The Salk vaccine of 1954 was safe, as was proved by more than 400,000 inoculations with only 71 subsequent cases of paralytic polio (none of them attributable to the vaccine). But the Salk vaccine of 1955 is not the same as that of 1954. A big difference is in the testing procedures.
How the Tests Work. On the face of it, nothing could be more thorough than the inactivation and testing procedures worked out by Dr. Jonas E. Salk and adopted as standard by the Public Health Service. To "kill" or (more precisely) inactivate the virus, a formaldehyde solution is added to...
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