Vaccine Impact Data Should Support Country Decision Making

By December 2016, 81 of the 194 World Health Organization (WHO) member states (42%) had introduced rotavirus vaccine into their National Immunization Program (NIP); and several others had introduced it at the subnational level. The promising early introduction of rotavirus vaccines in 8 countries in 2006, when the vaccines were first licensed in Europe (Rotarix, GSK, Belgium) and the United States (RotaTeq, Merck), included both Gavi (a global vaccine initiative)– eligible and high-income countries. Prequalification of the 2 vaccines in 2008 was accompanied by a WHO policy recommendation in 2009 that all countries should include rotavirus vaccines in their NIPs, and particularly those with high burden of diarrheal illness [1], thus opening the door to rapid global scale-up. Encouragingly, and despite the modest efficacy observed in low-income countries (LICs) and lowerto middle-income countries (LMICs) in Africa and Asia [2–4], there was a surge of national introductions, mostly with Gavi funding support between 2012 and 2014. However, introductions have slowed down in recent years despite Gavi funding, and never started in earnest in Asia, a region with large-birth-cohort countries carrying substantial disease. The review by Burnett and colleagues in this issue of The Journal of Infectious Diseases, demonstrating the global impact of rotavirus vaccines on rates of acute gastroenteritis (AGE) mortality and hospitalization in children <5 years of age, emphasizes that the decision to introduce rotavirus vaccines was correct. The impact of these vaccines on rotavirus-related hospitalizations and the proportion of rotavirus-associated diarrhea admissions were evaluated before and after introduction of the vaccines. Data were available from 27 countries that have introduced rotavirus vaccine into their NIPs, covering the 10-year period from licensure (2006) to December 2016. This review complements and augments data from meta-analyses of postintroduction vaccine effectiveness studies conducted previously [5, 6]. Mortality from AGE in children <5 years of age in countries in the high (n = 3) and medium (n = 11) mortality strata fell 36% and 50%, respectively, and 42% overall (range, 3%–64%). In infants, the overall reduction was 31%. Although these ecological data cannot prove causality, these reductions in AGE mortality declines have been coincident with rotavirus vaccine introductions in a range of countries. The fact that some highand medium-mortality countries have yet to introduce vaccine is a cause for concern. National immunization technical advisory groups (NITAGs) and decision makers in Gavi-eligible nonadopter countries should carefully review their decisions not to introduce these life-saving vaccines, in the face of these data. Introduction decisions are understandably harder for the non-Gavi-eligible LMICs where AGE mortality is lower and vaccine price may be anticipated to be high and less affordable. Decisions to introduce a new vaccine into NIPs are influenced by many factors including local disease burden, vaccine efficacy and safety, and cost-effectiveness of the vaccines. Rotavirus disease burden has been recognized for decades, and regional surveillance networks have informed countries about the ubiquitous nature and high mortality in infants and young children <5 years of age associated with the disease [7]. High-income and upperto middle-income countries make decisions influenced by cost-effectiveness analyses based on strong efficacy against rotavirus hospitalizations. For LMICs and LICs in Africa and Asia, efficacy data were modest (45%–65%) [1–4]. Despite this, increasing national introductions in sub-Saharan Africa have occurred since the first Gavi-eligible country introductions in 2012 [8]. By December 2016, 28 African countries have implemented rotavirus vaccines. However, in this same period, only 2 subnational introductions occurred in Asia (ie, Thailand with a pilot program and the Philippines). E D I T O R I A L C O M M E N T A R Y