The Safety of Polio Vaccine

New Zealand Listener, Volume 35, Issue 889, 17 August 1956, Page 27

The Safety of Polio Vaccine

This is the text of a talk on health, broadcast recently from ZB, YA and YZ stations of the NZBS, by DR. |

H. B.

TURBOTT

Deputy-Director- |

General of Health

WANT to help you, a little more, if I can, with this problem of vaccination against poliomyelitis. I know you have 4 feeling of uricertainty about it, and why not? You were just as doubtful about diphtheria immunisation, thirty yeafs ago. In fact, then, only about one parent in three would consent to protection against diphtheria! ‘The history of the Salk vaccine is brief. In 1954 Salk prepared a vaccine from strains of the three known types of polio virus, and inactivated the virus with formalin. Hig tests that he had killed any live virus in the vaccine proved effective enough, for 422,000 chilcren received one or more injections of the vaccine without ill effect. In 1955 the results of this field trial were announced. As compared with the control group of 201,000 children the vaccine gave protection against paralytic poliomyelitis to the tune of 60-70 per cent effective against type I virus, and 90 per cent or more effective against types II and II. Immediately there was a U.S.A. rush to be on the bandwaggon of polio vaccination, One manufacturer failed in his safety testing, and a series of poliomyelitis cases followed the use of the manufacturer’s vactiné. The United States Department of Health traced the breakdown, and prescribed more _ stringent testing for safety by all manufacturers? Between May and mid-November in the Same year, 1955, 21 million doses of polio vaccine were released for use in the United States. At least ten million children received the vaccine in these months, with not an iota of trouble. In this large group there has been protection against paralytic polio. The unvaccinated children have had from two to more than five times more paralytic polio. In Canada more than one million children were vaccinated against polio in 1955 with Salk vaccine without mishap. Preliminary results from four provinces in October, 1955, indicated five times more paralytic polig among the unvaccinated. Wherever the vaccine has been used there have been no untoward reactions after use. We will be using British-made vaccine and "in Britain there has been the same experience as in other countries. I am assufed by the British Ministry of Health that any reactions have been of a local and trivial nature, and that the vaccine has not proved upsetting in use. The safety of the British vaccine to be used in New Zealand is as assured as is humanly possible. I personally

have been over the laboratory where the | vaccine for New Zealand was made. The manufacturers have spared no expense in making this separate laboratory for the manufacture of Salk vaccine. The doctor. in charge was one of the original workers on the Salk vaccine in the Connaught Laboratories of Toronto, Canada. He is not using the Mahoney strain of type I virus that caused the trouble in U.S.A., but a modified Brunhilde’ strain, type I virus, that has less virulence but equivalent immunising power. The three virusés, types I to III, are grown separately, then inactivated with formalin and safety tested separately by making tissue cultures, and examining for live virus, and finally trying them out on live monkeys for ill effects. To make _ sure, the poor monkeys are killed after 28 days, and histological sections of the central nervous system examined microscopically for possible damage. Finally the three strains are bulked, and tissue culture and monkey tests repeated. Safety tests are now made on monkeys made more susceptible to the presence of live virus by being treated with cortisone. Now the vaccine is released to the Medical Research Council and to the National Laboratory Service, of England, where parallel tests for safety are gone through all over again. This multiple testing wastes a lot of vaccine, and the U.S.A. does nothing like such stringent testing, but you can rest assured that adequate safety testing is being done with the British vaccine, I followed the pfocess of making this vaccine through all stages, gowned and masked as though for an operating theatre visit. A high degree of sterility was maintained and, of cotirse, tested continuously. There would not be many operating theatres that could outdo this laboratory in all the measures taken to assure sterility, and I left with the impression that the manufacturer was determined that, within the limits of human possibilities, no child would suffer mishap from being vaccinated with British-made vaccine, Well, that is about all I can tell you. The vaccine will be as safe as man can make it. It will give protection against paralytic poliomyelitis. It is over to you.