Each age cohort of the study (Cohort I onwards) will be completed and based on the development, and progress, the next age cohort will be initiated. If the vaccine is found to be safe in the adults it will be tested in the children, 6-17 years of age and followed by the younger age group 1-5 years of age. The results will be presented to the Data Safety Monitoring Board after completing the 28-day safety surveillance part of each age cohort of the study and before proceeding to the next study age cohort.