EPIDEMIOLOGY OF PNEUMONIA 481 



each at weekly intervals. His results were distinctly encouraging, 

 though inconclusive. Cecil and Austin 94 did some experiments at 

 Camp Upton in which they vaccinated 12,519 men against types I, II, 

 and III, and their results also were encouraging, but again uncon- 

 vincing. The problem is sufficiently advanced to encourage wholesale 

 use, if conditions exist under which careful comparison 'with unvac- 

 cinated controls can be made. It cannot, however, be regarded as 

 definitely established as a prophylactic measure in the same way that 

 we may regard typhoid vaccination. At times of epidemic it should be 

 employed on as large a scale as possible, whenever possible, since only 

 in this way will we be able to judge of its value eventually. The 

 experiment can be done without harm, since the use of the vaccine is 

 contra-indicated only in acutely sick individuals, in pulmonary tuber- 

 culosis and nephritis, in patients with chronic heart disease, and Cecil 

 states also in pregnant women. 



The vaccines which so far have been used consist of culture sus- 

 pensions in salt solution killed by heating at 56 C., for one-half hour, 

 and standardized either by counting against red blood cells or by 

 means of the nephelometer. 0.3 per cent tricresol may be added to 

 preserve the suspensions which are made up so that about one thou- 

 sand million pneumococci are contained in 1 c.c. The dosage advised 

 by Cecil is three billions for the first dose, six billions for the second 

 and nine billions for the third. 



Lipo-vaccines which consist of pneumococcus suspensions in olive 

 oil and other vegetable oil mixtures have been used, but the method 

 of preparing these vaccines has not been satisfactorily perfected. 



84 Cecil and Austin, Jour. Exper. Med., 28, 1918, 19. 



