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SCIENCE 



[N. S. Vol. XLIV. No. 1126 



Another improvement we have suggested 

 is the administration of the customary three 

 doses of vaccine within a week instead of 

 the three weeks usually regarded as neces- 

 sary. Here again careful experiments in 

 rabbits showed us that this rapid method 

 produces an equally efficient and lasting 

 protection. 



The final proof of the value of a prepara- 

 tion is of course in practise, that is to say, 

 its actual protective value for human beings. 

 The California State Board of Health has 

 been supplying our vaccine for free dis- 

 tribution to physicians for the past two 

 years. Dr. Sawyer, of this board, under- 

 took to find out the results of typhoid vacci- 

 nation in this state about a year ago. He 

 obtained records from over 5,000 cases that 

 had been treated with our vaccine, and 

 something over half that number that had 

 been treated with various other vaccines, 

 mostly of the army type, as dispensed by 

 commercial houses. There were about the 

 same actual number of failures to protect 

 in both series, that is, there were twice as 

 many cases of typhoid fever per thousand 

 among those vaccinated with other vaccines 

 as with our own. 



It is evident, then, from these results and 

 from what I have said, that typhoid vacci- 

 nation, at least in the general community, 

 is relatively, but not absolutely, protective. 

 It remains for future investigation to deter- 

 mine in what way the percentages of fail- 

 ures can be decreased. 



It seemed to us very important, in our 

 investigations, to devise a method by which 

 the duration of protection could be deter- 

 mined in individual cases. It is all very 

 well to know that on the average vaccina- 

 tion will protect for about two years, but 

 what of the exceptional individual, who 

 from sad experience we have learned is not 

 protected even for two months ? Dr. Force 

 and I think we have a method for deter- 



mining the actual presence or absence of 

 protection in the individual at any given 

 time. This tests consists in rubbing a small 

 amount of material from killed typhoid 

 bacilli on the skin. We have found that 

 nearly all those who have had typhoid fever 

 in the past, and who are known to be usually 

 protected from it, react to this test with the 

 formation of a slight reddish blush about 

 the abrasion. Most people who have been 

 vaccinated within the last two years also re- 

 act positively. Normal people do not react. 

 We feel justified in assuming that the pres- 

 ence of a positive reaction of this sort is 

 evidence of protection. So far it has not 

 failed us in practise, that is to say, no vacci- 

 nated person who has given a positive test 

 has shortly thereafter had typhoid, and 

 conversely in two vaccinated cases where 

 the tests were negative and doubtful, re- 

 spectively, the individuals have shortly 

 thereafter contracted typhoid fever. It is 

 too early to speak authoritatively about the 

 absolute value of this "typhoidin test," as 

 it is called, but at least we feel justified in 

 urging our vaccinated students to be re- 

 vaccinated when we find the test negative. 



I hope I have somewhere in my remarks 

 suggested to you that results of direct prac- 

 tical bearing are by no means always ar- 

 rived at directly. In fact the experienced 

 investigator comes to rely more and more 

 on Pasteur's adage of "Chance and the 

 Prepared Mind, ' ' and learns to seize chance 

 happenings and turn them to his own ends. 

 I think the evolution of a practical point 

 out of theoretical studies may well be illus- 

 trated by some of our recent work. The 

 efficacy of various typhoid vaccines has been 

 tested, as already mentioned, by the ability 

 of each to protect rabbits in a given dose 

 for a given number of weeks against infec- 

 tion with a large dose of living typhoid 

 bacilli. In unprotected animals, or in ani- 

 mals insufficiently protected, these injected 



