Rates of Release of Subcutaneously Injected Antigens in the Rat: Comparison of an Aqueous Preparation with Two Alum‐Precipitated Preparations

Release of antigen E‐ 125 I from the site of subcutaneous injection in male rats was delayed significantly when either of two alum‐precipitated preparations containing 1.0–1.2 mg of Al/ml was administered rather than an aqueous preparation. The rates of 125 I excretion were similarly influenced being statistically slower through the first week after single doses of the alum‐precipitated preparations. The results of these studies strongly support the view that alum‐precipitated vaccines offer more protection from system reactions than aqueous vaccines.