Rotavirus infections, vaccines and virus variability.

Among all enteric pathogens, rotavirus is the leading cause of severe acute gastroenteritis in infants and young children in Spain and worldwide.1,2 Rotavirus affects 95% of children by the age of 5 years and causes an estimated 2 million hospitalizations and 453,000 infant deaths, most of them in low-income countries.3 Mortality as a result of rotavirus infections is very low in highincome countries. Rotavirus gastroenteritis, however, creates a substantial economic burden on the healthcare systems in these countries.4 In Spain, before the introduction of rotavirus vaccines, it was estimated that 181,626 episodes of acute gastroenteritis occurred each year among children under 5. This translated into 14,342 hospitalizations, 41,701 emergency department visits and 48,320 primary care visits with important implications for the families and the society as a whole.5 In 2009 the World Health Organization (WHO) recommended the inclusion of either of the two licensed rotavirus vaccines into the national immunization programs of all countries.6,7 The Advisory Committee on Vaccines of the Spanish Association of Pediatrics (CAV-AEP) has also recommended the vaccination for rotavirus in all infants because of the morbidity and elevated healthcare burden of the virus.8 Rotavirus vaccines were licensed in Spain between the end of 2006 and early 2007. Currently the only rotavirus vaccine available, although not subsidized, is RotaTeq (Sanofi Pasteur MSD), a pentavalent vaccine consisting of bovine-human reassortant strains expressing different viral capsid protein combinations. Other countries like Belgium, Luxembourg, Austria, Finland, and more recently the UK, have implemented universal mass vaccination programs for rotavirus using a live attenuated human-derived monovalent vaccine (RotarixTM, Glaxo Smith Kline)9 and/or Rotateq. The protective efficacy of these vaccines was evaluated and established by several randomized double-blind, placebo-controlled trials, demonstrating a protection rate against severe rotavirus gastroenteritis of 85% (95% CI: 72,92) for RotarixTM10 and 98% (95% CI: 88,100) for RotaTeq®.11