The broad and complex problem of polio dominated the first half of the twentieth century. Major research progress was stymied until 1949 when a way was finally found to grow the poliovirus in a test tube, instead of having to rely on monkeys for all research. This Nobel Prize winning advance greatly stimulated polio researchers, including those at Connaught Laboratories.

Dr. Andrew J. Rhodes had led a major polio research program at Connaught since 1947, and by 1951 he was also growing poliovirus in test tubes. Yet not enough virus was bein gproduced to be practical for a vaccine until one of Rhodes'associates, Dr. Arthur E. Franklin, tried a new method that involved the nutrient base known as "Medium 199." This medium was a complex and chemically pure mixture of over 60 ingredients that was the first of its kind. "Medium 199" was developed at Connaught in 1949 by Dr. Joseph F. Morgan, originally for studying cell nutrition in cancer research. Morgan and Franklin were close friends and after discussing the problems Franklin was having with growing the poliovirus, Morgan supplied some "199" to Franklin in the fall of 1951 to see if it could help, and to his surprise "199" worked incredibly well.

Meanwhile, Salk was confident that an inactivated vaccine could prevent polio in humans as it seemed to in monkeys. However, his vaccine was not yet safe for human use, nor could he make enough for the millions of families who were clamoring for protection from the dreaded disease. It was in solving these two major problems that Connaught made its crucial contributions. Medium 199 provided a chemically pure basis for a safe vaccine, while in 1953, Connaught researcher Dr. Leone Farrell came up with the "Toronto technique" to produce bulk quantities of the poliovirus by using large bottles that were gently rocked in a series of specially designed rocking machines.

In early 1952, when the NFIP and Salk first heard about the value of "199," this gave Salk confidence to prepare a vaccine that would now be safe to try on children. In January 1953, the residents of a disabled children's residence near Pittsburgh were the first to get Salk's vaccine. In the meantime, the AmericanM arch of Dimes poured money into Connaught to expand their methods of growing the virus for a large field trial. Connaught had already established a prominent international reputation for making vaccines and other public health products, and since it was a non-commercial manufacturer, a more open and cooperative relationship with Salk and the NFIP was possible.

By the summer of 1953, Connaught was asked by the NFIP to provide all the poliovirus fluids required for a national field trial set to begin in the spring of 1954. Through the fall and winter of 1953-54, large bottles full of poliovirus were sent in station wagons from Toronto and over the border to drug companies in Detroit and Indianapolis, where the virus was inactivated and processed into a finished vaccine. Monkey kidneys were necessary for growing the virus and during this time at least 165 monkeys were needed per week to produce the 3,000 litres of virus fluids needed for the trial. To Salk the efforts of Connaught in this project were "Herculean" in magnitude, and without their collaboration there could never have been a trial since no American laboratory had the experience or facilities to undertake such a financially risky project.

After a number of delays, the NFIP's mammoth vaccine trial began on April 26, 1954 and involved the elaborate tracking of some 1,800,000 children who were either given the vaccine, the harmless "199" as a placebo, or were simply observed to see if they contracted polio or not. In appreciation of Connaught's crucial role, the NFIP offered the Canadian government some surplus vaccine in May 1954 and were invited to take part in the trial. But the lateness of the offer was not overly appreciated by Ottawa, or most of the provinces. However, the seriousness of the unprecedented 1953 polio epidemic in some provinces, especially in the west, pressured Manitoba and Alberta, and the City of Halifax to accept the offer. For Connaught and the federal government, their sights were set on an all-Canadian field trial of Salk's vaccine which would begin in the spring of 1955, no matter what the final results of the American trial were.

On April 12, 1955, the announcement of the highly anticipated field trial results turned into a major media event and a rare example of good news. After being immediately licensed, American vaccine producers rush released their vaccine to the U.S. public, but with little government control. The Canadian trial was just starting by then, but unlike to the south, the federal and provincial governments shared the full cost of the vaccine and distributed it free to children in grades 1 to 3, who were most susceptible to polio.

By the end of April, the public euphoria over the Salk vaccine was shattered when a total of 79 children given vaccine from Cutter Laboratories in California contracted polio. This forced Cutter's vaccine off the market, and by May 8, the cancellation of the entire U.S. vaccine program by the U.S.Surgeon General.

In Canada, the Minister of National Health and Welfare, Paul Martin, faced a difficult decision: what should Canada do? The Prime Minister didn't want the Canadian trial to continue, but based on the long experience of Connaught with polio research and the development of the vaccine, Martin maintained his confidence. The vaccine had not yet caused any problems in Canada and so the immunization program continued, and never did cause any Canadian troubles.

The Canadian confidence in the vaccine meant a lot to Jonas Salk and bolstered his bruised confidence in the vaccine. The success story of the Canadian polio vaccine program attracted alot of American press and political attention, sharply highlighting the differing levels of government interest in planning, testing, distributing and paying for the vaccine between the two countries. The prominence of the Canadian and Connaught vaccine program also played a major role in ensuring its future international use in the control of polio.

The 1954-55 Salk vaccine field trial was unprecedented in medical history and not only demonstrated the value of the vaccine against paralytic polio, but also involved a strong Canadian connection that was crucial to the future control of this dreaded disease around the world.