All immunization and sampling procedures will be performed in Ahmed Maher Educational Hospital ( MOH). Subject enrollment, consenting, vaccination, sampling and clinical observation post vaccination will be done under close medical supervision by trained clinicians in the hospital. Seven blood samples will be taken from subjects prior to the first immunization and at days 30, 60, 90 ( during vaccination period) and days 135, 180 and 360 thereafter. At day 360 subjects will be immunized with a booster dose equal to the original dose given to the same subject and an 8th blood sample will be collected 30 days after the booster dose. Each time 15 ml venous blood will be withdrawn. Eight ml will be used for serum separation for humoral response determination, neutralization assays and biochemical testing. Seven ml on EDTA for CBC and lymphocyte separation for EliSpot assay.