My husband's WBC was down to 2.3 during treatment. It came back up to 3.5 and that is basically where it has stayed for the past 3 1/2 cancer free years. Oncologist told us sometimes it just never goes back up, not to worry. Remarkably in the past 3 1/2 years my husband has had only one minor cold, nothing else. While my three children have had numerous colds and stomach viruses.