The adjuvanted influenza vaccines with novel adjuvants: experience with the MF59-adjuvanted vaccine

Elderly people and subjects with underlying chronic diseases are at increas ed risk for influenza and related complications. Conventional influenza vac cines provide only limited protection in the elderly population. In order t o enhance the immune response to influenza vaccines, several adjuvants have been evaluated. Among these, an oil in water adjuvant emulsion containing squalene, MF59, has been combined with subunit influenza antigens and teste d in clinical trials in comparison with non-adjuvanted conventional vaccine s. Data from a clinical database of over 10 000 elderly subjects immunised with this adjuvanted vaccine (Fluad(R), Chiron Vaccines. Siena, Italy) demo nstrate that, although common postimmunisation reactions are more frequent in recipients of the adjuvanted vaccine, this vaccine is well tolerated, al so after re-immunisation in subsequent influenza seasons. Immunogenicity an alyses demonstrate a consistently higher immune response with statistically significant increases of postimmunisation geometric mean titres, and of se roconversion and seroprotection rates compared to non-adjuvanted subunit an d split influenza vaccines, particularly for the A/H3N2 and the B strains. The higher immunogenicity profile of the MF59-adjuvanted vaccine is maintai ned also after subsequent immunisations. An even higher adjuvant effect was shown in subjects with low pre-immunisation titre and in those affected by chronic underlying diseases. In conclusion, the addition of MF59 to subuni t influenza vaccines enhances significantly the immune response in elderly subjects without causing clinically important changes in the safety profile of the influenza vaccine. (C) 2001 Elsevier Science Ltd. All rights reserv ed.