The delta variant of Covid-19 took the U.S. by surprise. Months after the first vaccines rolled out, Covid-19 infections surged as the delta variant overwhelmed the unvaccinated population and even broke through the immunity from the shots from Moderna, Pfizer and Johnson & Johnson. Now, the White House has a new plan to fight the delta variant, including booster shots and vaccine mandates. Here’s where we stand in the debate over booster shots, and in the fight against the delta variant.