Until recently, if someone wanted to donate a kidney to a family member or a friend, the recipient would receive the kidney at the time of the donation, or very close to this time. This timing restriction created a problem for Howard Broadman, a retired California judge. Judge Broadman wanted to donate a kidney to his grandson, who, however, did not need the kidney yet, but was likely to need one in 10 to 15 years, at a time when Broadman might be too old to donate. Judge Broadman approached UCLA and proposed to donate the kidney for a promise (a voucher) that his grandson will have priority to receive a kidney when he needs one.

A system of kidney vouchers that builds on Judge Broadman’s case was subsequently developed by Professor Marek Pycia and other members of an interdisciplinary team including Jeffrey Veal from UCLA David Geffen School of Medicine, other UCLA, USC, and Cornell medical practitioners, and Alexander Capron from USC Law. This system— described in their recent paper “Vouchers for Future Kidney Transplants to Overcome ‘Chronological Incompatibility’ Between Living Donors and Recipients”—is already being used to organize promises of priority for future kidney transplants.

Kidney vouchers need to be legal: for instance, in the US it is illegal to trade a kidney for money or other valuable consideration, and for this reason each kidney voucher is issued in the name of a particular recipient and cannot be used by anyone else. The system also needs to be sustainable: it needs to ensure that the hospitals in the system are able to offer kidneys to voucher holders, when they need transplants and come to redeem their vouchers.

Sustainability is where economics enters the picture. The voucher system resembles a retirement system such as US Social Security. Each time a kidney voucher is issued, one more kidney can be transplanted to someone waiting for it. Later, however, when the voucher is redeemed, a kidney is needed for the voucher holder. The system is sustainable provided the number of donations into the voucher system stays constant or is growing.

Each new voucher allows the participating hospitals to initiate a chain of transplantations, in which a first patient receives the kidney donated for a voucher, a second patient receives the first patient’s donor’s kidney, etc. This chain provides an opportunity to honor a previously issued voucher by transplanting the last kidney in the chain to a patient redeeming the voucher. At the same time, the chain enables several patients with incompatible donors to receive a kidney, and thus not only patients with vouchers benefit but also an average patient without a voucher faces a shorter wait time.

The system, started recently at UCLA, is quickly gaining popularity. By now, over twenty leading US transplant centers joined it, and, in addition to Judge Broadman, over ten donors donated kidneys to give vouchers to their close ones and protect them against the consequences of anticipated kidney failure.

The paper, ahead of print at Transplantation, is available electronically, and kidney vouchers were featured in the Boston Globe, CBS, Fox News, Reuters, USA Today, Wall Street Journal, and many other outlets.