a1 Vaccine Lymph Unit, Lister Institute of Preventive Medicine, Elstree, Herts
1. Requirements for a heat-stable smallpox vaccine are suggested.
2. Sheep lymph dried from the frozen state retains its potency at 22 and 37°C. better than aqueous, glycerinated or lanolinated suspensions of lymph. Dried crude lymph is not, however, sufficiently stable for use in tropical areas; it is also liable to vary in stability from batch to batch. No better results were obtained by prolonging secondary desiccation.
3. Phenol in low concentration is deleterious to vaccinia virus stored in the dried or liquid state at 22 and 37° C.
4. Dried vaccinia virus stored under nitrogen loses potency more rapidly than when sealed in vacuo, even when precautions are taken to rid the nitrogen of traces of oxygen and moisture.
5. A number of suspending media were examined for their preservative influence on purified vaccinia virus. None was effective in the liquid state, but all protected the virus against the lethal influence of freeze-drying. In the dried state, these media varied in their ability to protect the virus during storage at 22 or 37° C. The best results at both temperatures were obtained with virus freeze-dried in 5% peptone. This medium also protects the virus well at 45° C. Different types of peptone were equally effective.
6. Virus dried in 5% peptone still gave a full quota of successful primary vaccinations of children after storage for 12 months at 22° C., or for 4 months at 37° C.
7. Using partially purified sheep virus dried in 5% peptone, a vaccine can be produced which shows a high degree of resistance to heat, is relatively free from bacterial contamination, and is easy to reconstitute after prolonged storage. These results are highly reproducible.
(Received September 16 1954)
* This paper is based on a thesis accepted in December 1952 for the M.D. Degree of the University of London.