A major British study into mixing Covid-19 vaccines has found that people had a better immune response when they received a first dose of AstraZeneca or Pfizer-BioNTech shots followed by Moderna nine weeks later, according to the results on Monday.

"We found a really good immune response across the board..., in fact, higher than the threshold set by Oxford-AstraZeneca vaccine two doses," Matthew Snape, the Oxford professor behind the trial dubbed Com-COV2, told Reuters...