In a U.S. and Swiss study, nearly all patients with cancer developed an immune response to COVID-19 mRNA vaccines 3 to 4 weeks after receiving their second dose. However, a small group of the patients exhibited no response, raising questions about how their protection against the virus will be addressed moving forward. These findings were published by Addeo et al in Cancer Cell.

Among the 131 patients studied, 94% developed antibodies to the coronavirus, but 7 high-risk patients did not.

“We could not find any antibodies against the virus in those patients,” said co-senior study author Dimpy P. Shah, MD, PhD, of the Mays Cancer Center at UT Health San Antonio MD Anderson. “That has implications for the future. Should we provide a third dose of vaccine after cancer therapy has completed in certain high-risk patients?”

“With other vaccines and infections, patients with cancer have been shown not to develop as robust an immune response as the general population,” said co-senior study author Ruben Mesa, MD, FACP, Executive Director of the Mays Cancer Center. “It made sense, therefore, to hypothesize that certain high-risk groups of patients do not have antibody response to COVID-19 vaccine.”

“Patients with hematologic malignancies, such as myeloma and Hodgkin lymphoma, were less likely to respond to vaccination than those with solid tumors,” added Pankil K. Shah, MD, PhD, of the Mays Cancer Center, who served as co-lead author of the study with Alfredo Addeo, MD, senior oncologist at the Geneva University Hospital.

Further Findings

In the high-risk groups, patients receiving the monoclonal antibody rituximab within 6 months of vaccination developed no antibodies. Patients on cytotoxic chemotherapy developed antibody response, but it was muted compared to the general population. “How that relates to protection against COVID-19, we don’t know yet,” Dr. Dimpy Shah said.

The Delta variant and other mutants of the COVID-19 virus were not examined in the study. The team also did not analyze the response of infection-fighting T cells and B cells in the patients with cancer.

The median age of patients in the study was 63 years. Most of the patients (n = 106) had solid cancers; however, there was a smaller population with hematologic malignancies (n = 25). The study population was 80% non-Hispanic White, 18% Hispanic, and 2% Black.

“We recommend that future studies be done in Black, Asian, and Hispanic patients, as well, to see if there are any differences in vaccination immune response,” said Dr. Mesa.

In countries where there is lack of availability of vaccination, it has been hypothesized that one dose might confer adequate protection, but this may not be true in the case of patients with cancer, Dr. Dimpy Shah said. “We observed a significant difference in response when two doses were given. At least for patients with cancer, two doses are very important for robust antibody response.”

Dr. Pankil Shah said the study is unique because, unlike a few studies conducted in the past that evaluated immune response on the day of the second dose or within 7 days of it, this study waited 3 to 4 weeks to obtain results.

Patients with high-risk cancers, especially those receiving anti-CD20 antibodies, should continue to take precautions even after being vaccinated, the study implies. “They still need to have that awareness that they could potentially be at risk because their body has not responded to vaccination,” Dr. Pankil Shah said.

Disclosure: This research was supported by the National Cancer Institute, the American Cancer Society, and the Hope Foundation for Cancer Research. For full disclosures of the study authors, visit cell.com/cancer-cell.