A new rabies vaccine for use in human beings has been developed by the University of Toronto's Connaught Medical Research Laboratories, which says it could be safer than those in use.
It is the first time researchers have succeeded in culturing the vaccine in animal tissue other than brain tissue. The new vaccine is the culmination of years of work by a team led by Dr. Paul Fenje.
Pilot clinical studies have begun in human volunteers, but Dr. J. .K W. Ferguson, Connaught director, said it may be a long time before the vaccine can be released for wide use.
"The problems of demonstrating efficacy of a new vac cine for the prevention of rabies in humans are such that perfectionistic requirements might defer general use for very many years," he states in the annual report of the Laboratories.
Since the days of Pasteur, rabies vaccine has been cultured in animal brains. It is impossible to remove all brain protein and fatty substances from the vaccine, and these often cause swelling and irritation at the site of the injection and occasionally alarming reactions in the central nervous system.
In treating a person who has been bitten, 14 abdominal injections are given on consecutive days. If given as a protection to persons likely to be exposed, such as veterinarians, only four or five injections spaced at intervals may be needed, because there is more time for the body to build up protective antibodies.
A safer vaccine has been made from virus cultured in duck embryos, but it is less effective and is not used to treat an individual already bitten.
The pilot studies will be carried out in veterinarians, who risk exposure, and their anti- body levels will be measured to determine the vaccine's effectiveness.
Dr. Ferguson, in his report, said a safe vaccine would be much more acceptable as a preventive measure for per sons working with animals who may be exposed to danger.
The new human vaccine is also made from killed virus, but a Connaught team led by Dr. Melvin Abelseth has also produced a live virus vaccine for animal use, which has now been licensed for sale.
Dr. Ferguson's report said the Laboratories are also making good progress toward a vaccine against German measles, which can cause abnormalities in an unborn child if caught by the mother early in her pregnancy.
This, too, must be a killed virus vaccine. A live virus I would make an effective vaccine, but it might be transmit ted unwittingly from the per- son vaccinated to a pregnant woman.
Other recent successes at the Laboratories include production of a dried smallpox vaccine, which retains its potency at high temperatures, and a new combined vaccine for the armed services which immunizes against typhoid, paratyphoid, tetanus, diphtheria and poliomyelitis.
The dried smallpox vaccine, licensed last year, was produced in case it might be needed by Canadian forces operating in hot countries. Liquid vaccine quickly loses its potency in tropical heat.
Dr. A. L. Tosoni and coworkers have produced an enzyme derived from a mold called Aspergillus oryzae, which can dissolve blood clots.
Medicine makes wide use of substances which prevent blood coagulation (the first, heparin, was also a Canadian discovery) but so far has had little success with materials to dissolve clots once they have. formed.