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Efficiency of Estimating Vaccine Efficacy for Susceptibility and Infectiousness: Randomization by Individual Versus Household
Author(s) -
Datta Susmita,
Halloran M. Elizabeth,
Longini Ira M.
Publication year - 1999
Publication title -
biometrics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.298
H-Index - 130
eISSN - 1541-0420
pISSN - 0006-341X
DOI - 10.1111/j.0006-341x.1999.00792.x
Subject(s) - randomization , placebo , restricted randomization , transmission (telecommunications) , medicine , statistics , randomized controlled trial , computer science , mathematics , telecommunications , alternative medicine , pathology
Summary. In designing vaccine efficacy studies based on the secondary attack rate (SAR) or transmission probability in which both vaccine efficacy for susceptibility, VE S , and vaccine efficacy for infectiousness, VE I , are estimated, the allocation of vaccine and placebo within transmission units has an important influence on the efficiency of the study. We compared the following randomization schemes that result in different allocations of vaccine and placebo within two‐member households: (1) randomization by individual for a mixed allocation, (2) randomization by transmission unit for concordant allocation, and (3) randomization of only one individual in each transmission unit to either vaccine or placebo. There is a complex interaction among the VE S , VE I , and the SAR that determines which allocation of vaccine and placebo within households provides the most information. In general, individual randomization with a mixed allocation of vaccine and placebo is better for estimating both VE S and VE I than is randomizing by household. However, for estimation of VE I , at very low SARs and low VE S , randomization by household is slightly more efficient than randomization by individual.