Questions have been raised over the effectiveness of a coronavirus vaccine developed by Chinese drug maker Sinovac Biotech after a partner science institute in Brazil, where phase 3 clinical trials are under way, released lower-than-expected efficacy results for the vaccine.The Butantan Institute in Sao Paulo said the CoronaVac vaccine had a roughly 50 per cent general efficacy rate – well below the 78 per cent reported earlier.So what do the numbers mean?Is CoronaVac still effective?The…

This post was originally published on South China Morning Post.