Rotavirus Strain Distribution before and after Introducing Rotavirus Vaccine in India

Abstract

In April 2016, an indigenous monovalent rotavirus vaccine (Rotavac) was introduced to the National Immunization Program in India. Hospital-based surveillance for acute gastroenteritis was conducted in five sentinel sites from 2012 to 2020 to monitor the vaccine impact on various genotypes and the reduction in rotavirus positivity at each site. Stool samples collected from children under 5 years of age hospitalized with diarrhea were tested for group A rotavirus using a commercial enzyme immunoassay, and rotavirus strains were characterized by RT-PCR. The proportion of diarrhea hospitalizations attributable to rotavirus at the five sites declined from a range of 56-29.4% in pre-vaccine years to 34-12% in post-vaccine years. G1P[8] was the predominant strain in the pre-vaccination period, and G3P[8] was the most common in the post-vaccination period. Circulating patterns varied throughout the study period, and increased proportions of mixed genotypes were detected in the post-vaccination phase. Continuous long-term surveillance is essential to understand the diversity and immuno-epidemiological effects of rotavirus vaccination.

Keywords: Rotavac vaccine; rotavirus diarrhea; rotavirus genotyping.

Figure 1

Impact of rotavirus vaccine after its introduction into the universal immunization programme in India, pre-vaccination and post-vaccination introduction surveillance comparison data from study sites at Rohtak (A), Tandak (B), Tirupati (C) Bhubaneswar (D), Vellore (E), and all the sites combined (F).

Figure 2

Data represented as the proportion of a specific genotype compared to the total genotype results. Uncommon genotype: <1% of total results; Mixed genotypes: those with >1 G or P-type; Untypables: those with either G or P untyped.

Figure 3

Comparison of genotype distribution between Northern sites (Tanda and Rohtak) and Southern sites (Vellore, Tirupati and Bhubaneswar). The major genotypes are compared during pre-vaccination (September 2012–April 2016) and post-vaccination period (May 2016–June 2020). The mixed genotype infections were excluded from the analysis.