The purpose of this study is to determine if a new cytomegalovirus (CMV) vaccine (CMV gB/MF59) can safely prevent mothers from catching CMV infection between pregnancies. This study includes 464 women, ages 14-40 years, who delivered a newborn infant within 12 months prior to the study. Participants must live within the Birmingham metropolitan area or the Tuscaloosa county area and they cannot have had CMV infection previously. CMV vaccine or placebo (substance containing no medication) will be given at 3 study visits. Participants fill out diary cards for 7 days after each vaccination. Blood samples will be collected. Urine samples will be collected several times and pregnancy tests will be performed. Participants who tested positive for CMV will have urine, vaginal swab, and saliva specimens collected. Each participant will be followed for 3 years after the third dose of vaccine. Infants born to participants in the study will be checked for CMV infection.