Government of India set up a plant for producing Freeze-Dried vaccine at BCG Vaccine Laboratory, Madras in 1959. Before releasing the freeze-dried vaccine to the mass campaign it was necessary that it is subjected to various tests. This paper deals with two such trials. The first study planned in this connection was for the assessment of allergising properties of two lots each of four batches of freeze-dried vaccine. The second study was to investigate the stability of two lots of a batch of freeze-dried vaccine in relation to storage at different temperatures for varying periods.

The results indicate that though the liquid vaccine has on the whole produced slightly higher allergy than the freeze-dried vaccine, the level of allergy achieved with the freeze-dried vaccine is quite adequate. Levels of post-vaccination allergy in the lots containing glutamate and tween 80, show that increase in storage temperature has resulted in higher loss of potency of vaccine. No definite trend is indicated regarding the lots containing glutamate alone.

Liquid BCG vaccine produced upto 1955 at the BCG Laboratory, Guindy, Madras induced low and variable levels of post-vaccination allergy. However, subsequent to improvement in production, its potency was adjudged as equivalent to Danish BCG vaccine. Later on, lower levels of post-vaccination allergy in Mass BCG vaccination campaign and in research studies were observed. A study was planned to compare the Madras BCG vaccine with Danish vaccine in terms of the potency of the strains, production efficiency of the laboratory and stability on storage. This was done by comparing the allergising capacity and size of vaccination lesions. On a predetermined date in each of four consecutive months, both laboratories supplied to the Research Team one week of fresh vaccines from their respective BCG strains and also fresh vaccine of strains borrowed from the other laboratory. With these six vaccines every month, in two consecutive weeks randomly, vaccinations were given to 2,978 tuberculin non-reactors. post-vaccination allergy was elicited 10 weeks later when size of BCG lesion was also noted. Viable counts on all vaccines were done by Madras Laboratory.

Though the Indian and Danish BCG vaccines induced similar levels of allergy, on further analysis it was found that Madras BCG strain was inferior to the Danish strain and that Madras Laboratory produced better vaccine than Copenhagen Laboratory. The vaccine produced from Copenhagen strain in Madras Laboratory induced the highest level of allergy. The stability of vaccines produced from Madras strain was found to be unsatisfactory. Results according to vaccination lesion size and their correlation with tuberculin reaction more or less confirmed the above findings. They were however not corroborated in terms of viable counts. Considering that the inferior quality of Madras BCG strain was due to mutation over time, seed lots of suitable BCG strain would ensure uniformly potent vaccine from Madras Laboratory.