The effects of different inactivating agents on the potency, toxicity and stability of pertussis vaccine

The effect of heat (56 °C for 10 min), formaldehyde (0·1% at 37 °C for 24h), glutaraldehyde (0·05% at room temperature for 10 min), thimerosal (0·02% at 37 °C for 24 h), acetone-I (three treatments at room temperature) and acetone-II (three treatments at room temperature and fourth treatment at 37 °C), when used as inactivating agents in the preparation of pertussis suspension, was studied with regard to potency, toxicity and stability. Five batches each of Bordetella pertussis strains 134 and 509 were used for the study. The thimerosal inactivated pertussis (TIP) preparation was 1·5−2 times more potent than the heat inactivated pertussis (HIP) preparation. The potency values of the formaldehyde inactivated pertussis (FIP) and glutaraldehyde inactivated pertussis (GIP) preparations were similar to those of the HIP preparation, while the potencies of the acetone-I treated pertussis (A(I)TP) and acetone-II treated pertussis (A(II)TP) preparations were about half those of the HIP preparation. The FIP preparation was the least toxic showing maximum weight gain in the mouse weight-gain test (MGWT), while the TIP preparation did not pass the MWGT. The weight gains shown the GIP, A(I)TP and A(II)TP preparations were greater than those shown by the HIP preparation. The potency of pertussis component in the adsorbed diphtheria-pertussis-tetanus (DPT) vaccine was stable at 4–8 °C and 25 °C for three months for all types of pertussis vaccine. There was about 54–65% loss in the potency of the samples after three months at 35 °C. The inactivating agents used in the manufacture of pertussis preparations had no effect on the stability of the vaccine.