the verb prevent (to preclude, stop, hinder) originally was used in the sense(s) of to prepare, anticipate, precede, or to go before with spiritual guidance and help:

Prevent us, O lord, in all our doings, with thy most gracious fauour, and further us with thy continual help....

Preventive medicine appears to get a bit of sense from nearly all those senses of the verb: preparation and aniticipation coupled with preclusion and hindrance. In fact, preventive medicine is more focused on preparation.

But, I will admit, the text you've provided, tsuwm, is one I'd misread and am thankful to have your clarification. The text makes little sense when read with the newer shift in meaning.