Followup: Return clinic visits will be scheduled on days 2, 7, and 28 after INF dose 1, at which times the diary card data will be recorded by staff and the card collected on day 28. Upon receiving dose 2 of vaccine, patients will be scheduled again to return to the study center 2, 7, and 28 days afterwards. The same procedures as for dose 1 regarding diary cards, telephone followup, and home visits will apply after dose 2.