Antibody responses to COVID-19 vaccines may persist at 6 months for cancer patients on active treatment and those who have received a stem cell transplant (SCT), according to research published in JAMA Oncology.

Researchers observed persistent anti-SARS-CoV-2 spike protein receptor binding domain (anti-RBD) antibodies at 6 months after the second dose of an mRNA COVID-19 vaccine. 

The study also showed a 20-fold increase in anti-RBD antibodies after the third vaccine dose. 


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The study included 453 patients, 70% with solid tumors and 30% with hematologic malignancies. Patients had received an SCT (25%) or they were receiving chemotherapy (41%), immunotherapy (16%), a targeted oral agent (14%), or chemoimmunotherapy (5%). 

The patients’ mean age was 60.4 years, and 56% were women. Most patients received the Pfizer-BioNTech vaccine (61%), followed by the Moderna vaccine (36%), and the Janssen/Johnson & Johnson vaccine (4%). 

The researchers evaluated anti-RBD and neutralizing antibody responses to COVID-19 vaccines over time. Specifically, the team assessed geometric mean titers (GMTs) of the anti-RBD, the percentage of neutralization of anti-RBD antibodies, and the correlation between anti-RBD and neutralizing antibody responses.

Before vaccination, the patients’ GMT of anti-RBD antibodies was 1.7. At 14 days after the first vaccine dose, the GMT increased to 18.65. 

At 1 month after the second dose (or 2 months after the Johnson & Johnson vaccine), the GMT of anti-RBD antibodies was 470.38. The GMT decreased to 425.80 at 3 months after the second dose (4 months after J&J). 

The GMT increased to 447.23 at 6 months after the second dose (7 months for J&J) and to 9224.85 at 1 month after the third dose.

The researchers found that men, patients older than 65 years of age, and patients with hematologic malignancies were more likely to have lower anti-RBD GMTs at 3 months after the second vaccine dose.

The researchers observed a strong correlation between anti-RBD titers and neutralization (Spearman correlation coefficient, 0.93; P <.001).

The rate of threshold neutralization (at least 30%) was observed in 39% of patients analyzed at 14 days after the first vaccine dose (56/144), 80% of patients analyzed at 1 month after the second dose (203/252), and 81% of patients analyzed at 3 months after the second dose (135/166). 

“The results of our cross-sectional study show that approximately 80% of the patients remained above the threshold of an anti-RBD level of 100 U/mL or higher at 6 months,” the researchers wrote. “Although more data are needed to confirm this level as protective, if established, anti-RBD can potentially be used to prioritize additional vaccine doses, especially in regions of the world with limited vaccine resources.” 

Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures. 

Reference

Khan QJ, Bivona CR, Martin GA, et al. Evaluation of the durability of the immune humoral response to COVID-19 vaccines in patients with cancer undergoing treatment or who received a stem cell transplant. JAMA Oncol. Published online April 21, 2022. doi:10.1001/jamaoncol.2022.0752