Recent developments in the understanding of the structure and replicat
ions of a wide range of pathogens, including viruses, bacteria and par
asites have opened up ways of designing novel vaccines which should bo
th improve the quality and extend the range and value of vaccines as m
ajor prophylactic and therapeutic tools of the future. Two main strate
gies have emerged, one involving the development of synthetic vaccines
which are essentially composed of selected epitopes of the pathogenic
agent that will elicit neutralising antibodies. The other strategy at
tempts to make use of chimeric agents that will allow live virus or ba
cteria to be used as vectors for carrying appropriate epitopes of the
target pathogen. Current knowledge about the immunology and improvemen
ts in the presentation of antigen to the immune system will also play
an important role in the rational design of vaccines. This review summ
arises present methods of producing vaccines and considers the develop
ment of more rational methods of vaccine design that will greatly infl
uence the production of vaccines in the future.