Circulation of Vaccine-derived Rotavirus G1P[8] in a Vulnerable Child Cohort in Rio De Janeiro.

BACKGROUND:The expansion of rotavirus (RV) immunization in several countries reduced the burden of acute diarrheal disease (ADD) and diarrhea-associated mortality. Although community transmission of live attenuated monovalent rotavirus vaccine (G1P[8] RV1) virus has been demonstrated in children and household contacts, fecal shedding of these strains in neonates and infants under six weeks of age has never been demonstrated. The objective of the study was to assess ADD and rotavirus vaccine strain shedding before and after immunization through 24 months of age.METHODS:This was a prospective cohort study in a low-resource community in which stool samples were collected from neonates from 15 to 45 days of age every 2 weeks, after both doses of G1P[8] RV1, and in subsequent ADD episodes until 2 years of age. RV was detected and genotyped in stool samples by RT-PCR.RESULTS:We enrolled 242 participants who were followed for an average of 23 months. The specific prevalence of G1P[8] RV1 virus was 3.3% in neonates and infants less than six weeks of age, 50% after the first dose, and 25.6% after the second dose. Among the 70 participants with ADD, G1P[8] RV1 virus was identified in only one participant (1.4% prevalence).CONCLUSIONS:In vaccinated children, there were no breakthrough infections with G1P[8] RV1 and ADD was rare supporting high vaccine effectiveness. We observed G1P[8] RV1 virus shedding among neonates and infants before the first vaccine dose, providing evidence of transmission of the vaccine strain from immunized children to those who are not yet vaccinated.