Health Check examines the excitement around the preliminary announcement of 90% effectiveness of BioNTech and Pfizer’s Covid-19 vaccine in its phase 3 clinical trial. Claudia Hammond talks to Professor Gregory Poland, head of vaccine research at the Mayo Clinic in the United States about what we do and don’t know about the vaccine at this stage, and how the vaccine may be approved and deployed in the coming months. She consults Kalipso Chalkidou, Professor of Global Health Practice at Imperial College London, about the challenges of getting this vaccine to people in low and middle income countries. One logistical problem is that the vaccine has to be stored at minus 80 degrees Celsuis. BBC medical and science correspondent James Gallagher also joins Claudia to explain the innovative nature of the vaccine and how its interim success bodes well for the development of other coronavirus vaccines. Presenter: Claudia Hammond Producer: Andrew Luck-Baker (Picture: Medications in sealed vials with a disposable plastic medical syringe. Photo credit: GIPhotoStock/Getty Images.)