In addition, an interim analysis is proposed for the primary endpoint for potential early study termination if there is overwhelming evidence that vaccine is less efficacious than IG. The Independent Data Monitoring Committee (IDMC) will be responsible for making the recommendation on whether or not to continue the study based on the results of the interim analysis and relevant safety data. The interim analysis will be performed when 14 (~50%) of the 28 expected cases of laboratory-confirmed clinical hepatitis A have been observed. Using the same assumptions that were used for the original power calculation, the probability of meeting the success criteria at the end of the study conditioned on the number of cases that were observed in the vaccine group for the interim analysis will be calculated. If the probability is 20% or greater that vaccine will meet the assumed statistical criteria by the end of the study, then the study will definitely continue. In addition, if after 12 months from study start, very few cases have been observed, the IDMC will assess the need for study termination.