On Monday, the world heard how the UK's Covid vaccine - from AstraZeneca and Oxford University - was highly effective in advanced trials.

Axar.az reports that it gave hope of another new jab to fight the pandemic that should be cheaper and easier to distribute than the Pfizer/BioNTech and Moderna mRNA vaccines that announced similarly impressive results just days before.

But after the jubilation, some negative press has followed.

On Thursday, multiple news outlets in the UK and the US reported that there were questions over the data. They weren't about safety, but rather how effective the jab is.

The questions center around efficacy levels.

Three were reported from the trial - an overall efficacy of 70%, a lower one of 62%, and a high of 90%.

That's because different doses of the vaccine were mistakenly used in the trial. Some volunteers have given shots half the planned strength, in error. Yet that "wrong" dose turned out to be a winner.