Philadelphia Inquirer: What We Learned From Philadelphia’s Vaccine Lottery

Earlier this month, the Food and Drug Administration and the Centers for Disease Control and Prevention authorized new COVID-19 booster vaccines with the hope of staving off another wave of hospitalization and death this winter. Invaluable as vaccines have been in the fight against COVID, only one in three American adults chose to receive the last round of lifesaving booster shots, which helps explain the nearly 500 daily deaths that are still being recorded in this country.

We recently published a paper in Nature Human Behavior summarizing what we learned from the Philly Vax Sweepstakes — a vaccine lottery with prizes worth up to $50,000 that was designed, implemented, funded, and evaluated by our research team at the University of Pennsylvania and carried out in partnership with the city of Philadelphia. In 2021, at least 21 states sponsored vaccine lotteries in which only vaccinated residents were eligible to win large prizes.

We developed the Philly Vax Sweepstakes to answer two policy questions: Could vaccine lotteries be effectively targeted at zip codes with especially low vaccination rates? And could a well-designed citywide lottery cost-effectively boost vaccinations in Philadelphia compared with surrounding communities?

Building on prior research, our sweepstakes was designed as a “regret lottery.” This means every adult in Philadelphia was automatically entered. However, prizes could only be collected by those able to prove they’d been vaccinated before their name was drawn.

Drawings took place three times over six weeks for a total of 36 prizes. Two weeks before each drawing, we randomly picked one of Philadelphia’s 20 zip codes with the lowest vaccination rates and announced that in that zip code, residents would receive half the prizes from the next drawing. Compared with other Philadelphians, residents of these zip codes had 50 to 100 times the chance of winning a cash prize.

So what did we learn? A surprising number of Philadelphians were paying attention and wanted to win.

Even though we announced that residents were automatically entered in the sweepstakes, one in 16 Philadelphians took the time to confirm their contact information was in our system over the course of the lottery. Philadelphians in the zip codes with inflated odds of a win were particularly eager to reconfirm their contact information. Despite this flurry of excitement, we’re confident that giving select zip codes higher odds of a sweepstakes win did not increase the adoption of vaccines in those zip codes.