Coronavirus: Delta’s spread could push herd immunity threshold above 80 per cent
- Delta variant twice as transmissible, more dangerous than the original virus
- Covid-19 shots targeting Delta may be needed, researchers in England say
The 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 dangerous virus than the original one,” Franco said on Tuesday.
Herd immunity is based on the idea that when a certain percentage of the population has been vaccinated against the virus or gains immunity by a previous infection, it helps protect the broader population and reduce transmission.
Since it began in late 2019 the coronavirus outbreak has killed at least 4.2 million people globally, including 613,679 people in the United States, which is the worst-affected nation.
The availability of vaccines saw the daily toll of new cases drop dramatically in many countries earlier this year, but the highly contagious Delta variant, first identified in India, has since been driving surging infections.