Effect of storage at 37 degrees C on immunizing power of dried BCG vaccine.

Experiments were carried out to determine the effect of storage at 37 degrees C on the immunizing power of dried BCG vaccine. Vaccines were prepared with sodium glutamate and with sucrose, and were preserved for 6 months at 5 degrees C and at 37 degrees C. The preserved vaccines were then injected into four groups of 12 tuberculin-negative guinea-pigs; a fifth group of 12 non-vaccinated animals acted as controls. Six weeks after inoculation, all surviving animals were given a challenge dose of virulent human tubercle bacilli. After a further six weeks the guinea-pigs were killed, and an examination was made of the macroscopic and histological changes produced in the lymph-nodes and viscera.No significant difference in the tuberculous changes induced by the challenge infection was observed among three of the groups of vaccinated animals-namely, the two inoculated with the sodium glutamate vaccines and the one inoculated with the sucrose vaccine preserved at 5 degrees C. The fourth vaccinated group showed greater changes than the other three, indicating that the immunizing power of the sucrose vaccine had decreased markedly during storage for 6 months at 37 degrees C. The non-vaccinated control group, however, showed the most conspicuous changes of all the five groups.