That question—whether the vaccine would protect transplant patients like Keefer and others with compromised immune systems—set Dorry Segev, director of the Epidemiology Research Group in Organ Transplantation at Johns Hopkins, onto a path of scientific inquiry that has produced more than three dozen papers since February on COVID-19 vaccination in immunocompromised people and resulted in a $40 million grant from the National Institutes of Health to study the effectiveness of giving kidney transplant recipients a third vaccine dose. The first part of the COVID-19 Protection After Transplant study also aims to learn which transplant patients can benefit from a third dose and which ones may need to take a different approach, such as temporarily reducing their transplant medication dosage before vaccination.