We have all had reasons to envy India of late. Not only are they beating us at cricket. The Test was watched by proper crowds, like the good old days.

And then there’s Covid. Their daily infection rates have shrunk from 100,000 a day to fewer than 10,000 – without a mass vaccine rollout or the universal wearing of masks.

And it’s not down to a lack of testing. Back in November, around 90% of Delhi’s intensive care beds with ventilators were full. Today it’s just 16 percent. So what’s going on?

Scientists baffled as India’s Covid cases tumble