A study of the stability of the pertussis component of diphtheria-tetanus-pertussis (DTP) vaccines

Stability of Vaccines

Vaccines are considered the most economical and effective preventive measure against most deadly infectious diseases. Vaccines help protect around three million lives every year, but hundreds of thousands of lives are lost due to the instability of vaccines. This review discusses the various types of instability observed, while manufacturing, storing, and distributing vaccines. It describes the specific stability problems associated with each type of vaccine. This review also discusses the various measures adopted to overcome these instability problems. Vaccines are classified based on their components, and this review discusses how these preventive measures relate to each type of vaccine. This review also includes certain case studies that illustrate various approaches to improve vaccine stability. Last, this review provides insight on prospective methods for developing more stable vaccines.

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

The effect of heat (56 degrees C for 10 min), formaldehyde (0.1% at 37 degrees for 24h), glutaraldehyde (0.05% at room temperature for 10 min), thimerosal (0.02% at 37 degrees C for 24h), acetone-I (three treatments at room temperature) and acetone-II (three treatments at room temperature and fourth treatment at 37 degrees 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 (TIP) 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 degrees C and 25 degrees 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 degrees C. The inactivating agents used in the manufacture of pertussis preparations had no effect on the stability of the vaccine.

Effects of elevated temperatures on the opacity and toxicity of pertussis vaccines manufactured with different inactivating agents

Plain pertussis vaccine manufactured with different inactivating agents was evaluated for its stability at 4-8, 25 and 35 degrees C with regard to the opacity and the toxicity [mouse weight gain test (MWGT) and histamine sensitizing (HS) activity]. Two pools each of heat inactivated pertussis vaccine (HIPV), formaldehyde inactivated pertussis vaccine (FIPV), glutaraldehyde inactivated pertussis vaccine (GIPV), thimerosal inactivated pertussis vaccine (TIPV) and acetone (I) treated pertussis vaccine [A(I)TPV] were taken for the study. The test for determination of opacity and MWGT were performed at monthly intervals for three months and the test for HS activity was performed after three months exposure of the samples at various temperatures. There was almost no loss in the opacity of GIPV and TIPV at all the selected storage temperatures and of HIPV and FIPV at 4-8 degrees C, while A(I)TPV lost about 16% opacity in three months at 4-8 degrees C. At 25 degrees C after three months, the percentage loss in opacity of HIPV averaged about 12, of FIPV 17 and of A(I)TPV 33. At 35 degrees C after three months, the average percentage loss in opacity of HIPV was 16, of FIPV was 25 and of A(I)TPV was 33. Regarding the effect of elevated temperatures on the toxicity of the vaccine, it was observed that the samples held at 35 degrees C for three months were the least toxic followed by those held at 25 and 4-8 degrees C as detected by MWGT and the test for HS activity.