The phrase “new and daring” is not often paired with the words “healthcare intervention”, but this idea goes beyond eye-catching: young Tanzanians are to be bribed to stay HIV negative.

A consortium that includes the William and Flora Hewlett Foundation and the World Bank is funding the experiment. Several thousand 15 to 30-year-olds in rural Tanzania will be given advice on sexual health, regularly tested for infections, and paid almost $50 a year if the tests are negative.