres were statistically significantly higher with MF59. During influenza season, fewer deaths occurred among MF59 recipients. This development programme demonstrates how an adjuvant that stimulates effectors associated with immunosenescence can improve the performance of an existing vaccine in elderly persons.