This invention relates to a novel immunoadjuvant, an adjuvant component, and vaccines containing the adjuvant component. The adjuvant includes phytol or a phytol derivative. The adjuvant component, when combined with a soluble or particulate antigen, provides a vaccine with an enhanced ability to induce both humoral and cytotoxic immune responses while displaying reduced toxicity and/or adverse side effects over vaccines that include the antigen but without the benefit of this adjuvant component.