So we also have artificial and natural. Now, artificial includes actually taking those antibodies, injecting those antibodies into our body and allowing those antibodies to circulate our system. Now, the problem with this is it doesn't produce any memory cells. And so after several months, we essentially lose any immunity that we initially had as a result of that passive immunity. And we also have the natural process of passive immunity as we discussed just a moment ago. So antibodies transferred via the placenta when the woman is essentially pregnant or during the process of breastfeeding when the milk is transferred to that child along with those immunoglobulin, specifically immunoglobulin A.