Elvira Zenaida Lansang,1 Kenneth Tan,2 Saumya Nayak,1 Ken J Lee,1 Karen Wai1 1Feasibility and Site Identification – Asia, Quintiles East Asia Pte Ltd, Singapore; 2National University of Singapore, Singapore Introduction: Conducting clinical trial feasibility is an important first step in initiating a clinical trial. A robust feasibility process ensures that a realistic capability assessment is made before conducting a trial. A retrospective analysis of vaccine clinical trials was performed to understand changes which could affect feasibility recommendations. Methods: Feasibilities conducted by Quintiles between January 2011 and August 2012 were reviewed. Vaccine studies only involving Asia–Pacific countries were selected, and common study parameters were identified. Information from Quintiles’ database was retrieved to examine changes in parameters over time. Results: A total of six vaccine studies were identified within the 1.7-year period. Two studies were excluded because they did not contain feasibility information or had involved sites that were sponsor selected. Four studies were analyzed. Three cases required healthy volunteers, while one case involved a specific patient population. Age requirement and seasonality of disease mainly influenced recommendations for Study 1. Sponsor’s marketing strategy influenced the recommendations for Study 2. Study 3 showed the effect of a country’s immunization program and reimbursement of vaccines on a study’s success. In contrast to the other studies, Study 4 demonstrated the impact of eligibility criteria in recruitment recommendations for a vaccine trial requiring specific patient pools. Conclusion: Feasibility recommendations for vaccine trials are largely based on (1) eligibility criteria; (2) cultural beliefs; (3) country’s past recruitment performance; (4) use of advertising; (5) site’s access to subject populations; (6) cooperation with local health professionals and government; (7) sponsor’s marketing strategies; (8) study design concordance with national immunization programs; (9) reimbursement of vaccines; (10) overall benefit of the vaccine to the population; and where applicable, (11) seasonality of the disease under study. Keywords: volunteers, recruitment, influenza, meningococcal, diphtheria, herpes zoster