Influence of Preservatives, of Heat, and of Irradiation on Mouse Protective Activity and Detoxification of Pertussis Vaccine

Summary

Portions of pertussis vaccines, prepared from cultures of one strain of Haemophilus pertussis grown on Bordet-Gengou medium for 48 hours were treated with 3 preservatives, heat at 34 and 56 C, and ultraviolet irradiation. After treatment all were held at 6 C. During the first year after preparation, frequent protective activity tests were made by the intracerebral method and again at the end of 3 years. Toxicity was determined at intervals, by intradermal reaction in rabbits and by death of or weight loss in mice, until each fraction was relatively atoxic. The best detoxification and stabilization of potency was obtained by heating the vaccine at 56 C for 30 min. or 1 day at 34 C and preserving it with merthiolate. Merthiolate alone had the least effect on both toxicity and potency. Phenol caused the most rapid loss in both properties. Formalin also reduced toxicity, caused some loss in potency and in addition clumping of the bacteria. Heating of the vaccines containing the 3 preservatives at 34 C for longer than 1 day and up to 7 days increased the rate of loss of potency, as the vaccines aged, in direct relation to the time of heat exposure. The amount of irradiation required to destroy toxicity markedly diminished the potency of the vaccine.