The main giveaway that it's designed to produce an immune response would be the presence of an immunological-adjuvant:
a substance that increases or modulates the immune response to a vaccine.
Now, of course, adjuvants are used in cancer treatment, but the difference with inoculations for pathogens is that there'd be an additional molecule or set of them which triggers a specific immune response.
There are nearly a dozen types of "vaccine" for COVID and variants, the majority are focusing on making use of the spike protein of the virus to create a response, but there are some which are designed to create a response to the capsid proteins, i.e. the viral-shell. Neither the spike protein nor the capsid would be expected to be found natively existing in the human body.
This doesn't mean they all contain the spike protein (or any other target protein), the mRNA version for example is designed to induce the body's own systems to produce the spike.
Some contain an adenovirus - a familiar companion found usually in the mucus membranes of human populations causing a number of familiar respiratory diseases. This being also designed to induce the body to produce the spike protein and only that. They would be otherwise reproductively inert.
Some contain artificially produced virus-like particles which have some characteristic in common with the target virus.
The one producing arguably the broadest response would be the virus particles themselves, artificially cultured then inactivated before administration. This would be straight-up identify the virus that the vaccine is designed to combat. At the time of writing, these seem to have been primarily developed and deployed in China.