While researchers often use data from health insurance systems to conduct observational studies, the authors of this research paper point out that you can also conduct randomized trials as well. You can randomly assign different levels of insurance coverage and then get claims data to evaluate how much difference there is, if any, in the levels of coverage. This approach is attractive because you do not need a lot of resources, and you can very quickly get a very large sample size. Since insurance data is collected for administrative needs rather than research needs, you have to contend with inaccurate or incomplete data, potentially causing loss of statistical efficiency or producing biased results. The authors offer some interesting examples of actual studies, propose new potential studies, and offer general guidance on how to conduct a randomized trial from health insurance systems.
Choudhry NK. Randomized, Controlled Trials in Health Insurance Systems. N Engl J Med 2017 (Sept. 7); 377: 957-964. Available at http://www.nejm.org/doi/full/10.1056/NEJMra1510058.