Well, if it's the standard deal with a demon, then it delivers the goods, but has a brutal cost and lasts for a limited period of time; and there's an option to walk away, but it means facing something worse than if you had never made the deal. Hmm: this could actually fit rather well.

The vaccines do seem to prevent severe outcomes from Covid-19, but only temporarily. So at each junction people have the option to walk away, but if these vaccines have the common coronavirus vaccine side effect of ADE, by accepting a much higher risk of severe disease from Covid, possibly for the remainder of their life.