New Delhi, Oct. 12 -- It was during the early months of the pandemic, and Donald Trump was vexed. Experts had told him that hydroxychloroquine, a malaria drug, was no good as a treatment for covid-19. He summoned Francis Collins, the head of the National Institutes of Health, to put him straight. The president had compelling anecdotal evidence. "Get me Jack Nicklaus!" he shouted to a flunkey. Mr Nicklaus was an 80-year-old ex-professional golfer. He had caught covid, taken hydroxychloroquine and recovered, he told Dr Collins. "There, you see!" said Mr Trump. "You see!"

Dr Collins, who discovered the gene for cystic fibrosis, tried to respond tactfully. No disrespect to Mr Nicklaus, arguably the greatest golfer in history, but most people...