How effective would a data-driven vaccination program be over a simple rules based approach
The reason for the rules based approach is the simpson paradox.

In short, the way a test group is sampled can easily overturn the conclusion of a study. It is very important to include sufficient patients from a particular risk group in the study.
This is why rules are set.
This approach however is the basis of causality theory. A data driven-approach would be as followed:

experts flag expected causal patterns, i.e. draw causal graph of the study. [This is the mathematical formulation of risk factors]
Causal graph generates ideal distribution of study and tools to draw conclusion