The human immune system has a more effective response to an invader during a second exposure than during the first exposure.

Question

Quizplus · Accepted Answer

This is because during the first exposure, the immune system has not yet encountered the invader and needs to mount a response from scratch. But during a second exposure, the immune system remembers the invader and can mount a faster and more effective response thanks to memory cells that were generated during the first exposure.

The Human Immune System Has a More Effective Response to an Invader