Epidemiology of rotavirus in Southern Vietnam : results of a sentinel surveillance from 2013 to 2018

Abstract

Rotavirus infects nearly every child by the age of 3–5 years and is the leading cause of severe, dehydrating diarrhea in children aged <5 years worldwide. In Vietnam, nearly haft of diarrhea-related deaths are accounted for Rotavirus; the country also had one of the highest Rotavirus hospitalization figures in South East Asia. The two Rotavirus vaccines (Rotarix and Rotateq) were licensed in the state and available in the private sector, as well as Rotavin-M1 - a local licensed vaccine. In 1998, the Rotavirus sentinel surveillance was initiated in Vietnam. This study aimed to describe the Rotavirus sentinel surveillance findings from 2013 to 2018, including epics profile, clinical features, and genotyping information among hospitalized children under five years of age. Methods: A hospital-based study was performed from the Rotavirus sentinel surveillance at Paediatric Hospital No.1 in Ho Chi Minh city, Vietnam. Data were collected from children between 0 and 59 months of age whose primary reason for hospitalization was acute watery diarrhea. Children were included in the vaccine effectiveness analysis (VE) if they were at least six months old at the time of notification. Results: During 2013-2018, of 5,179 acute diarrhea cases included in the study, Rotavirus was detected in 2,424 cases (46.80%), a downward trend was observed from 2013 (55.27%) to 2018 (43.54%). Dry season months (from November to April) witnessed a 2.4 times higher occurrence of Rotavirus positive cases compared to rainy season months (May to October) (OR=2.4, 95% CI: 2.14 - 2.692, p<0.001). The mortality rate was 0.04%. The typical symptoms associated with Rotavirus AGE were vomiting (present of vomiting, average max number per day, duration), dehydration status, present of fever, diarrhea (average max number per day) (p<0.05). Rotavirus AGE was more likely to be severe than the negative group (p<0.001). Of 1,107 Rotavirus positive cases had PCR isolated for genotyping, G3P[8] was the most common G-P combined genotype (43.18%), followed by G8P[8], G1P[8], G2P[4] (constituted 19.69%, 12.92%, and 12.83%, respectively). We observed an enormous genotyping shift from 2013 to 2018: G3P[8] became more frequent during 2014-2018, with the rise from 8.13% in 2013 to a peak of 60.65% in 2017, then decreased to 41.15% in 2018. In contrast, G1P[8] considerably dropped from 69.92% in 2013 to no case in 2018. There also occurred a change in G8P[8] and G2P[4] prevalence. From no case in 2013, G8P[8] leaped to a peak of 47.21% in 2016 and was the predominant genotype at that year, before went down to 23.92% in 2018. G2P[4] showed a slight upward trend from 2013 to 2014 (from 15.45% to 37.41%), then dropped to 0.43% in 2016, before went up to 16.27% in 2018. The percentage of vaccinees among the study population was meager (3.84%). Among children ≥ 6 months of age, getting a completed schedule of Rotavirus vaccine in general, and the Rotarix vaccine in particular, had vaccine effectiveness against Rotavirus AGE at 82.34% (95% CI: 70.33%-89.49%), and 85.90% (95% CI: 74.10%-92.30%), respectively. Rotarix VE for G3P[8] was 88.35% (95% CI: 52.50%-97.14%). Conclusions: The findings in our study suggested that Rotavirus infection was still a significant cause of acute watery diarrhea among hospitalized children younger than five years old in Vietnam. There is a need to consider the recommended vaccine to use in the National Immunization Program in the dramatic genotyping shift situation. In addition to monitoring genotypes, whole genomic characterization of circulating Rotavirus strains before and after vaccine introduction will help to assess the vaccines' efficacy.