Adjuvants are added to many vaccines to increase their immunogenicity and efficacy. Aluminium salts (alum) have been widely used as adjuvants and are generally considered safe.

Aluminium salts however have their limitations in terms of adjuvant effect, and a wide range of novel adjuvants are now being evaluated for use in new or improved vaccines. These adjuvants include immunostimulators, microparticulate carriers and emulsions as well as various combinations of these. It is hoped that these adjuvants could permit the development of safe and efficacious vaccines against diseases for which we do not yet have vaccines, such as malaria and HIV, and also to improve the efficacy of other vaccines. Since many of the new adjuvants are likely to be used for the first time in vaccines for diseases endemic in developing countries, systems for safety monitoring of these novel vaccines will be required in these countries.

The Global Advisory Committee on Vaccine Safety has discussed the safety of adjuvants in general on a number of occasions. Specifically, it has discussed a potential association between aluminium-containing vaccines and macrophagic myofasciitis and the safety of squalene in squalene-based adjuvants.