426 SMALLPOX AND ITS CONTROL 



check. A vaccination against smallpox lasts from five to seven 

 years. After that time there should be a second vaccination. 

 The second vaccination may produce immunity for life. By im- 

 munity is meant the ability to resist disease. All children should 

 be vaccinated before they are nine months old. Vaccination 

 during epidemic periods is also wise. 



The vaccine for smallpox is prepared by first developing the 

 causative organisms in the body of young female calves. After 

 determining that the calves are perfectly healthy, they are 

 thoroughly cleaned and usually inoculated with the virus of other 

 calves. Cysts or vesicles are formed at the site of the vaccination 

 in about five or six days and the contents of these vesicles are 

 scraped off and ground into dilute glycerine in order to destroy all 

 harmful bacteria. This product is then tested several times, in 

 many ways, for purity as well as for effectiveness. The material 

 is then put up in small tubes ready for use. 



Value of vaccination. The gradual disappearance of smallpox 

 is due largely to the widespread use of vaccination. In coun- 

 tries where vaccination is not required, smallpox is still causing 

 the deaths of thousands of people each year. It is still one of 

 the main causes of death in China and India. Between the 

 years 1918 and 1922, India reported 63,553 deaths from this 

 disease alone. In Russia, between the years 1902 and 1914, over 

 a milhon persons became affected with smallpox and over half 

 a million died of it. 



In the Philippine Islands, prior to the occupation by the Amer- 

 ican Armv, it was estimated that more than 40,000 smallpox 

 deaths occurred annually. Vaccination was introduced by the 

 Americans in 1905, and has been continued ever since. There were, 

 in 1903, 18,989 smallpox deaths, but this number has decreased 

 rapidly until in 1916 only 239 deaths occurred from this disease. 

 Then the effects of the first vaccinations wore off and people be- 

 came careless about being revaccinated. This neglect resulted in a 



