Covid-19 vaccine, because the world needs it and for the potential pay day.Here's an update on the quest for a magic bullet against the coronavirus that has already killed more than a million people worldwide.How many in the pipeline? The World Health Organization (WHO) has identified 42 "candidate vaccines" at the stage of clinical trials, up from 11 in mid-June.Ten of them are at the most advanced "phase 3" stage, in which a vaccine's effectiveness is tested on a large scale, generally tens of thousands of people across several continents.US biotech firm Moderna, a US-German collaboration between BioNTech and Pfizer, several state-run Chinese labs, and a European project led by the University of Oxford and AstraZeneca are thought to be.