Public health officials and physicians have stressed the importance of COVID-19 vaccination, especially among immunocompromised patients. This population, which includes those with cancer, remains at high risk for infection. Although this group was one of the first to receive the vaccine when it became available in late 2020, at the time it was unclear whether the shot would help patients develop antibodies to help prevent infection or lessen the risk of severe illness.

To help answer that question, Moffitt Cancer Center researchers quickly coordinated one of the largest observational studies following 515 cancer patients to determine if they had an immune response to the Moderna vaccine and if that response differed by diagnosis and treatment. Participants provided blood samples before their first and second doses of the vaccine and again one month later. Each sample was tested for COVID-19 antibodies. For comparison, antibody levels were measured for 18 healthy adults receiving the Moderna vaccine.

The results, published in JAMA Oncology, showed that most cancer patients had developed antibodies after receiving the vaccine. Overall, 71.3% of patients developed antibodies after the first dose, 90.3% after the second. There were, however, differences among cancer types. Patients with blood cancers had lower antibody rates when compared to those with solid tumors, 84.7% versus 98.1%.

“Although we did see solid tumor patients develop antibodies at a higher rate, it is important to point out the antibody titers were lower than seen in healthy adults. Unfortunately, we don’t know how much antibody a person needs to provide full protection against the virus,” said Dr. Anna R. Giuliano, founding director of the Center for Immunization and Infection Research in Cancer at Moffitt.

Blood cancer patients with lymphoid disease, such as chronic lymphocytic leukemia and B-cell non-Hodgkin lymphoma, had the lowest rates of developing antibodies. And patients with those diseases who were on active treatment fared even worse.

“This finding was to be expected. Lymphoid disease affects B cells, which your immune system needs to make antibodies. If a patient’s B cells are suppressed, either through the disease process itself or treatment, chances are low they would be able to make antibodies,” said Dr. Jeffrey Lancet, chair of the Malignant Hematology Department at Moffitt. 

The researchers are continuing to follow study participants, taking blood samples at six, 12 and 24 months. The team has also launched a companion study evaluating immune response in cancer patients after a third dose of the Moderna vaccine.