GlaxoSmithKline has received a boost from promising data from a late-stage trial of its new vaccine Rotarix which again demonstrated that the jab is effective at protecting against rotavirus, the primary cause of severe acute gastroenteritis in young children.

Phase IIIb data from a European trial involving six countries, published in The Lancet, revealed that Rotarix provided high levels of protection against the five most common rotavirus types – G1, G2, G3, G4 and G9 – which are responsible for 98% of rotavirus gastroenteritis cases. Researchers at the University of Tampere in Finland noted that during the first efficacy follow-up period, 24 out of 2,572 infants given Rotarix had rotavirus gastroenteritis episodes of any severity compared to 94 out of 1,302 given placebo, resulting in a vaccine efficacy of 87.1%.

Efficacy after two doses over two consecutive rotavirus seasons was 90.4% against severe rotavirus gastroenteritis and 83.8% for rotavirus-related medical attention. The authors of the study concluded that “if integrated into routine infant immunisation schedules, vaccination with Rotarix could result in significant reduction not only of rotavirus disease burden but also of severe paediatric gastroenteritis during the first two years of life".

Every year rotavirus diarrhoea causes over half a million deaths, more than 25 million outpatient visits and more than 2 million hospital admissions in children aged under five. Although most rotavirus-related deaths occur in low-income countries, 220,000 children a year in industrialised countries are admitted to hospital, noted Australian paediatric experts Keith Grimwood and Julie Bines in a Lancet comment piece.

They noted that while experience from this trial and studies in Latin America show that the GSK jab might do well in low-income countries in Africa and Asia, where rotaviruses circulate all year and where 81% of hospital admissions due to rotavirus and 80% of global rotavirus-related deaths occur in infancy, “the capacity for Rotarix to offer cross-protection will be tested, because in Africa and Asia rotaviruses show substantial strain diversity”. Consequently, “no global recommendations for rotavirus vaccines can be made” until trials of Rotarix and Merck & Co’s rival product RotaTeq in Africa and Asia are completed.

The European market is a small one but the USA is significant and GSK filed Rotarix there in August. However it has a fair bit of ground to make up on Merck's Rotateq which had third-quarter sales of $375 million, nearly all of which came in the USA. Rotarix is licensed in around 100 countries and was approved in the European Union in February 2006.