New Vaccine Adjuvants and Other Excipients

Vaccine excipients (adjuvants and other substances used in the formulation) are treated in the same way as chemical substances. If new substances are introduced, a full safety assessment is required. It may be necessary to assess their toxic potential separately from the vaccine, since the vaccine formulation may interfere with a proper testing. In addition the normal pharmacological and safety tests for vaccines must be performed with the final, formulated product. 

For this reason vaccine formulation tends to follow the traditional routes innovative formulations are rare. Aluminium hydroxide, aluminium phosphate and calcium phosphate are still the only registered vaccine adjuvants for humans. Veterinary vaccines have to rely on the same components, however, a few vaccines containing a mineral oil adjuvant (Marcol) or saponin (Quil A or derivatives) have passed the registration hurdles. It remains to be seen whether and under which restrictions these adjuvants can be used in the EEC after 1996 (see also below in Additional requirements for veterinary products ). 

The implications of those safety requirements for urgently needed new adjuvants are significant. The adjuvant issue appears to be caught in a vicious circle. Risky vaccine projects cannot afford the extra risk and cost of an adjuvant development project, which could cost several million dollars. On the other hand, the success of several recombinant vaccines under development seems to depend on new and better adjuvants. The lack of clearly superior adjuvant candidates with reproducible effects aggravates this current situation. 

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