Normally, typing /effect @p jump_boost 1000000 255 will negate (or at least reduce a lot) of fall damage, without affecting how high the player jumps. I believe this is an intended feature. However, when taking damage, the player is able to jump very high.

I was expecting the player to jump only one block. Instead, the player was able to jump very high if they were taking damage (possibly midair).

Steps to reproduce:
1. Type /effect @p poison 1000000 100
2. Type /effect @p jump_boost 1000000 255
3. Hold space bar

It might be helpful to know that I was mapmaking when this issue was discovered.