Prognosis
Delta Seen to Push Herd Immunity Threshold Above 80%
- Highly contagious strain raises bar for limiting infections
- Virus experts say more transmissible variant shifts goalposts
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The spread of the delta coronavirus variant has pushed the threshold for herd immunity to well over 80% and potentially approaching 90%, according to an Infectious Diseases Society of America briefing on Tuesday.
That represents a “much higher” bar than previous estimates of 60% to 70%, because delta is twice as transmissible, said Ricardo Franco, an assistant professor at the University of Alabama at Birmingham.