| Popis: |
The rationale for large-scale use of any vaccine in the prevention of an infectious disease lies in the demonstration of its effectiveness in man. Uncontrolled observations of the effect of vaccines in the field may be misleading; therefore, properly designed controlled field trials are required for their evaluation. In the past, most authors did not consider this type of study essential for evaluation of the efficiency of vaccines, and, therefore, failed to set up field studies according to the principles of controlled field trials, which became widely recognized only recently [1]. |
