Should rotavirus vaccines be included in the national immunization program of a small developed country?

Rotaviruses are the most common cause of severe gastroenteritis in infants and young children worldwide. Virtually all children are infected by the age of 5 years. Annually, rotaviruses cause 114 million episodes of diarrhea, 25 million clinic visits, 2.4 million hospital admissions and more than 500,000 deaths in children up to 5 years of age [1,2]. Although most deaths are in developing countries, every year more than 220,000 children living in industrialized nations are hospitalized owing to rotavirus gastroenteritis [1,3]. Rotavirus accounts for almost half of gastroenteritis admissions in New Zealand [4]. In a recent study, we predicted 1500 hospital admissions, over 3000 emergency department presentations (without subsequent admission) and approximately 10,000 general practitioner consultations in 2009 for children under 5 years of age with rotavirus gastroenteritis [5]. We also estimated that by the age of 5 years, one in five children will have sought medical advice for rotavirus gastroenteritis and one in 43 will have been hospitalized. Given the low annual mortality rate in this age group (<1 or 2 per 100,000 population), attributable to easy access to high-quality healthcare, one of the challenges facing the introduction of rotavirus vaccines is to determine whether they are cost effective compared with the management of acutely ill cases. Two highly eff icacious oral, liveattenuated rotavirus vaccines are licensed in more than 100 countries to date and are incorporated into at least 16 national immunization schedules. One vaccine (RIX4414, human rotavirus; Rotarix, GlaxoSmithKline, Belgium) is derived from a single human rotavirus strain (G1P [6]) and is administered in a two-dose series. The other (pentavalent rotavirus vaccine; RotaTeq, Merck & Co., USA) contains five bovine–human reassortant strains (G1–G4,P [6]) and requires three doses [7]. In highand middle-income countries, both vaccines provide 80–100% protection against severe rotavirus gastroenteritis and 70–80% protection against rotavirus diarrhea of any severity [8]. Post-licensure monitoring of RotaTeq in the USA and Australia report that, shortly after its introduction, there was a reduction in rotavirus disease by twothirds [6,9]. This decline was greater than anticipated for the level of vaccine coverage achieved in the USA, while reduced rotavirus disease in older age groups was also observed in Australia, where initial coverage rates were much higher. Together, these observations suggest additional indirect benefits (herd protection) for unvaccinated individuals from decreased rotavirus transmission. A recent case–control study from Nicaragua found that RotaTeq reduced severe rotavirus diarrhea by 52–63% [10]. In South Africa and Malawi, a Phase III trial demonstrated that for every 100 infants immunized with Rotarix, three episodes of severe rotavirus gastroenteritis were prevented [11]. These developments recently prompted the WHO to make a global recommendation for rotavirus vaccines to be included in national immunization programs [12]. Richard Milne