STEPHANIE NEBEHAY and EMMA FARGE THE World Health Organization on Friday approved the emergency listing of Johnson & Johnson's COVID-19 vaccine, giving its seal of approval to expedite use especially in countries with weaker regulatory agencies. It is the third COVID-19 vaccine after the two-shot regimens of Pfizer/BioNTech and AstraZeneca to receive backing from the WHO, and the first requiring just a single injection. The listing covers use in all countries, for roll-out of the vaccine facility COVAX and follows the European Medicines Agency (EMA) authorisation announcement on Thursday. "Every new, safe and effective tool against COVID-19 is another step…