06/01/2026
A stem cell transplant saved Amelia Sullivan's life, but it also wiped out the immune system and childhood vaccinations she had built up over two decades
As her body recovered after treatment for Hodgkin lymphoma, flu season became especially difficult, with even minor illnesses feeling severe, she tells PEOPLE
Now back to restarting her vaccines, Sullivan sees the process as another milestone in her cancer journey.
Amelia Sullivan was 20 years old when what was believed to be heart and lung problems turned into a cancer diagnosis.
In August 2023, doctors discovered that her months of chest pain, shortness of breath and an elevated heart rate were actually caused by tumors pressing against her trachea, heart and arteries, leading to a stage 2 Hodgkin lymphoma diagnosis.
After six months of chemotherapy, the Colorado native entered remission in March 2024, only to relapse later that year and begin another grueling round of treatment that ultimately led to a stem cell transplant on March 10, 2025.
According to the Cleveland Clinic, a stem cell transplant can treat — and sometimes cure — certain blood disorders, cancers and autoimmune diseases by replacing unhealthy stem cells with healthy ones, either from the patient's own bone marrow or donated stem cells from another person.
What followed was not just recovery from cancer, but the rebuilding of an immune system erased by the very treatment that saved her life, Sullivan tells PEOPLE.
Before the transplant, Sullivan underwent high-intensity chemotherapy designed to wipe out the cancer completely. But the treatment also destroyed the healthy stem cells responsible for her immune system, erasing the immunological memory of past vaccines and infections.
"Because it's not possible to just get rid of bad cells, to eliminate the cancer, they had to eliminate my healthy stem cells,” she explains. “Which, in essence, erased my entire immune system, including all of the vaccinations and immunities that I got when I was a child and developed over 21 years of life," she shares.
Doctors harvested Sullivan's stem cells before treatment and later transfused them back into her body to rebuild her immune system. During recovery, she developed engraftment syndrome, an inflammatory reaction that can happen when new stem cells begin growing after a transplant, and Sullivan was moved to the ICU and placed on life support.
Looking back, she says, “It's ironic that what eventually saved my life almost killed me first.”