Among children without confirmed Giardia infection in diarrheal stools, seroprevalence to VSP-3 or VSP-5 antigens increased from 1% (95% CI: 0%, 5%) at enrollment to 22% (14%, 32%) at follow-up; among children without confirmed Cryptosporidium infection, seroprevalence to Cp17 or Cp23 antigens increased from 16% (10%, 24%) at enrollment to 47% (37%, 57%) at follow-up. The gene discussed is CEMP1; the disease is cryptosporidiosis.