The Impact of Improved Water, Sanitation, and Hygiene on Oral Rotavirus Vaccine Immunogenicity in Zimbabwean Infants: Substudy of a Cluster-randomized Trial

Abstract Background Oral vaccines have lower efficacy in developing compared to developed countries. Poor water, sanitation, and hygiene (WASH) may contribute to reduced oral vaccine immunogenicity. Methods We conducted a cluster-randomized 2 × 2 factorial trial in rural Zimbabwe. Pregnant women and their infants were eligible if they lived in clusters randomized to (1) standard of care (52 clusters); (2) improved infant feeding (53 clusters); (3) WASH: ventilated improved pit latrine, 2 hand-washing stations, liquid soap, chlorine, infant play space, and hygiene counseling (53 clusters); or (4) feeding plus WASH (53 clusters). This substudy compared oral rotavirus vaccine (RVV) seroconversion (primary outcome), and seropositivity and geometric mean titer (GMT) (secondary outcomes), in WASH vs non-WASH infants by intention-to-treat analysis. Results We included 801 infants with documented RVV receipt and postvaccine titer measurements (329 from 84 WASH clusters; 472 from 102 non-WASH clusters); 328 infants with prevaccination titers were included in the primary outcome. Thirty-three of 109 (30.3%) infants in the WASH group seroconverted following rotavirus vaccination, compared to 43 of 219 (19.6%) in the non-WASH group (absolute difference, 10.6% [95% confidence interval {CI}, .54%–20.7%]; P = .031). In the WASH vs non-WASH groups, 90 of 329 (27.4%) vs 107 of 472 (22.7%) were seropositive postvaccination (absolute difference, 4.7% [95% CI, –1.4% to 10.8%]; P = .130), and antirotavirus GMT was 18.4 (95% CI, 15.6–21.7) U/mL vs 14.9 (95% CI, 13.2–16.8) U/mL (P = .072). Conclusions Improvements in household WASH led to modest but significant increases in seroconversion to RVV in rural Zimbabwean infants. Clinical Trials Registration NCT01824940. Oral vaccines have lower efficacy in developing compared to developed countries. In a substudy of a cluster-randomized trial, improvements in household water, sanitation, and hygiene led to modest increases in seroconversion to oral rotavirus vaccine among rural Zimbabwean infants.