Condition: Carcinoma, Ovarian Epithelial

The primary objective is to compare pembrolizumab plus paclitaxel with or without bevacizumab to placebo plus paclitaxel with or without bevacizumab, with respect to progression-free survival (PFS) per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 as assessed by the investigator. The hypotheses are that pembrolizumab plus paclitaxel with or without bevacizumab is superior to placebo plus paclitaxel with or without bevacizumab, with respect to PFS per RECIST 1.1 as assessed by the investigator for participants with programmed cell death ligand 1 (PD-L1) positive tumors (Combined Positive Score [CPS] ≥1) and that pembrolizumab plus paclitaxel with or without bevacizumab is superior to placebo plus paclitaxel with or without bevacizumab, with respect to PFS per RECIST 1.1 as assessed by the investigator for all participants.