Is there a particular vaccine in development that you have in mind? A quick google search doesn't suggesting any specific product.

Without knowing anything about a particular product, I'm very bearish on this for many reasons. To name a few:

- SCLC is much less common than NSCLC, so it's not the largest market share

- SCLC, and small-cell cancers in general, are a challenging disease space for drug development. They are historically very treatment-resistant, present few appealing antigenic targets, and many therapies have failed to work there, so it may be easier to show an effective product in other spaces (like NSCLC). This article describes some of the challenges well.

- Arguably, no cancer vaccine has ever been clearly shown to work, despite many attempts. At the academic medical center where I work, for instance, our several attempts to develop cancer vaccines have met with utter failure.

- The only possible exception is the one cancer vaccine that's FDA-approved: sipuleucel T in prostate cancer. I don't have high-level statistics on usage, but general opinion is somewhere between "it literally does nothing" and "it is of modest use in a pretty select group of patients." In my experience it is rarely used.