Statistical analysis of the rate of recurrence of herpesvirus ocular epithelial disease

We studied prospectively the rate of recurrence of epithelial herpetic disease in patients with at least two previously documented episodes of herpes. The estimate of probable recurrence was 24.5% +/- 4.8% within 12 months and 32.9% +/- 6.5% within 24 months. We found no significant correlation between rate of recurrence and either the age or the sex of the patient. However, the length of time between the two attacks suffered before the study was significantly associated with the length of the interval between entering the study and the next recurrence. Short intervals between previous attacks tended to be associated with short intervals between future attacks, and, therefore, with a higher recurrence rate. By eliminating a given patient from the study after one recurrence, we avoided serious biasing.