Covid-19: How do you calculate herd immunity?

Herd immunity represents the percentage of people in a population who need to be immune to a disease in order to protect those who aren’t. Early on in the pandemic, researchers estimated the herd immunity threshold for Covid-19 to be 60%. Following a question from a listener, Ian Sample speaks to Rachel Thomas to explore the maths and find out exactly how herd immunity is calculated. Help support our independent journalism at