Fractional dosing to improve vaccination coverage, vaccine hesitancy, and cost-effectiveness in Africa: a systematic review

BackgroundThe major challenges of vaccination programs are notably coverage in the target population, vaccine hesitancy, and cost-effectiveness. A vaccination strategy with fractional doses is a dose-saving strategy to address current vaccine shortages. Herein, we aimed to review the literature on administering fractional vaccine doses in Africa. MethodsA methodical search of PubMed was conducted to identify articles published up till March 31, 2023. Peer-reviewed studies were selected for inclusion if they focused on studies that described the use of fractional doses of vaccines and were conducted in any of the 54 African countries. ResultsFindings from eleven eligible studies were analyzed. Studies were from the Democratic Republic of the Congo, Gambia, Ghana, Kenya, South Africa, and Uganda. They covered five vaccines including the yellow fever vaccine (n=3; 27.3%), inactivated poliovirus vaccine (n=3; 27.3%), meningococcal A/C/Y/W135 vaccine (n=2; 18.2%), Haemophilus influenzae type b vaccine (n=2; 18.2%), and malaria vaccine (n=1; 9.1%). Fractionated doses used most often consist of one-fifth of the standard dose (n=8; 72.7%). Regarding immunogenicity/efficacity, eight of ten studies that addressed immunogenicity suggest that immune responses to the fractional dose vaccines were comparable to that of the standard dose vaccines and resulted in higher antibody titers. Regarding safety, all of the eight studies that addressed the safety of fractional doses in Africa, suggest that safety and tolerability data of fractional dosing were favorable compared to full dose regimen. ConclusionFractional dosing may be considered to address the availability and acceptability of certain vaccines while maintaining protection. This strategy also has the potential advantage of reducing the cost of vaccination programs, vaccine antigen overload, and vaccine side effects.