EDWARD MCALLISTER and JENNIFER RIGBY CLUTCHING an umbrella, medical records and her two-year-old daughter, Kani Fall negotiated the brown puddles lapping at the hospital gate, the final hurdle in a two-hour, rain-soaked journey to her nearest vaccination clinic in the western Gambia. Fall waited with dozens of mothers and babies in the flooded courtyard of Bundung Hospital. Then a doctor emerged with bad news. The hospital had run out of measles vaccines, and it wasn't clear when they would receive more. "They told me there was no vaccine. But I am coming back," said Fall, 27, who had closed her…