When will we know a vaccine works? More than half a dozen drugmakers around the world are conducting advanced clinical trials, each with tens of thousands of participants, and several expect to know if their COVID-19 vaccines work and are safe by the end of this year.The most optimistic timeline comes from AstraZeneca Plc , which is running a study in Britain that it says could be completed as early as August.Dr.
Anthony Fauci, the top US infectious diseases expert, told Reuters last week that a trial by Moderna Inc could produce decisive results by November or December.