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 of the study.

"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.

The findings supporting flexible dosing will offer some hope to poor and middle-income countries which may need to combine different brands between first and second shots if supplies run low or become unstable.

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