Driving the news: A study published yesterday in Nature found that antibodies in people who had recovered from COVID were significantly less potent against Delta than the Alpha variant that first detected in the U.K. One dose of a vaccine, however, significantly boosted their response. Further, antibodies from people who had received only one dose of the Pfizer or AstraZeneca vaccines "barely inhibited" Delta, but two doses generated an effective response in 95% of people. Between the lines: Some public figures — like Sen. Rand Paul — have pushed the idea that people previously infected with the coronavirus don't need to be vaccinated.