The delta variant is at least 40 percent more infectious, Health Secretary Matt Hancock said Monday, and it is quickly becoming the dominant strain in Britain — outpacing the variant first discovered in southeastern England that became ubiquitous in Europe and the United States. Cases of the delta variant are now doubling every eight days. Is the delta variant deadlier? Does it make people sicker? Unclear. Will it resist the current arsenal of vaccines deployed in Britain — the AstraZeneca, Pfizer and Moderna shots? Unknown. Early laboratory studies and clinical data suggest it may resist the vaccines a little bit, and people who have been only partially vaccinated may be vulnerable. But hospitalizations are still low, and ICU beds across the National Health Service system are mostly empty of coronavirus cases. On Monday, England recorded just a single death from the virus. That makes it harder to tell the British people they need to wait.