the Clincal stdies was conducted separately i.e., phase 1,2&3 trails for vacine to prvent Staphylcocus aures infetions.

For this 3 studies ie phas1,2,3 what r key distinction betwen objectves/endpionts & patient populatoins & why r tthey diferent?

Answer from the viewpoint of how this studieess fit into overal clnical develpmemt prgram.