EVALUATION OF 2 LIVE, COLD-PASSAGED, TEMPERATURE-SENSITIVE RESPIRATORY SYNCYTIAL VIRUS-VACCINES IN CHIMPANZEES AND IN HUMAN ADULTS, INFANTS, AND CHILDREN

Two live-attenuated, cold-passaged (cp), temperature-sensitive (ts) ca ndidate vaccines, designated cpts530/1009 and cpts248/955, were attenu ated, genetically stable, and immunogenic in chimpanzees and were high ly attenuated for human adults, In respiratory syncytial virus (RSV)-s eropositive children, cpts530/1009 was more restricted in replication than cpts248/955. In seronegative children, 10(4) pfu of cpts248/955 w as insufficiently attenuated, and a high titer of vaccine virus was sh ed (mean peal; titer, 10(4.4) pfu/mL), whereas 10(4) pfu of cpts530/10 09 was relatively attenuated and restricted in replication (mean peak titer, 10(4) pfu/mL), At a dose of 10(5) pfu, cpts530/1009 was immunog enic in seronegative children (geometric mean titer of RSV neutralizin g antibodies, 1:724), Transmission of either vaccine to seronegative p lacebo recipients occurred at a frequency of 20%-25%. Of importance, v accine viruses recovered from chimpanzees and humans were ts, In contr ast to previous studies, this study indicates that live attenuated RSV vaccines that are immunogenic and phenotypically stable can he develo ped, Additional studies are being conducted to identify a live RSV vac cine that is slightly more attenuated and less transmissible than cpts 530/1009.