CURRENTLY there are several candidate rubella vaccines being evaluated in various populations.1,2 The vaccines are live, attenuated, high-passage viral preparations, differing in the cell type used for propagation, but apparently quite similar in their behavior in humans. The Clinical Virology Section (CVS) at the University of Cincinnati Medical Center has been involved in a series of closed adult population studies which evaluated the effects of several of the vaccines (G.M.S., unpublished data). Our findings, which confirmed the reports of other investigators,1-5 showed that the vaccines were antigenic, safe, caused few symptoms or signs, and were incapable of spread to contacts. These results indicated that vaccine evaluation could safely proceed to larger and open populations. A number of open-population studies have been and are being conducted.5-7 Preliminary reports from these studies reinforced the earlier closed-population results and indicated that the vaccines were effective and safe for evaluation in