The study design followed the guidelines published by the European Medicines Agency (EMA) as well as other relevant guidelines (EMEA 1995 (EMEA , 2000 WHO 2005) . All experiments were performed under good laboratory practices (GLP) conditions. Animals were inoculated and monitored at the laboratories of the Centre International de Toxicologie (CIT; Evreux, France). Of the 42 monkeys included in the study, 18 young males and 18 young females were allocated to treatment groups 1-6 (Table 1) . Animals were allocated to groups (by sex) using a computerized randomization procedure (CITOX software, developed in-house at CIT, Evreux, France). In addition, six sexually mature males (three per group) were allocated to treatment groups 7 and 8 using the same randomization procedure, and were only used for collection of semen and peripheral blood mononuclear cells (PBMC), as well as for selected clinical observations (body weight, body temperature and food consumption). Treatments included 3.9 × 10 3 CCID 50 of Rouvax, 1.6 × 10 4 CCID 50 of MV1-F4 vaccine, or saline, and were administered according to either a one-dose schedule (injection at day 1) or a three-dose schedule (injections at days 1, 29 and 57). Monkeys were monitored clinically until sacrifice (groups 1-6) or until return to laboratory stock at day 85 (groups 7 and 8). Upon completion of the observation period, animals of groups 1-6 were sedated with ketamine hydrochloride (Imalgène, Mérial, Lyon, France), then anesthetized with thiopental and sacrificed by exsanguination. Necropsy was performed at two time-points, either within the expected peak of viremia (10 days after the first vaccine dose (day 11) for groups 1-3) or when clearance of infectious MV was expected to have occurred (represented by 28 days after the third dose [day 85] for groups 4-6) (Auwaerter et al. 1999; Pan et al. 2005; Permar et al. 2003) . Single-and repeated-dose toxicity was assessed at various time points (Table 2 ). Shedding and post-mortem analyses were conducted at Texcell (Evry, France). All other procedures were conducted at CIT.