Virosomes as carriers for combined vaccines.

Immunopotentiating reconstituted influenza virosomes (IRIV) are liposomes which carry the two glycoproteins of the influenza virus on their surface. A hepatitis A vaccine using IRIV as carrier has very good immunogenicity and is well tolerated. The objective of this study was to produce a fivefold combined vaccine against hepatitis A and B, diphtheria, tetanus and influenza A/B, and to show that in principle IRIVs can serve as carriers for multiple antigens which have good immunogenicity and are well tolerated. A total of four studies were carried out. Either the combined vaccine or the corresponding adequately tested alum-adsorbed single vaccines were tested for reactogenicity and immunogenicity in young adults. A hepatitis A and B combination on an IRIV base showed the same immunogenicity and toleration as the single vaccines. However, with the simultaneous coupling of all five vaccines on the same IRIV or the binding of Di-Te and HAV on different IRIVs there was a suppression of the humoral immune response against HAV (p = 0.03). The possibility that epitope-specific suppression had occurred could be ruled out. The suppression of the response against HAV could be circumvented by halving the quantity of Di-Te antigen in the combined vaccine so as to avoid antigenic competition. Surprisingly, the immunogenicity of Di-Te vaccination in the combination proved superior to that of a separate vaccination. All vaccinations were well tolerated.