Reduction in burden of illness: a new efficacy measure for prevention trials

• Published in: Statistics in medicine Vol. 13; no. 18; p. 1807
• Main Authors: Chang, M N, Guess, H A, Heyse, J F
• Format: Journal Article
• Language: English
• Published: England 30.09.1994
• Subjects: Data Interpretation, Statistical; Diarrhea - epidemiology; Diarrhea - etiology; Diarrhea - prevention & control; Humans; Incidence; Models, Statistical; Primary Prevention - statistics & numerical data; Randomized Controlled Trials as Topic - statistics & numerical data; Rotavirus Infections - epidemiology; Rotavirus Infections - prevention & control; Sample Size; Severity of Illness Index; Treatment Outcome; Viral Vaccines
• ISSN: 0277-6715
• DOI: 10.1002/sim.4780131803

A new efficacy measure is developed for use in prevention trials of interventions which may affect both disease incidence and disease severity. We assign a severity score to each incident case and sum severity scores over all incident cases within each treatment group to create a burden-of-illness score for each treatment group. Efficacy is evaluated by the difference between the burden-of-illness per randomized subject in the two randomized treatment groups. Since the numbers of summands in each burden-of-illness score is a random variable, standard methods of analysis are not directly applicable. The asymptotic distribution and sampling properties of the net reduction in the burden-of-illness score are derived for trials designed to stop either after a fixed length of follow-up or after the occurrence of a fixed number of cases. We illustrate the method with data from a clinical trial of a human rotavirus vaccine.