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. And we said we can gain active immunity either artificially or either via natural means when infection actually takes place. Now, let's discuss something called passive immunity. Passive immunity basically means we do not develop any memory B cells or memory T cells.