The big news came in three words: “The vaccine works.”
That was how the University of Michigan started off its terse summary of the verdict on the Salk polio vaccine. The reading of the report itself took longer, and the setting in the university’s Rackham auditorium was elaborate. Under the klieg lights set up for TV and newsreel cameras, surrounded by microphones and 150 reporters, sat the unquestioned hero of the occasion: Dr. Jonas Edward Salk, 40, the determined, youthful-looking virologist who for five years had battled in his University of Pittsburgh laboratory to lick polio. Next to him sat the University of Michigan’s Dr. Thomas Francis Jr., 54, one of the U.S.’s most eminent epidemiologists, who had been chosen by the National Foundation for Infantile Paralysis to evaluate last year’s nationwide tests of the Salk vaccine. For an hour and a half, Dr. Francis read his report in an even, matter-of-fact tone. The gist: ¶The vaccine is up to 90% effective. ¶The vaccine causes a minimum of undesirable side effects —all, apparently, minor. ¶ Results were most favorable from the areas where conditions were best for accurate appraisal. Dr. Francis stopped when he finished telling what had been done. Dr. Salk. who rose to a standing ovation from 500 usually undemonstrative scientists, took a peek into the future: the vaccine, he suggested, might be made almost 100% effective. This does not mean that polio will be suddenly abolished. But it could mean that as vaccination becomes universal for children, whole generations will grow up free of the paralysis that has condemned so many to enfeebled limbs or iron lungs. Eventually, polio can become as rare as smallpox—which U.S. doctors now rarely get a chance to identify. The Test. The task of deciding how good the vaccine is, which seems so easy, proved forbiddingly difficult, though Dr. Francis had all the help he needed from Michigan’s School of Public Health, the U.S. Public Health Service and even the Bureau of the Census. The test vaccine was given in 127 areas, deliberately picked because they had had a high polio-attack rate for several years. This was to make sure that there would be enough cases for the epidemiologists and their statistical machines. No fewer than 1,830,000 children were studied in the trials (440,000 were inoculated with the vaccine, 210,000 got a dummy substance, 1,180,000 were merely observed as “controls”). Among these children, there were only 1.013 cases reported as polio (in the U.S. as a whole there were 38,000 cases in 1954). And the disease is so hard to identify that 150 of the reported cases were thrown out, leaving Dr. Francis’ staff only 863 confirmed polio cases. But from a mountain of data about the cases that did not develop as well as about those that did, Dr. Francis’ team gathered these principal facts: The Vaccine Is Safe. “Minor reactions,” meaning a touch of headache or fever, or soreness at the injection site, were just as common among children who got the dummy shots as among those receiving vaccine; possible “major reactions” such as high fever or severe rash were actually more common among those who got the placebo shots. No major reaction could be definitely laid to either sub-stante; the evidence was that all were either coincidental or psychosomatic. Most important, perhaps: no child developed polio as a result of vaccination. It Is Effective. Of those who received vaccine, only 57 developed polio. Of these, only one died: Patricia Redick, 8, of Tulsa. She received her first shot in April, then had her tonsils out, got a second shot in May and died two weeks later. In Patricia’s case, two things were wrong: the vaccinations were too late, because Oklahoma’s early polio season had already begun, and it has long been known that a tonsillectomy is dangerous when polio threatens. Proportionately, there were 2½ times as many polio cases (142) among children who received dummy shots as among those who received real vaccine. Still more encouraging statistically, the unvaccinated had 3½times as many paralytic cases, and there was a kind of protective gradient: the more severe the type of paralysis, the greater the difference in incidence between those who got the vaccine and those who did not. In other words, the vaccine appears most effective against the worst forms of polio. These results were most clear-cut in the eleven states where vaccine was contrasted with placebo; in the 33 states where children received either real vaccine or nothing, the results were similar but a bit blurred. (Probable reason: anxious parents of children who got no shots may have had them inoculated on the side with gamma globulin, which has a short-lived protective effect.) Among the children who were observed for evidence of polio but who got no shots, there were eleven deaths. Among children who got placebo shots, there were four deaths. It Is Potent. This quality was measured by the vaccine’s ability to raise the bloodstream concentration of antibodies that can defeat an invasion by the polio virus. To prove it, 27,000 blood samples from 9,000 children, taken before and at intervals after vaccination, were meticulously studied. (This part of the evaluation program alone involved highly technical work with 2.000,000 test tubes, took five months.) However, no sooner had Dr. Francis finished reporting his results than Dr. Salk rose last week to confirm newer findings at which he had hinted last fall (TIME, Sept. 20). If three shots are given within five weeks, as was done last year, the effectiveness of the vaccine will last for at least a polio season. But if two shots are given within a month, and there is then an interval of at least seven months before a third shot is given, two advantages are gained: 1) the strength of antibodies is raised more quickly and to a much higher level (higher, often, than would follow a natural infection with polio), and 2) the immunity lasts longer because the system’s antibody-manufacturing plant develops an “immunologic memory” or conditioned reflex. It Will Get Better. So far, Dr. Salk does not know whether this degree of immunity will last for a lifetime or only a few years. He can go back only 2½ years in pointing to test subjects who have enjoyed vaccine-conferred immunity. So it may be that all the vaccinated will need booster shots every five or ten years. However, this is more a scientific possibility than a probability. In summary, Dr. Francis suggested that the vaccine had been 80-90% effective in the placebo-control states and 60-70% effective in observed-control states. Most vaccines now in general use against virus diseases are rated 95% effective, but none achieved this in the first year or two of testing.