The death rate among swine flu patients was more than halved after they received transfusions of blood plasma from recovered patients, a study in China has shown.
The "convalescent plasma" method sees severely ill patients given plasma from patients who have recovered from the same strain of flu.
The Chinese study involved 93 seriously ill swine flu patients in Hong Kong between September 2009 and June 2010 - 20 received 500 millilitre plasma transfusions from recovered patients and the other 73 acted as comparison "controls".
Although 20% of the treated group died, this was well below the 55% death rate amongst the control group.
Those given the transfusion also saw a faster rate of decrease in the number of active viruses in the blood, and none of the patients suffered any adverse reactions.
The research, published in the Clinical Infectious Diseases journal, says: "This study has demonstrated that convalescent plasma treatment may have a place in the treatment of patients with severe H1N1 2009 infection."