Merck & Co was given the go-head on Friday to launch its Rotateq vaccine against rotavirus, a common cause of diarrhoea in children, in the USA.

Once launched, Rotateq will be the first vaccine available to combat rotavirus since 1999, when Wyeth’s RotaShield was removed from the market after being linked to a severe twisting of the bowel known as intussusception.

This withdrawal left a vacuum in the marketplace that could help Rotateq achieve sales in excess of $500 million a year, according to analysts. Rotavirus causes around 55,000 young children to be hospitalised each year in the USA, and while rarely fatal in developed countries is a major killer of children in the developing world.

Merck says that there is no evidence that Rotateq causes intussusception, citing clinical data on almost 72,000 children who received the vaccine in a clinical trial known as REST.

But the company has agreed to carry out close monitoring of those who receive it, in collaboration with the US Food and Drug Administration (FDA), to make sure any cases are picked up swiftly. Merck has committed to carrying out a 44,000-children study to provide further data on Rotateq’s safety, while the FDA and Centers for Disease Control (CDC) will monitor the product via their existing surveillance system for vaccine recipients, which assesses around 80,000 infants a year.

Merck has been going head-to-head with UK-headquartered rival GlaxoSmithKline in a race to bring rotavirus vaccination back to the marketplace, although the US drugmaker had an uncontested run in the USA as GSK has yet to file its candidate, Rotarix, with the FDA.

Rotarix was the first of the two to be launched, debuting in Latin America in keeping with GSK’s strategy of concentrating its initial efforts on regions where there is the greatest need. It is also approved in some Asian countries, and is due to be approved soon in Europe.

Rotateq is being developed in Europe by Sanofi Pasteur MSD, and is under review having been submitted for approval there in April 2005. Merck said in January that it will start testing in developing countries later this year.

- Meanwhile, Merck has also said that it application to market its much-anticipated cervical cancer vaccine Gardasil is ‘on track and pending acceptance’.