in areas of active and passive immunization as well as in stimulation of enhanced nonspecific resistance .. Progress in the field of infectious diseases can be accelerated when a generation of new improved vaccines are developed. These vaccines should be capable of activat­ ing the cellular and the humoral immune responses as well as inducing persistent immunological memory. Development of novel regimens for enhancing natural resistance against infections is also progressively gaining in importance. The urgency increases as chemotherapy against viral and other infections further continues to be plagued by a carousel of a limited number of licensed drugs, problems of side effects, and development of drug resistance. It is becoming expedient that future strategies embrace a policy directed towards triggering mechanisms capable of inducing specific and nonspecific host defences.