However, the 90% claim came into question after it was pointed out the vaccine’s overall efficacy was 62 to 70% in trials in Brazil and in the UK, while the 90% figure was reached only among fewer than 3,000 UK participants who were given a lower dose as a result of an error. Researchers can’t explain why the accidental lower dose proved more effective. So AstraZeneca plans to run another trial, testing just this lower-dose regimen. “Now that we’ve found what looks like a better efficacy we have to validate this, so we need to do an additional study,” Soriot told Bloomberg. He said that because the efficacy is high, a smaller number of patients would be needed.
Age issues: There are also concerns that the low-dose trial didn’t include anyone over the age of 55, so this second trial should give researchers the chance to confirm the vaccine’s