Source: United States & Canada – South China Morning PostThe spread of the Delta coronavirus variant has pushed the threshold for herd immunity to well over 80 per cent and potentially approaching 90 per cent, according to an Infectious Diseases Society of America briefing.That represents a “much higher” bar than previous estimates of 60 per cent to 70 per cent, because Delta is twice as transmissible, said Richard Franco, an assistant professor at the University of Alabama at Birmingham.“It is becoming clear that this is a very dangerous, way more…Read More