Comparisons of alum-precipitated and unprecipitated aqueous ragweed pollen extracts in the treatment of hay fever

In 1969 and 1970, groups of patients with ragweed hay fever never before treated were started on preseasonal courses of immunization with an alum precipitate of aqueous ragweed extract. A comparison between these two groups of patients and a similar group of patients treated with unprecipitated aqueous extract in 1968 shows that treatment with alum precipitate was safely initiated with fewer injections even though a higher dose was administered. The larger cumulative dose appeared to give better IgG antibody responses and greater relief of symptoms. A repeat preseasonal course the next year again required fewer injections of the alum-precipitated extract than a repeat course of aqueous extract.