Tampa, FL—A study seeking to determine if the immune response to the mRNA-1273 Moderna vaccine differs among patients with solid tumors and hematologic cancer came up with highly variable results.

A report in the Journal of the American Medical Association Oncology noted that in a cohort study of 515 patients with cancer, seropositivity after the first and second COVID-19 vaccine doses was 71% and 90%, respectively. It added that antibody levels after vaccination were substantially higher among patients who were seropositive prior to vaccination.

Response to the vaccine differed by cancer diagnosis and treatment received, according to the study conducted at Moffitt Cancer Center in Tampa. "These findings suggest that patients with hematologic cancer and those who are receiving immunosuppressive treatments may need additional vaccination doses," the authors advised.

Researchers wrote that they conducted the study because cancer patients have high rates of morbidity and mortality after SARS-CoV-2 infection, yet immune response to mRNA-1273 vaccination across multiple cancer types and treatments has not really been determined.

Included in the study were 515 adults with cancer who received their first mRNA-1273 dose between January 12, 2021, and January 25, 2021, and who agreed to blood tests before and after vaccination. Participants had a mean age of 64.5 (11.4) years, and 50.9% were women; 93% were white.

Results indicated that seropositivity after vaccine dose 2 was 90.3% (465; 95% CI, 87.4%-92.7%) among patients with cancer. That rate was substantially lower among patients with hematologic cancer (84.7% [255]; 95% CI, 80.1%-88.6%) versus solid tumors (98.1% [210]; 95% CI, 95.3%-99.5%), and was lowest among patients with lymphoid cancer (70.0% [77]; 95% CI, 60.5%-78.4%).

In addition, researchers advised that patients receiving a vaccination within 6 months after anti-CD20 monoclonal antibody treatment had a significantly lower seroconversion (6.3% [1]; 95% CI, .2%-30.2%) compared with those treated 6 to 24 months earlier (53.3% [8]; 95% CI, 26.6%-78.7%) or those who never received anti-CD20 treatment (94.2% [456]; 95% CI, 91.7%-96.1%).

Overall, they reported, low antibody levels after vaccination were observed among patients treated with anti-CD20 within 6 months before vaccination (GM, 15.5 AU/mL; 95% CI, 9.8-24.5 AU/mL), patients treated with small molecules (GM, 646.7 AU/mL; 95% CI, 441.9-946.5 AU/mL), and patients with low lymphocyte (GM, 547.4 AU/mL; 95% CI, 375.5-797.7 AU/mL) and IgG (GM, 494.7 AU/mL; 95% CI, 304.9-802.7 AU/mL) levels.

"Noteworthy was the complete lack of an antibody response in patients treated with anti-CD20 monoclonal antibodies and low seroconversion percentages among those treated with BTK inhibitors, venetoclax, and CD19-CAR-T," the authors wrote. "After the second dose, antibody levels were higher among patients who were seropositive at baseline compared with those who were seronegative. After 2 vaccine doses, patients who had a seropositive status before vaccination achieved antibody levels similar to those of adults without cancer, suggesting that patients with cancer with initially poor immune responses may benefit from additional vaccine doses, including a third dose, as recently recommended."

Researchers explained that because of B-cell defects, hematologic cancer is associated with lower rates of antibody response to vaccines, even without anticancer therapy. They added that seroconversion percentages among patients with allogeneic hematopoietic stem cell transplant were high.

"Patients receiving CD19-CAR-T had low seroconversion percentages, though most received CAR-T more than 1 year before the study, were in remission, and had not received cancer treatment in the past year, suggesting prolonged immunosuppression after CD19-CAR-T therapy," according to the study.

"Antibody levels required to confer protection against SARS CoV-2 are unknown," the authors pointed out. "However, lower initial antibody levels are of concern because levels decline over time; higher levels are needed to neutralize variants of concern, and new variants continue to emerge. Patients who had seropositive status before the start of vaccination had antibody levels similar to levels after 1 vaccine dose and substantially higher levels after 2 doses than patients with initially seronegative status. It remains to be tested whether a third dose will overcome the poor vaccine response among patients who did not seroconvert or had very low antibody levels."

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