And in many cases, receiving a vaccine essentially creates no effects whatsoever no effects that we can actually visibly see or physically feel. Now, to further prevent us from actually experiencing any form of discomfort during vaccination what medical researchers do is they essentially kill off that pathogen altogether and they only take a very small portion of an antigen of that pathogen. So they essentially cut that pathogen and use only the epitote, the antigenic determinant of that antigen because it's that part of the antigen that ultimately binds to the antibodies of our body. And in this way, the body can still produce antibodies following vaccination and at the same time, it will create a very, very little effect that will actually hurt the body. Now, everything we discussed so far is active immunity. And active immunity involves developing our memory cells.