This quote is suggesting that a simple thing with few risks will lead to a terrible outcome, but there is no logical explanation for how mandatory vaccination would lead to harvesting organs from people. This is called a slippery slope fallacy. It is designed to make us fear something safe (like vaccines) by telling us that they will lead to something harmful (like harvesting our organs). But there is no logical reason to believe that this would happen.
Click here to see more examples of the Slippery Slope fallacy.