Clinical and immunologic evaluation of a purified fraction of ragweed pollen (delta) *1A double-blind study

The delta fraction appeared to be as effective clinically as whole ragweed extract in the relief of symptoms of ragweed pollinosis. The immunologic response, as measured by the hemagglutinating and reagin antibody titers, is essentially the same following treatment with either delta or whole ragweed extract. This fraction can be readily reproduced. Its allergenic activity may be measured in terms of dry weight. This is a definite step toward the standardization of ragweed antigens.