When the last round of chemo is given to "destroy your immune system" doesn't it take like 2 weeks to see any signs of immune cells? I knew someone who passed a

When the last round of chemo is given to "destroy your immune system" doesn't it take like 2 weeks to see any signs of immune cells? I knew someone who passed away from leukemia last year because the various infections they contracted in that 2 week window caused irreparable lung damage.