Immunization warning on open browsers (Spybot - Search & Destroy 2)

If a browser is opened, it already has the current immunization lists in memory, and might commit an old state back to disk when it is closed. It is therefore recommended to close the browser or browsers displayed in this dialog before taking any immunization action.

Immunization is intended as a pro-active action, which means it is not time critical. Better to complete anything you're currently working on in your open browser windows before continuing to immunize, than having an incomplete immunization result.