Dr Gopi Patel recalls how powerless she felt when New York's Mount Sinai Hospital overflowed with Covid-19 patients in March.

Guidance on how to treat the disease was scant, and medical studies were being performed so hastily they couldn’t always be trusted.

"You felt very helpless,” said Patel, an infectious disease doctor at the hospital. “I’m standing in front of a patient, watching them struggle to breathe. What can I give them?”...