Should the world be caught without an effective vaccine or antiviral treatment for an avian flu pandemic, a last-ditch option may be to inoculate the sick with antibodies from the blood of those who are able to recover from the disease, according to a review of studies published after the 1918 Spanish influenza pandemic.

The H5N1 virus has killed 141 of the 241 people reported to have contracted it. Current manufacturing capacity could vaccinate less than five percent of the worlds population in the event of a pandemic, however, making alternative treatments extremely desirable. One method known to work in other viral diseases such as rabies and measles is to transfer the blood of a recovered patient to a sick one, giving the latter antibodies against the pathogen.

Transfusions were also tried in the 1918 flu pandemic but hadn't been studied extensively, so U.S. military and biotech researchers searched the medical literature published between 1918 and 1925 for reports of the treatment. Those who received blood transfusions were 21 percent more likely to survive a case of influenza-induced pneumonia than those who didn't receive the treatment, they found in a survey of eight studies. Of 336 total people treated, 16 percent died from the pneumonia compared with 37 percent of those in control groups. Of the treated individuals, those who had received a transfusion within the first three days of contracting pneumonia were 41 percent more likely to survive than those treated afterward.

"Our analysis suggests that patients with Spanish influenza pneumonia who received transfusionmay have experienced a clinically important reduction in the risk for death and improvements in clinical signs and symptoms," the researchers report in a paper published online August 29 in the Annals of Internal Medicine. "Our findings are provocative, but our review has important limitations," they point out. The old studies were small and poorly done by current standards.

Nevertheless, "the concept is important and it should be explored further, especially given our lack of proven interventions to prevent or treat illness due to H5N1 influenza," writes John Treanor of the University of Rochester in an accompanying editorial. Serum from recovered patients would be technically simple to prepare and presumably in ample supply, he says, although researchers don't know if those who recover from H5N1 produce copious antibodies. He notes that "controlled clinical studies done now will probably pay a considerable dividend when the pandemic begins."