Differences of Rotavirus Vaccine Effectiveness by Country: Likely Causes and Contributing Factors

Abstract

Rotaviruses are a major cause of acute gastroenteritis in infants and young children worldwide and in many other mammalian and avian host species. Since 2006, two live-attenuated rotavirus vaccines, Rotarix® and RotaTeq®, have been licensed in >100 countries and are applied as part of extended program of vaccination (EPI) schemes of childhood vaccinations. Whereas the vaccines have been highly effective in high-income countries, they were shown to be considerably less potent in low- and middle-income countries. Rotavirus-associated disease was still the cause of death in >200,000 children of <5 years of age worldwide in 2013, and the mortality is concentrated in countries of sub-Saharan Africa and S.E. Asia. Various factors that have been identified or suggested as being involved in the differences of rotavirus vaccine effectiveness are reviewed here. Recognition of these factors will help to achieve gradual worldwide improvement of rotavirus vaccine effectiveness.

Prevalence and Genetic Diversity of Rotaviruses among under-Five Children in Ethiopia: A Systematic Review and Meta-Analysis

“…It is important to notice that the prevalence of G12P [8] rotavirus strains has increased globally [12,[35][36][37] in the post-vaccine introduction period, suggesting that they could have emerged as escape variants. The currently available vaccine in Ethiopia is a monovalent Rotarix vaccine that covers the G1P [8] strain; however, it may or may not provide sufficient protections against heterologous and the newly emerging rotavirus strains [14]. Hence, the development of new strain specific rotavirus vaccines for different regions based on surveillance data is crucial.…”

“…However, there is high genetic diversity of rotavirus strains circulating in Africa [13]. This G-P difference could be one of the reasons for variable efficacy of the available vaccines in different geographic locations [14]. Identification of the predominantly circulating genotypes of the rotavirus is essential to achieve optimal vaccine performance.…”

Effect of Aluminum Adjuvant and Preservatives on Structural Integrity and Physicochemical Stability Profiles of Three Recombinant Subunit Rotavirus Vaccine Antigens

“…2 Reasons behind the lower efficacy are multifactorial and not well understood. 3 There is thus a great need for a new-generation RV vaccine with enhanced efficacy for the developing world at affordable costs with consistent supply to improve vaccine coverage. 4 A trivalent subunit RV vaccine (nonreplicating rotavirus vaccine [NRRV]) contains 3 recombinant protein antigens (belonging to RV genotypes P [4], P [6], and P [8]; see next paragraph) and is currently in clinical trials in South Africa.…”

Recombinant Subunit Rotavirus Trivalent Vaccine Candidate: Physicochemical Comparisons and Stability Evaluations of Three Protein Antigens

“…In general, widely used RV vaccines (RotaTeq® and Rotarix®) show good efficacy (>85%) in developed countries, however, efficacy is reduced (40%-60%) in the low-income countries where the need is most. [5][6][7][8][9][10] Although the causes for their reduced efficacy are unknown, and are an active area of investigation, contributing factors possibly include lower viral titer (transplacentally acquired RV antibodies, components of breast milk and stomach acid) and impaired immune response (malnutrition, interfering microbes, and other coinfections). [11][12][13] From limited available data, lower efficacy in certain subpopulations of the developing world of other live, attenuated oral vaccines has also been observed against enteric pathogens such as poliovirus and Vibrio cholera.…”