by Paul RICARD and Jean-Philippe CHOGNOT Agence France Presse With several Covid-19 vaccines either being rolled out or under trial, here is a rundown of the various stages of their development. On the market: PFIZER/BIONTECH The mRNA vaccine developed by US pharma giant Pfizer and German start-up BioNTech is already approved for use in the European Union, the United States, Canada, Britain and several other nations. Clinical trials showed the vaccine — […]