But I think there’s a way that might work, a way that leverages human psychology. People like to feel like they’re in control, and they like to feel like they have a voice in the system. Micropayment systems that require you to pay 10 cents to read an article, based on a headline or a link, or subscription systems that take your money and give you something you can get elsewhere for free, just make you resentful. So instead, design the system so that you associate feeling good about what you have just read with giving money to the people who produced the content.
It could just be that people on the placebo took more risks than the people who didn't which is why it is a statistical outlier.
Why would they take more risks? The whole point of a placebo is that you don't know if it's a placebo or not. So there's no reason to expect a change in behavior in one group versus the other. In fact, the behavior change should be driven in the other direction. If there was some reason to think that you got the vaccine (say, side effects not present with the placebo), then you would be likely to increase your risky behavior and increase your likelihood of infection! In this case, they got an effect in the other direction -- the treated group had less infections.