unit 9 pt 2 - 1950's Salk's Polio Vaccine Trial Salk's...

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Unit 9. Introduction to Experimental Studies/ Experimental Studies/ Intervention Studies - Part 2 ± Randomized Clinical Trials Community Trials ± Dr. Aurora Sanchez-Anguiano Epidemiology 6000 NO AUDIO ON THIS SLIDE 1950's Salk's Polio Vaccine Tria 1950's Salk's Polio Vaccine Trial Field trial in 600,000 school children. What's interesting . .. is that ² in some communities (N=84 test areas in in some communities (N=84 test areas in 11 states) children in grades 1-3 were randomized to receive vaccine or placebo randomized to receive vaccine or placebo ² and some (N=127 test areas in 33 states) weren't In these communities 2nd graders weren't. In these communities, 2nd graders received the vaccine while grades 1 &3 did not not. 1950's Salk's Polio Vaccine Trial: results In the randomized communities the In the randomized communities, the results were crystal clear. The vaccine protected against polio In the non protected against polio. In the non- randomized communities, results, though still slightly in favor of vaccine though still slightly in favor of vaccine, were much more ambiguous and would not have allowed investigators to not have allowed investigators to conclude that the vaccine worked. Why? We’ll never know for sure Why? We ll never know for sure. Alternatives to Randomization: Why don't they work? ² Historical controls: you compare your study patients with information on previous patients, taken from patient records or the literature. Copied From Pocock Clinical Trials: There ² Copied From Pocock-Clinical Trials: There are two major sets of problems with historical controls ² Problem Set 1. Patient selection ² Problem Set 2 Experimental Environmen Problem Set 2. Experimental Environment 1. A historical control group is less likely to have clearly Patient Selection defined criteria for patient inclusion, since such patients on standard treatment were not known to be in the clinical trial when their treatment began. (historical controls would tend to be less healthy) 2 Since historical controls were recruited earlier and 2. Since historical controls were recruited earlier and possibly from a different source, there may be a change in the type of patient available for selection. 3.There is danger that the investigator may be more restrictive in his choice of patients for a new treatment. (historical controls would tend to be more healthy). Experimental Environmen 1. Quality of historical data is inferior. A clinical trial Experimental Environment requires data entry and case report forms. 2. Outcome definition may differ between the two groups of patients groups of patients. 3. Ancillary patient care may improve on the new treatment. It is difficult to assure that all aspects of managing the patient, other than treatment, remain constant.
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This note was uploaded on 07/15/2011 for the course PHC 6000 taught by Professor Staff during the Summer '08 term at University of South Florida.

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unit 9 pt 2 - 1950's Salk's Polio Vaccine Trial Salk's...

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