China has been harvesting organs from prisoners, including prisoners of conscience (those jailed for nothing more than practicing a religion that is not state-sponsored), for years, and despite saying they have reformed the practice in 2015, China is still doing it, according to human rights workers David Matas and Ethan Gutmann.
According to the lawyer and investigator, China "obviously has got a lot of people sitting around waiting to be killed for a transplant, and they're just picking the right person to be killed depending on who the patient is."
Chinese businesses profit from transplant tourism -- people coming from other countries to get quick organ transplants -- as well as meeting local needs. There aren't enough organs volunteered to meet demand, so China takes them from prisoners. Prison officials coordinate with doctors in China to make this happen.
According to authorities around the world who keep track of people going to China for transplants, the numbers have markedly reduced, indicating that China has made serious efforts, but it has not stopped.
China executes thousands of people per year -- around 3 times the amount of the rest of the world combined, although stats are hard to get because China blocks publication of them (it's currently a state crime), even though Amnesty International and other groups keep track of all executions in all countries.
Many of those executed come from populations China doesn't like very much, like religious and ethnic minorities in Tibet and Xinjiang.