evidence: The mRNA vaccine from Pfizer and BioNTech may be less effective than Moderna's against the Delta variant of the coronavirus, according to two reports posted on medRxiv on Sunday ahead of peer review. In a study of more than 50,000 patients in the Mayo Clinic Health System, researchers found the effectiveness of Moderna's vaccine against infection had dropped to 76% in July - when the Delta variant was predominant - from 86% in early 2021. Over the same period, the effectiveness of the Pfizer/BioNTech vaccine had fallen to 42% from 76%, researchers said. While both vaccines remain effective at preventing COVID hospitalization, a Moderna booster shot may be necessary soon for anyone who got the Pfizer or Moderna vaccines earlier this year, said Dr. Venky Soundararajan of Massachusetts data analytics company nference, who led the Mayo study. (Aug. 9) [...] New research offers encouraging evidence about how the Johnson & Johnson vaccine stacks up against its competitors — and the delta variant — according to infectious-disease specialists. However, there are still lingering questions about booster shots. Earlier clinical trials showed the Johnson & Johnson vaccine was 66 percent effective overall in preventing moderate to severe disease four weeks after the shot, with effectiveness varying depending on location. Its competitors from Pfizer and Moderna, on the other hand, recorded 90 percent-plus effectiveness against the coronavirus. Anthony S. Fauci, the nation’s leading infectious-disease expert, has said all three vaccines are effective. (Beachum, Bever and Iati, 8/10)