From the *National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA; and †PATH, Seattle, WA.
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Worldwide, diarrhea is the second most common cause of fatal childhood disease, estimated to cause approximately 1.34 million deaths among children aged <5 years.1 Rotavirus is the leading cause of severe diarrhea in young children and is responsible for approximately one-third of all diarrheal deaths.2 Two effective rotavirus vaccines, a single-strain attenuated human rotavirus vaccine (Rotarix, GlaxoSmithKline Biologicals) and a multistrain bovine-human reassortant vaccine (RotaTeq, Merck and Company), are now available and recommended for routine immunization of all infants by the World Health Organization (WHO).3 Efficacy of these vaccines has ranged from 80% to 98% in industrialized countries,4–7 including Latin America, and 39% to 77% in developing countries, such as Africa and Asia.8–10 On the basis of efficacy data from Europe and America, the WHO initially approved use of the vaccines in these regions in 2006 and within 2 years several countries added rotavirus vaccination into their routine immunization programs. Subsequently, after proof of efficacy in Asia and Africa, the WHO recommendation was expanded to all infants worldwide in 2009.3As rotavirus vaccines are implemented within national childhood immunization programs, evaluation of their effect is important for several reasons.11,12 First, routine immunization occurs in real-world conditions different from ideal clinical trial settings. Thus, monitoring postlicensure impact on rotavirus disease is crucial for ensuring that appropriate gains in terms of expected vaccination benefits are attained. Second, changes in the epidemiology of rotavirus disease might occur in the postlicensure era, such as shifts in average age at infection, seasonality of disease, and serotype distribution after vaccination or appearance of unusual genetic variants. Third, ensuring that protection is conferred through the first and second years of life when most severe disease and mortality from rotavirus occur will be crucial for the success of a rotavirus vaccination program. Finally, assessing whether vaccination has an affect on rotavirus transmission in the community, thus providing benefits to unvaccinated groups, is important. Monitoring impact with focus on these public health considerations will not only allow assessment of the effectiveness of rotavirus vaccines in routine use, but also generate the necessary evidence to inform public health policy decision-making and continued investment in rotavirus vaccines.The articles in this supplement elegantly describe the experience of early-introducer countries in Europe, America, and Australia, and address these relevant postlicensure topics (Table 1). The effect of rotavirus vaccines on burden of severe childhood diarrhea in these early introducer countries has been rapid, easily measured, and substantial, demonstrating the health value of rotavirus vaccination. Two of the most interesting and unanticipated findings in the early rotavirus vaccine era have included indirect protection and changes in rotavirus seasonality.13,14 The lessons learned to-date will be valuable for other countries, considering the introduction of rotavirus vaccines into their childhood immunization programs.HEALTH IMPACT OF ROTAVIRUS VACCINATIONSome of the questions related to vaccine performance, duration of protection, and indirect benefits can be answered by clinical trials, and targeted studies designed to specifically address a priori study questions. However, a more cost-efficient and practical assessment that comprehensively addresses the question of whether the country investments are providing intended results could include analysis of pre-existing databases to assess issues suitable for the needs of decision-makers and parents.12 The first set of articles in the supplement use existing databases to evaluate the health impact of rotavirus vaccination in a variety of low-middle, middle, and high income countries.