Impact and effectiveness of Rotavin-M1 under conditions of routine use in two provinces in Vietnam, 2016-2021, an observational and case-control study

Abstract

Background: Half of diarrhea hospitalizations in children aged <5 years in Vietnam are due to rotavirus. Following introduction of a locally developed and licensed oral rotavirus vaccine, Rotavin-M1, into the routine immunization program in two Vietnamese provinces, Nam Dinh and TT Hue, we describe changes in rotavirus positivity among children hospitalized for diarrhea and calculate vaccine effectiveness against moderate-to-severe rotavirus hospitalizations.

Methods: Active rotavirus surveillance among children <5 years began in December 2016 at sentinel hospitals in districts where rotavirus vaccine was introduced in December 2017. To estimate reductions in rotavirus detection, we calculated risk ratios comparing rotavirus positivity pre- and post-vaccine introduction. We used a test-negative case-control design to calculate vaccine effectiveness.

Findings: From December 2016 to May 2021, 7228 children <5 years hospitalized for diarrhea were enrolled. Following introduction, Rotavin-M1 coverage was 77% (1066/1377) in Nam Dinh and 42% (203/489) in TT Hue. In Nam Dinh, rotavirus positivity among children <5 years significantly declined by 40.6% (95% CI: 34.8%-45.8%) during the three-year post-vaccine introduction period. In TT Hue, no change in rotavirus positivity was observed. Among children aged 6-23 months, a 2-dose series of Rotavin-M1 was 57% (95% CI: 39%-70%) effective against moderate-to-severe rotavirus hospitalizations.

Interpretation: Higher vaccination coverage in Nam Dinh than TT Hue likely contributed to substantial declines in rotavirus positivity observed in Nam Dinh following rotavirus vaccine introduction. Robust vaccine effectiveness was observed through the second year of life. National rotavirus vaccine introduction with high coverage may have substantial impact on reducing rotavirus disease burden in Vietnam.

Funding: Bill and Melinda Gates Foundation.

Keywords: Rotavirus; Rotavirus vaccine; Vaccine effectiveness; Vietnam.

Fig. 1

a) Number of rotavirus positive and negative children <5 years of age hospitalized for rotavirus diarrhea, proportion rotavirus positive and proportion vaccinated, b) Rotavirus positivity by age and rotavirus season, c) Number of rotavirus hospitalizations by age and rotavirus season, and d) distribution of diarrhea severity by season, Nam Dinh Province, December 2016–May 2021.

Fig. 2

Distribution of circulating rotavirus genotypes among children <5 years of age by rotavirus season in a) Nam Dinh Province, April 2017–March 2021 and b) TT Hue Province, January 2017–December 2020.

Fig. 3

a) Number of rotavirus positive and negative children <5 years of age hospitalized for rotavirus diarrhea, proportion rotavirus positive and proportion vaccinated, b) Rotavirus positivity by age and rotavirus season, c) Number of rotavirus hospitalizations by age and rotavirus season, and d) distribution of diarrhea severity by season, TT Hue Province, December 2016–December 2020.

Fig. 4

Rotavirus vaccine effectiveness and 95% confidence intervals∗ among children 6–23 months of age by Vesikari score, Nam Dinh and TT Hue Provinces, 2017–2021. ∗The gray diamonds represent the vaccine effectiveness estimate and the lines are the 95% confidence interval.