Effect of dose and a comparison of measures of vaccine take for oral rhesus rotavirus vaccine

Abstract

Ninety-six healthy infants ages 2 to 5 months received rhesus rotavirus vaccine serotype 3 (RRV) as a single dose of 10(3), 10(4) or 10(5) plaque-forming units (pfu) in this double-blinded, placebo-controlled study. Half of the infants in each dose group were also randomized to receive either 30 ml of infant formula as buffer before vaccination or were vaccinated on an empty stomach. The incidence of fever, increased stool frequency and decreased activity level was consistently higher among infants who received RRV than those who received placebo. There was no consistent increase in incidence of symptoms as the dose of RRV was increased. Possible vaccine-related side effects were increased in older vaccinees and in those with higher pre-vaccination antibody titers. The seroconversion rate and pre to postvaccination antibody rise, evaluated by enzyme-linked immunosorbent assay and by plaque reduction neutralization, correlated well. The 10(5) and 10(4) pfu RRV dose produced significantly higher rates of seroconversion and higher antibody rises than did placebo (P less than 0.001 for 10(5) and P = 0.005 for 10(4]. The 10(3) pfu dose was no more immunogenic than placebo. In the 10(4) pfu dose group 73% of infants receiving formula as a "buffer" seroconverted compared with 36% of those not receiving formula; 63% of infants partially breast-fed or formula-fed seroconverted compared with 17% of those exclusively breast-fed. These differences in seroconversion rate were largely overcome by increasing the RRV dose to 10(5) pfu. Stool (copro IgA) antibody responses were examined; of six infants showing a copro IgA response only one had seroconverted based on enzyme-linked immunosorbent assay or plaque reduction neutralization. RRV was recovered by tissue culture more frequently from the stool in those infants who received RRV 10(5) and 10(4) pfu than among those receiving 10(3) pfu or placebo (P less than 0.001).