Doubts have arisen over the effectiveness of swine flu drug Tamiflu after research showed it can cut the length of time people experience symptoms by around a day - but there is little evidence that it has any effect on preventing complications like pneumonia.
The findings, published in the British Medical Journal, come in the same week the government faces disarray over its plans to vaccinate more than three million under-fives against the bug.
GPs and ministers failed to reach an agreement on the swine flu vaccination programme for younger children, with local NHS managers to ask health visitors and district nurses to step in.
The BMJ research has questioned the validity of research from Roche, the pharmaceutical giant that makes Tamiflu.
More than a million courses of antivirals including Tamiflu have been given out to people across Britain since the start of the swine flu pandemic.
A review of 20 existing studies was carried out by a team led by experts from the Cochrane Collaboration, which last reviewed the evidence in 2005.
Their updated study found Tamiflu “did not reduce influenza-related lower respiratory tract complications”.
The drug was found to induce nausea while evidence of adverse reactions to the drug were “possibly under-reported,” they said.
Dr Fiona Godlee, editor in chief of the BMJ, said: “Governments around the world have spent billions of pounds on a drug that the scientific community now finds itself unable to judge.”