Potential of attenuated respiratory syncytial virus vaccine for infants and children.

Respiratory syncytial virus (RSV) disease is a major cause of death and hospitalization in infancy and a frequent cause of morbidity throughout childhood. Serum antibody does not protect as is evident from the study of natural disease and use of killed vaccines. Local antibody responses occur in natural illness. Possibly serum antibody in the absence of local antibody plays a part in illness. We have studied local and serum antibody response to potential attenuated vaccines: a 26 degrees C adapted RSV and a ts mutant RSV. Both produced the desired infection as evidenced by virus recovery, serum and local antibody response. However, both appear to have had residual pathogenicity for young infants. This included mild bronchitis after the 26 degrees C RSV and mild rhinitis, which might be acceptable, but also fever and otitis in one infant after the ts RSV. Also, some of the virus recovered in the ts studies had wild type characteristics. An acceptable RSV vaccine strain will (a) infect without undergoing reversion or other genetic changes, (b) induce resistance to wild type virus, (c) cause no or very mild inflammatory changes such as the rhinitis associated with the vaccines thus far tried.