Safety and immunogenicity of an inactivated subunit influenza virus vaccine combined with MF59 adjuvant emulsion in elderly subjects, immunized for three consecutive influenza seasons.

A clinical trial to evaluate the safety and tolerability of a new influenza adjuvanted vaccine (FLUAD, Chiron Vaccines), compared with a conventional non adjuvanted influenza vaccine, was conducted in elderly ambulatory patients. Subjects were vaccinated with one dose of either vaccine each year for three consecutive years; 92 subjects received the first immunization, 74 subjects received the second and 67 subjects received the third. The primary objective of this study was to evaluate the safety of repetitive injections of the adjuvanted vaccine in elderly subjects. There were no reports of any vaccine-related serious adverse event or of safety concerns related to study vaccines after the first, second or third immunization. The adjuvanted vaccine induced more local reactions than the conventional vaccine; however, the reactions were normally mild and limited to the first 2-3 days after immunization. No statistically significant difference between groups in systemic postimmunization reactions was reported except for a mild, transient malaise after the first immunization. Compared with the first immunization, no increase in postimmunization reactions was seen after the second and third immunizations. Despite the small sample size of the trial, which was not powered to test immunogenicity differences, the antibody response was tested and resulted higher in the adjuvanted vaccine recipients, not only against the current season's vaccine strains, but also against heterologous vaccine strains.