European medical regulators were urgently seeking information Monday from British drugmaker GlaxoSmithKline after finding traces of a virus that normally infects swine in a childrens' vaccine.
DNA originating from the virus -- which is not known to cause disease in either animals or humans -- was found in the Rotarix oral vaccination used to protect against diarrhoea and vomiting, said the European Medicines Agency.
"The findings do not present a public health threat," said the agency in a statement, adding it had decided not to take any action at this stage.
"It is nonetheless clear that viral DNA should not be present in the vaccine and that its source is unclear," it said.
The watchdog has "therefore requested the manufacturer to provide further information as a matter of urgency," said the London-based agency.
Officials from the agency would be joined by counterparts from the World Health Organisation and regulators from Canada and the US to discuss the matter in the coming days, before a decision was taken on what steps to take.
Rotarix is given by mouth to children of six weeks and older to treat the viral infection rotavirus, which causes diarrhoea and vomiting.
It was approved in the European Union in 2006, although the drug is not normally part of EU member states childhood vaccination programmes, said the medical watchdog.