Significantly Elevated CA 19-9 after COVID-19 Vaccination and Literature Review of Non-Cancerous Cases with CA 19-9 > 1000 U/mL.

Background: CA 19-9 is a commonly assessed tumor marker, considered characteristic of pancreatic ductal adenocarcinoma (PDAC) and biliary tract cancers; however, the positive predictive value of CA 19.9 is too low, and the usage of CA 19.9 as a screening tool in the healthy population remains controversial.