SAFETY AND IMMUNOGENICITY OF A SUBUNIT RESPIRATORY SYNCYTIAL VIRUS-VACCINE IN CHILDREN 24 TO 48 MONTHS OLD

A subunit vaccine for respiratory syncytial virus (RSV) consisting of purified fusion glycoprotein (designated PFP-1) was tested in children 24 to 48 months old. Two doses of 20 mu g (n = 13) and 50 mu g (n = 1 0) were compared with a saline (n 24) placebo control group. Local and systemic reactions, reported within 96 hours postvaccination, were mi ld, transient, and did not differ significantly from the control cohor t. Long term follow-up through at least one, and in some cases two, RS V seasons showed no serious RSV illness in vaccinees at any time. Ther e was, therefore, no evidence of disease enhancement postvaccination. In the 20-mu g cohort, 92% responded to vaccination by a 4-fold increa se in enzyme-linked immunosorbent titer to the F glycoprotein and 42% had a 4-fold or greater rise in neutralizing titer to the A2 virus. In the 50-mu g cohort 100% responded by enzyme-linked immunosorbent to t he F glycoprotein and 70% responded by A2-neutralizing titers. The neu tralizing titers in the vaccinated cohorts were similar to those seen previously in adults. These data show the ability of the subunit vacci ne to boost existing immunity and to prime for a response to natural v irus exposure in children who were seronegative at the time of vaccina tion.