Paper Information

Data on rotavirus-positive stool specimens among children age <5 years hospitalized with diarrhea in Blantyre, Malawi before (July 1997 - October 2012, n=1765) and after (November 2012 - October 2019, n=934) RV1 introduction were analyzed. Rotavirus G and P genotypes were assigned using reverse transcription polymerase chain reaction.

A rich rotavirus strain diversity circulated throughout the 22-year period; Shannon (H) and Simpson diversity (D) indices did not differ between the pre- and post-vaccine periods (H' p < 0.149: D' p < 0.287). Overall, G1 (n=268/924; 28.7%), G2 (n=308/924; 33.0%), G3 (n=72/924; 7.7%) and G12 (n=109/924; 11.8%) were the most prevalent genotypes identified following RV1 introduction. The prevalence of G1P[8] and G2P[4] genotypes declined each successive year following RV1 introduction, and were not detected after 2018. Genotype G3 re-emerged and became the predominant genotype from 2017. No evidence of genotype selection was observed seven years post-RV1 introduction.

Rotavirus vaccine (Rotarix®, RV1) has reduced diarrhea-associated hospitalizations and deaths in Malawi. We examined the trends in circulating rotavirus genotypes in Malawi over a 22-year period to assess the impact of RV1 introduction on strain distribution.

Rotavirus strain diversity and genotype variation in Malawi is likely driven by natural mechanisms rather than vaccine pressure.