chief medical adviser said he expects US regulators to consider whether people who got the one-dose Johnson & Johnson vaccine should get an mRNA shot against Covid-19 as a booster. “If you boost people who have originally received J&J with either Moderna or Pfizer, the level of antibodies that you induce in them is much higher than if you boost them with the original J&J," Anthony Fauci said on ABC’s “This Week" on Sunday. “But the data of boosting the J&J first dose with a J&J second dose is based on clinical data," he said. “So what’s going to happen is that the FDA is going to look at all those data, look at the comparison, and make a determination of what they will authorize." A so-called mix-and-match booster has been discussed