Prevalence and Genetic Diversity of Group A Rotavirus in Children Under Five Years, before and after Vaccine Introduction at Mukuru Informal Settlements, Nairobi County, Kenya Regina Wamuyu

Abstract

Rotavirus vaccines have been shown to be a lifesaving and cost-effective public health intervention in Africa and have resulted in reduced rotavirus mortality. In Kenya, rotavirus diarrhea causes 19% of hospitalizations and 16% of clinic visits among children <5 years of age and causes 4471 deaths and 8,781 hospitalizations per year. The aim of this study was to compare the prevalence and molecular characterization of Group A rotavirus in pre- and post-vaccine period in children less than five years attending Mukuru informal settlements clinic Nairobi County. A total of 270 stool samples (150 pre-vaccine and 120 post-vaccine) were tested for rotavirus using ELISA Prospect kit (Oxoid Ltd UK), sequenced partially for VP4 and VP7 and data analyzed using SPSS version 20. Sequences were assembled using Sequencer software, aligned using MAFFT and phylogenetic trees were constructed using MEGA version 5.2. For the vaccine coverage, data proportions for the children vaccinated was retrieved from immunization clinics record books and entered into excel for analysis. The results showed that rotavirus was more prevalent before vaccine introduction in children <12 months 6/36 (16.7%) compared to after vaccine introduction (P<0.05; χ2=6; df =1) and 13-24 months 4/42 (9.5%) (P<0.05; χ2=9.6; df =1). In children 25-36 months and 37- 48 months however, there was no significance difference in prevalence of rotavirus infection pre-and post-vaccine introduction (P>0.05; χ2=0.5; df =1) and (P>0.05; χ2=0.184; df =1) respectively. The prevalence of rotavirus infection detected in female was 8/75 (10.7%) compared to male 7/75 (9.3%) for the period before vaccine however, this was not statically significant. For the period after vaccine introduction cases in male were higher 4/64 (6.3%) compared to female 2/56 (3.6%). Overall, rotavirus prevalence was 10% (15/150) and 5% (6/120) in pre-vaccine and post-vaccine samples respectively. The major genotype combination both before vaccine and after vaccine was G1P [8] followed by G9P[8]. Other uncommon strains circulating in Mukuru informal settlement after vaccine introductions include G2 [P4], G3[P4], G4[P4]. The proportion of children vaccinated in Mukuru with rotavirus vaccine was 80.3% in the first year of vaccine xix introduction. There was significant statistical difference in rotavirus prevalence for cases less than 12 months of age, 13-24 months and over 49 months pre-and post-vaccine introduction. However, no significant difference in prevalence for age category 25-36 and 37- 48 months thus the vaccine proved to have a significant protection in the most vulnerable group of children. In conclusion, this study showed a reduction in prevalence of Group A rotavirus in Mukuru selected clinics one year after vaccine introduction into National Immunization program in Kenya.