LONDON—Britain said on Thursday that global supply bumps meant its vaccine rollout would be slower than hoped in coming weeks, but it expected deliveries to increase again in May, June, and July. British health officials warned on Wednesday that the world’s fastest big economy rollout of the vaccine would face a significant reduction in supplies from March 29, though they did not say where the problems were. Pfizer Inc and AstraZeneca Plc said their delivery schedules had not been impacted, and Housing Secretary Robert Jenrick refused to be drawn on whether the issue was due to a problem with supply from India. “We have less supply than we might have hoped for the coming weeks, but we expect it to increase again later,” Jenrick told the BBC. “The vaccine rollout will be slightly slower than we might have hoped but not slower than the target,” he said. “We have every …