Open McAfee interface. Assuming you have the new blue and white interface, click the PC Security tab and then look at the bottom and you will see Application Updates, click that. Then click Scheduled Scan Settings to expand.
Scroll down to where you can turn it off. Don't forget to click Apply then close the application.
(Click image to magnify)
Thank you for your response exbrit. When I open the vulnerability scanner dialogue, there is a line near the top that says "Next Scheduled Scan: None". In the vulnerability scanner settings under "scheduled scan settings" I have the "Do not set a scan schedule" button selected. The vulnerability scanner still runs every now and then, not sure how often, but at least every week.