Lesotho trial: lottery tickets for staying STI-free cut HIV infections 21.4%

In May 2015 NPR reported a study run by a World Bank-funded team in Lesotho, where, it says, 40% of people aged 30 to 34 are HIV-positive. Researchers recruited 3,427 volunteers in 29 villages to be tested every four months for two curable sexually transmitted infections. One group got small gifts for coming back.

The other group got a lottery ticket instead. Every four months, two men and two women in each participating village won a $50 prize, a lot of money in Lesotho. After two years there was a 21.4% reduction in HIV infections in the lottery group compared with the gift group, which researcher Martina Bjorkman Nyqvist called very large. Among volunteers who liked gambling, measured by a game, the reduction was about 60%.

The volunteers were tested for curable infections, not HIV, so that participants already HIV-positive would not be excluded. Nyqvist suggested a cheaper variant that drops most testing: give everyone a ticket and tell them any prize is paid only if they test negative for HIV.

A lottery appeals most to risk-lovers, the people hardest to change.

A prize is a large payoff relative to a small stipend; $50 is a lot of money in Lesotho.

Testing only for curable infections gave a cheap check on safe behavior.

The same hope of winning that drives lottery play is pointed at staying safe.

Use the target group's own risk appetite as the incentive: a lottery rewards the behavior you want from the people hardest to reach.

NPR notes it was too soon to roll the approach out widely and that the study needed to be replicated. It says the main cost would be the infection tests, which Nyqvist's proposed variant would cut.