https://www.wsj.com/articles/what-it-would-take-for-herd-immunity-to-stop-the-coronavirus-pandemic-11600594201
"Reflecting these real-world effects in disease models can shift the estimated herd immunity boundary. One group of researchers estimated that threshold for Covid-19 could be as low as 10% to 20%, though many epidemiologists say that is unlikely. Other modelers have estimated it at around 40% to 50%. Christopher Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington, said his group estimates the herd-immunity threshold at between 50% and 80%."