One of the main purposes of the CAPA process is to systematically reduce risk. Many people think the CAPA is done once the action itself is complete, without verifying that the steps taken actually reduce risk to acceptable levels.
Performing a risk assessment as a final effectiveness check is what tells you whether you can close it out, or whether you need to take additional action. This is the key ‘check’ step in the plan-do-check-act cycle of continuous improvement.