If we can able to get vulnerability details using Burp Suite scanner in Qualys WAS(i.e. I believe Burp scanner scans automatically), then what is the need of doing automated scan in Qualys WAS as both do automated scan.
Qualys is an automated scanning methodology whereby you can define a web application and its scope, and run automated, scheduled scans against that application. Burp Suite Scanner, on the other hand, is intended to run with a user at the helm. The following is taken from the PortSwigger website:
Burp's preferred approach to scanning employs a different, user-driven paradigm. This gives you fine-grained control over each request that gets scanned, and direct feedback about the results.
Retrieving data ...