Medical Biomathematics and Biometrics Commons^™

Should Biomarker Estimates Of Hiv Incidence Be Adjusted?, Ron Brookmeyer

Ron Brookmeyer

Objective: To evaluate adjustment procedures that have been proposed to correct HIV incidence rates derived from cross-sectional surveys of biomarkers (BED). These procedures were motivated by some reports that the biomarker BED approach overestimates incidence when compared to cohort studies.

Design: Considered the Hargrove and McDougal adjustment procedures that adjust biomarker estimates of HIV incidence rates for misclassification with respect to the timing of infections.

Methods: Performed mathematical and statistical analysis of the adjustment formulas. Evaluated sources of error in cohort studies of incidence that could also explain discrepancies between cohort and biomarker estimates.

Results: The McDougal adjustment has no …

The Effects Of Herd Immunity On The Power Of Vaccine Trials, Blake Charvat, Ron Brookmeyer, Jay Herson

Ron Brookmeyer

We evaluate the effects of herd immunity on the power of vaccine trials. We consider large-scale trials in which persons are individually randomized to either placebo or vaccine. We evaluate the adequacy of naive power calculations that ignore the effects of herd immunity such as those based on the comparison of two independent binomials. We developed a simulation design to evaluate the quantitative effects of herd immunity on power. The simulation design accounted for nonhomogeneous mixing. We found that naive power calculations that ignore the effects of herd immunity can seriously overestimate power. In fact, we found that as sample …