Effectiveness Of Rotavirus Vaccine In Sub-sahara Africa:a Systematic Review And Meta-analysis

Background:Both monovalent(Rotarix(?),RV1)and pentavalent(RotaTeq(?),RV5)of group 'A' rotavirus(RVA)vaccine have been in the market since 2006.Most countries in sub-Saharan Africa have introduced RVA vaccines into their routine immunization.Although several studies have been conducted in some African countries,the immunological effects and persistence of both RVA vaccines have yet to be studied.Aim:This study seeks to assess RVA vaccine effectiveness and persistence in sub-Saharan Africa and also compare how significantly the effectiveness varies between the US and sub-Saharan Africa using system review and meta-analysis.Methods:We searched Medline(PubMed database),Scopus and Web of Science for rotavirus vaccination in the US and Sub-Sahara Africa from 2007 to 2017.Case control studies reporting outcome of rotavirus vaccine in children less than 5 was selected for inclusion.The methodological quality of our selected studies were assessed using the Newcastle-Ottawa scale 9(NOS)for observational studies in meta-analysis.Odds ratios(OR)and vaccine effectiveness were generated from pooled data on laboratory confirmed RVA cases of children less than 5 years using meta-analysis with random effects or fixed effect model.Sensitivity analysis and subgroup analysis were used.The publication bias was estimated by funnel plot.Results:For the US,60 articles from online databases met our eligibility criteria and after reviewing full texts,5 articles were used for our analysis.67 articles met our initial criteria and 6 case-control studies involving 5930 participants(1246 cases and 4684 control groups)were included in our final analyses in the sub-Sahara study.Pooled effectiveness of 3 doses of RV5 vaccine in the US recorded was 0.78(95%Cl:0.06 to 0.95)and pooled effectiveness of 2 doses of the RV1 vaccine recorded was 0.77(95%CI:0.58 to 0.97).In sub-Sahara Africa,pooled effectiveness of two doses of monovalent vaccine was 0.30(95%CI:0.19 to 0.40).For infants less than or equal to 12 months,the effectiveness was 0.29(95%CI:0.13 to 0.42);and 0.37(95%Cl:0.04 to 0.58)was for infants greater than 12 months.Effectiveness for vesicari score>11 ranged from 0.22 to 0.97 and 0.36 to 0.44 for vesicari score>15.RVA vaccine shows protection against severe diarrhea-related hospitalizations in sub-Saharan African countries.Effectiveness was a little higher among infants 12 months and above than among infants less than 12 months.The effectiveness also showed no significant difference between unexposed uninfected HIV infants and exposed but uninfected HIV infants.Rotavirus vaccine is effective in reducing rotavirus hospitalization in infants in sub-Sahara Africa and our meta-analysis shows a sustained effectiveness through the second year of life as well as effectiveness in HIV exposed but uninfected children.There is also the reduction of the severity of rotavirus infection.Our study depended on secondary data on published works that satisfies particular selection criteria.We could not do meta-analysis for RV5 vaccine since only one country has performed an effectiveness study in Sub-Sahara Africa as at the time of our research and that study was sponsored by the vaccine manufacturer.Another limitation could be the selection of only case-control studies.The selection of controls from studies was assessed with the Newcastle Ottawa Score(NOS)with good score but it is also possible that it did not identify the study design weaknesses especially in the area of the control selection.There were publication biases in most studies.Conclusions:Our findings were statistically significant and further studies are needed to firmly establish the findings of this study,especially for long-time prospective clinical studies.