From The End of Asymmetric Information by Alex Tabarrok & Tyler Cowen:

The actual problems with health insurance markets have less to do with information asymmetry and adverse selection than with too much information. That can make some people’s insurance very expensive at actuarially sound rates. For instance if you have a cancer of a given kind, this is verifiable to the outside world, and if the treatment costs are $200,000, the cost of an insurance policy will in turn be about $200,000. Buying the policy won’t be cheaper than buying the treatments, and in that sense the market for insurance is not always present. That is a very real public policy problem … The cheap sequencing of the genome may accelerate and intensify these issues. …

https://www.cato-unbound.org/2015/04/06/alex-tabarrok-tyler-...