Evaluation of a live, attenuated respiratory syncytial virus vaccine in infants.

Respiratory syncytial virus ts-1 is a live attenuated experimental vaccine which was administered intranasally to 25 infants 11 to 19 months of age. Clinical evaluation was carried out following a controlled, double-blind protocol which eliminated observer bias, assessed intercurrent illness, and was designed to detect virus transmission. At the low dose of virus of virus used (100 TCID50) 8 of the 25 recipients were successfully infected with RS virus ts-1 as determined by virus shedding or antibody response.