I wondered what you were asking, so I took a little time to look at Lev 15.
First, I would like to say that Jesus did not change the law, he fulfilled it. In short, he sacrificed himself so that you would not be bound to the Law for your Salvation. You have to realize that
much of the Law was addressed to a huge group of people in exile.
The people were not in exile when the law was given, they were in deliverance.
It was much like a refugee camp. God used it to keep his people safe.
The law was not given for health purposes, it was given for holiness purposes.
Now with that in mind 15:22 addresses an issue that involved blood. Shed blood is a means of transmitting disease.
God used 15:22 to prevent the transmission of diseases.
The law was not given for health purposes, and Lev 15:22 is not about transmission of diseases.
The whole chapter is about bodily discharges,
all bodily discharges were
defiling--semen, spit, menstrual blood, diarrhea, urethral--not just menstrual blood.
Just about all of Leviticus is symbolic or a pre-figure.
God didn't give animal sacrifice because he hated animals.
It was a symbol or prefigure of Christ's sacrifice.
And God didn't give the defilement laws of Lev 15 for health reasons.
They were a symbolic picture of the corruption of man (Ro 3:9-11),
where everything which proceeds from unregenerate man is defiled.
They were to teach the meaning of moral defilement as spiritual uncleanness,
which separates from God, and must be cleansed.