Reactogenicity and immunogenicity of a high-titer rhesus rotavirus-based quadrivalent rotavirus vaccine.

We evaluated the reactogenicity and antigenicity of a quadrivalent rotavirus vaccine composed of serotype 3 rhesus rotavirus (RRV) and three single-gene-substitution reassortants of RRV and human strain D (D x RRV, serotype 1), DS1 (DS1 x RRV, serotype 2), or ST3 (ST3 x RRV, serotype 4) in a double-masked study with 302 infants in Caracas, Venezuela. Three doses of the quadrivalent vaccine composed of either 10(5) PFU (low titer) or 10(6) PFU (high titer) of each component were administered to 99 and 101 infants, respectively, at 4-week intervals starting at the second month of age; 102 infants received a placebo. Postvaccination reactions were monitored by home visits every other day during the week postvaccination. The vaccine was associated with the occurrence of mild, short-lived febrile episodes in 26 and 23% of the recipients after the first doses of high- or low-titer vaccine, respectively, in comparison with 13% of the infants receiving the placebo. Febrile reactions occurred less frequently in vaccinees after the second or third dose than after the initial dose. The vaccine was not significantly associated with diarrhea or any additional symptom or sign. Serum specimens obtained shortly before the first, 4 weeks after the first, and 4 weeks after the third dose of vaccine or placebo were tested by an immunoglobulin A enzyme-linked immunosorbent assay and by neutralization assays. Seroresponses occurred significantly more often after 3 doses than after a single dose of either vaccine. Immunoglobulin A responses were observed in 80 and 79% of the infants after 3 doses of high- or low-titer vaccine, respectively. Most of the infants tested developed a neutralization response to RRV after 3 doses of the high- (90%) or low-(88%) titer vaccine. Neutralization response rates to human rotavirus serotypes 1 to 4 after 3 doses were similar in both vaccine and 87 of 90 receiving the high-titer vaccine developed seroresponses, as detected by any of the assays employed. The study indicates that 3 doses of quadrivalent vaccine at a titer of 10(6) PFU of each component offered no advantage over the lower-titer preparation for use in efficacy trials.