Many of the common respiratory illnesses of infancy and childhood are caused by 
viruses of the Paramyxoviridae family, in particular measles virus, respiratory 
syncytial (RS) virus and parainfluenzavirus type 3 (PI3). Effective measles 
vaccine was developed by classical methods, but these same methods have failed 
to provide vaccines to control RS and PI3 virus infections. The WHO Programme 
for Vaccine Development was initiated in 1983 to encourage the application of 
the new biotechnologies to continuing problems, such as the acute virus-induced 
respiratory diseases of childhood. At a meeting of research workers held in July 
1986 under the auspices of this programme, renewed optimism was expressed 
concerning the prospects for immunoprophylaxis of RS virus-induced disease. 
Animal models are now available for evaluation of the immunogenic potential of 
candidate vaccines. Vaccinia/RS recombinant viruses have been produced which 
have allowed the immunogenic properties of individual RS virus proteins to be 
defined. Complete protection without the exacerbation of disease, which earlier 
had accompanied the use of formalin-inactivated vaccines, has been achieved in 
animals immunized with vaccinia virus recombinants expressing the F protein; 
partial protection was obtained using G protein gene vectors. PI3 appears to be 
an inherently stable virus and evidence from animal experiments suggests that 
bovine PI3 might be suitable for use as a live vaccine in man.