Can anyone explain what happened with Astra Zeneca today? Why has it reportedly doubled in share price since Friday?

All morning, my portfolio was showing up 104-107% for this holding and then in the afternoon, it dropped to up only 2.5-3%, but the price went from in the $90's on Friday to over $190 today and didn't drop to reflect only 2-3% gain (it's still in the $190's per share). I can't find anything that explains what is going on, other than a brief blurb stating it was beginning to trade on the NYSE today from Fidelity.