Source: South China Morning PostBritish-Swedish drug maker AstraZeneca on Wednesday revised down by three percentage points the effectiveness of its Covid-19 vaccine after American authorities raised concerns that results reported from its US trial were outdated.The company now says its vaccine is 76 rather than 79 per cent effective at preventing any kind of symptomatic Covid-19.It remains 100 per cent effective against severe Covid-19, it added.British PM Boris Johnson gets first dose of AstraZeneca vaccineThe move came…Read More