GlaxoSmithKline’s live oral vaccine to protect children against diarrhoea cased by rotavirus, the most common diarrhoeal pathogen in children worldwide, has proved safe and effective against an emerging and virulent strain of the virus called G9 in a new study.

GSK’s vaccine, called Rotarix, was first launched in Mexico earlier this year [[10/01/05f]], bringing vaccination for the disease back for the first time since 1999 when Wyeth (they called Wyeth-Ayerst) withdrew its briefly launched RotaShield product after it was linked to several cases of intestinal twisting (intussusception), some of which proved fatal.

GSK’s latest study, conducted in around 60,000 under-twos around the world, provides an important validation of the product’s safety just as it is about to roll out around the world. The analysis looked for, but did not find, any evidence of an increased attributable risk for intussusception in the critical 30-day period after vaccination.

Efficacy data from the trial also revealed that Rotarix cut the risk of rotaviral gastroenteritis and hospitalisations for rotaviral diarrhoea by 85%, with efficacy against the common G1 strain, which accounts for around 50% of all cases worldwide, as well as the rapidly-emerging G9 strain which was first discovered in the mid-1990s and has reached levels of around 20% in some countries. This cross-protection is a crucial finding for GSK, as Rotarix contains only antigens from the G1 strain. A rival live oral vaccine from Merck & Co, called Rotateq and due to reach the market later this year, has antigens from five strains. Rotateq has been submitted for approval in its first markets [[23/03/05d]].

GSK is taking the unusual step of introducing Rotarix in the markets where the need is greatest, in order to make it available to those who need it more quickly, and Merck has said it is also planning a similar strategy. The majority of the estimated 440,000 annual deaths from the infection occur in sub-Saharan Africa and South America.

According to the World Health Organisation, rotavirus estimated to account for between 20% and 70% of hospitalized cases of diarrhoea and 20% of all diarrhoeal deaths in children less than five years of age worldwide.