WHO is saying that it is approached by around 40 different groups that attempt to develop Coronavirus vaccine so far. Not all are promisng. Even those that sounds promsing takes months to come out with a result. An offical of WHO on his interview with CNN on 24th of March 2020 confirms the attempts so far and how difficult it is to say anything concrete at this moment.
A human test started in USA on coronavirus vaccine. WHO is closely following trials to develop coronavirus vaccine around the world.