Immunopotentiating reconstituted influenza virosomes (IRIV) are efficient carrier systems for small virion particles such as hepatitis A virus (HAV).We evaluated immunogenicity and tolerability of an IRIV-HAV vaccine and the effectiveness of a booster by immunising 104 healthy HAV seronegative volunteers. A single dose was highly immunogenic, since 98% of volunteers had seroconverted after 2 weeks. Anti-HAV titres remained high, with 100% seroconversion rate 1 year later, when the booster was given. The vaccine was effective, with a 22-fold increase in geometric mean titres 1 month later. No serious adverse reactions were observed.