Adjuvant influenza vaccines.

Emulsified inactivated influenza vaccines have been in use for some 18 years and the goal of enhanced serological response lasting 2 years or more has been attained. The safety of the method in relation to immediate pyrogenic reactions has been demonstrated and no carcinogenic effects are known to have occurred in man. However, the problem of delayed local reactions after the injection of mineral-oil vaccines has not been solved. British experience of adverse reactions to commercial adjuvant influenza vaccine is quoted.New methods for obtaining adjuvant action without the risk of local abscess formation are needed both for inactivated whole virus and for split haemagglutinin vaccines. Reversal of water-in-mineral-oil emulsion to oil-in-water emulsion reduces viscosity and permits diffusion of the depot injection. A trial in Britain has shown equally good adjuvant properties of the reversed emulsion incorporating influenza virus vaccine so far as serological response is concerned, although it has not yet been conducted on a scale that would allow of adequate evaluation of the likelihood of delayed local reactions.