Asymptomatic Infections Due to Wild-Type Rotavirus May Prime for a Heterotypic Response to Vaccination with Rhesus Rotavirus

Variable homotypic and heterotypic protection has been observed following oral vaccination with rhesus rotavirus vaccine. Natural asymptomatic infections may enhance the efficacy of rhesus rotavirus vaccine. Asymptomatic seroconversion before and during the epidemic rotavirus season in Rochester, New York, was examined in a trial of 190 2- to 5-month-old infants receiving rotavirus and placebo vaccines. Six (37.5%) of 16 placebo recipients seroconverted; four of the six did so 2 to 8 months before the Rochester rotavirus season. Among the recipients of rotavirus vaccine, eight seroconverted before the rotavirus season as a consequence of asymptomatic infection. Four of the eight had not seroconverted after rotavirus vaccination, and four seroconverted from asymptomatic infection as well as from vaccination. Twelve rotavirus vaccinees had an asymptomatic seroconversion concurrent with the epidemic rotavirus season in Rochester: eight seroconverted following apparent vaccine failure, and four seroconverted following an apparent vaccine take. Six vaccinated infants with asymptomatic seroconversion during the rotavirus season had significant rises in the level of IgA antibody determined by ELISA, thereby suggesting preferential stimulation of memory cells of IgA. The possibility that variable heterotypic protection following oral rotavirus vaccination may be due to enhanced immunogenicity as a consequence of prior or concurrent infection with circulating wild-type rotaviruses appears to be supported by the findings of this report.