[Perspectives on recombinant live vaccines].

Although vaccination has resulted in the reduction of diseases outbreaks, low levels of undesirable side effects are still a cause of concern. Traditional vaccines are made of live, attenuated, killed or fragmented pathogens, but recent progress in genetic engineering technique has enabled us to develop live attenuated mutants of several viruses and bacteria as potential vaccine vectors for antigen delivery. Such live vectors offer the advantage of delivery in a single oral, intranasal or inhalational dose, stimulating both systemic and mucosal immune responses. Here we describe the recent developments of new vaccines using recombinant viral and bacterial vectors.