A total of 316 employees met inclusion criteria: 176 from campus A and 140 from campus B. Of these employees, 20 (11.4%, 95% CI 6.7%–12.1%) from campus A and 19 (13.6%, 95% CI 7.9%–19.2%) from campus B were excluded because test results for the CD69 lymphocyte–activation assay were positive, indicating previous coccidioidal infection and current immunity (p = 0.55). This evidence concerns the gene CD69 and coccidioidomycosis.