Even if these new characteristics merely modify the numerical relationships among the variables recorded, she will still have to retrain herself and learn a new prediction function all over again. That’s all that a deep-learning program can do: fit a function to data. On the other hand, if she possessed a model of how the drug operated and its causal structure remained intact in the new location, then the estimand she obtained in training would remain valid. It could be applied to the new data to generate a new population-specific prediction function.
