329 



Dr. Salk gave a detailed presentation of the theory and history of 

 the production of his vaccine. Upon questioning he assured the panel 

 and the committee that the advantages of using the controversial 

 Mahoney strain, the most virulent paral;vi:ic strain then isolated, over- 

 weighed the disadvantages because the inoculated individual would 

 then have immunities against this extremely severe form of polio. He 

 added, however, that work was continuing on development of a less 

 \drulent vaccine. He also assured the panel that the manufacturing 

 process was designed to insure that the viruses do not become reacti- 

 vated after inoculation; the inoculated child could not transmit the 

 disease unless there was sometliing wrong with the vaccine.'^ 



Much of the panel presentation concentrated on the manufacturing 

 process and safety precautions used to insure that all the virulent virus 

 had been inactivated. Dr. Stanley described the inactivation process — 

 the chemical reaction between formalin and the virus proteins. But as- 

 surances of safety could not be given by chemists, he concluded, until 

 they learned about the inactivation process. At the same time, they 

 were working on the use of ultraviolet rays as a complementary 

 inactivating agent. '^^ 



Dr. James Shannon, assistant director, National Institutes of Health, 

 gave an overview of the manufacturing methods and of safety precau- 

 tions. He stated that not only the Cutter laboratories, but all of the 

 producers had difficulty with clumps of live virus remaining in the 

 vaccine. He presented an overview of revised PHS safety regulations : 

 revision in the time schedule for killing and checking the virulence of 

 the virus, improvement of culture tests to discriminate between positive 

 and negative virus, and the addition of more safety tests, especially 

 after the lot had been declared safe.^^ There followed a lively debate 

 between scientists asked by Eepresentative Wolverton as to whether to 

 recommend complete suspension or continuation of use of the Salk 

 vaccine, and whether to recommend substitution of a less virulent 

 strain for the Mahoney virus in that vaccine. Dr. Sabin, who was 

 then working on the development of an oral attenuated polio virus, 

 was most outspoken about halting the Salk program. He stated that 

 while the new safety tests were an improvement, the vaccine was still 

 not safe because of the use of the virulent Mahoney strain. He added : 



I am fully aware of the excellent humanitarian motives of those people who 

 do not want to wait until the best possible vaccine has been developed to provide 

 this protection to those who may get it now. Their motives are of the best and 

 highest * * * But in attempting to do it at a time when we cannot be absolutely 

 certain of avoiding another incident such as has occurred, we may eventually do 

 more harm than good by going too fast. For that reason, the decision I have 

 reached for myself * * * is that it would be much better as of now, for the manu- 

 facturing companies to stop further production of this current vaccine with the 

 dangerous strains, and immediately get to work * * * to see whether or not they 

 can produce antigenically equally as good vaccine with the other strains which 

 are now available.™ 



Eepresentative "Wolverton pressed for an immediate vote of the panel 

 on the two issues : the use of the Mahoney strain and the continuation 

 or suspension of the program. Sabin stated his position, and inserted a 

 letter agreeing with him from Dr. W. McD. Hammon, a panelist from 



wibid., pp. 150-158. 

 '* Ibid., p. 171. 



'■> iDia., p. IV 1. 



7» Ibid., pp. 162-166. 



wibid., p. 170. 



