SAFETY AND IMMUNOGENICITY OF ORAL TETRAVALENT HUMAN-RHESUS REASSORTANT ROTAVIRUS VACCINE IN NEONATES

We conducted a prospective randomized double blind study to determine: (1) the safety and immunogenicity of live oral tetravalent human-rhesus rotavirus reassortant vaccine in neonates; and (2) whether a second dose at the age of 6 to 8 weeks enhances the immunogenicity. Two hundred forty healthy neonates were enrolled and received vaccine (183) or placebo (57) on the second day of life. At the age of 6 to 8 weeks 133 received placebo and 88 received a second dose of vaccine. Medical events were noted within 10 days from vaccine administration in 6 of 183 (3.3%) vaccine recipients vs. 0 of 57 placebo recipients (P = 0.34) after the first dose and in 8 of 88 (9%) vs. 4 of 133 (3%) after the second dose (P = 0.069); none was severe and all were of short duration. Seroresponse of any type (detectable IgA or 4-fold increase of titer to rhesus rotavirus was 9% for the placebo, vs. 52 and 46% for those who received one and two doses of vaccine, respectively. However, neutralizing antibodies against human serotypes 1, 2 and 3 were not raised successfully in vaccinated infants when compared with placebo recipients. The same pattern was found when geometric mean titers were compared. Vaccine take was better when cord blood titers were low. At the age of 1 year the vaccinees had more often high titers for anti-rhesus rotavirus antibodies (> 640) than the placebo recipients (49% vs. 0%; P < 0.001). No difference was found between the groups in neutralizing antibodies to human serotypes 1, 2 and 3 rotavirus. We conclude that the vaccine is safe and moderately immunogenic in neonates. However, antibodies against human VP7 proteins did not achieve desirable levels and most of the response was to the VP4 proteins.