Merck is currently testing two vaccine candidates (Sanofi is too actually). They started development later and took more time but when all will be said and done

Merck is currently testing two vaccine candidates (Sanofi is too actually). They started development later and took more time but when all will be said and done, I fully expect them to have shipped more vaccines than Moderna and Pfizer: mRNA-based vaccines have never been produced at scale and the logistic involved seems rather complexe. Merck and Sanofi are developing vaccines based on existing vectors. They can reach true mass production as soon as they get approved. It's the same thing for Johnson and Johnson actually. AstraZeneca has what I would call a true headstart however.