Assessing Immune Response to 3^rd Dose of COVID-19 Vaccine Series in Patients Undergoing Cancer Treatment at University Medical Center- New Orleans

Background: COVID-19 pandemic remains a global emergencies. Vaccines against the virus SARS-CoV-2 have been shown to reduce incidence and severe complications from COVID-19 infection. Previous studies have shown that patients receiving active cancer therapies for solid or hematological malignancies demonstrated a significantly lower response after initial 2- doses of vaccines, in comparison to the general population. There is limited data on the immune response to a 3^rd dose of the mRNA COVID-19 vaccine in patients receiving active treatment for malignancies and especially in minorities. This study aims to assess immune response against SARS-CoV-2 after 3^rd dose of mRNA vaccination in this particular population.

Study Design: Between September 2021 and January 2022, 119 patients on active cancer treatments at University Medical Center- New Orleans were enrolled on this prospective study (IRB Protocol 641). Plasma samples were collected before and approximately 3-6 weeks after the 3^rd vaccine dose. 40 patients received the 3^rd vaccine dose and completed the study. Serum antibody testing by ELISA was performed. IgG response was assessed by testing for antibodies against the wild type SARS-CoV-2 proteins RBD and N (natural COVID-19 infection).

Results: Patient demographics consisted of 66.4% African American, 27.3% Caucasian, and 6.4% others. On the average, there was an approximately 8x fold increase in titer response after the 3^rd dose of SAR-CoV-2 vaccination. Titer response was highest in patients on immunotherapy compared to those on cytotoxic chemotherapy. Higher titer response were also observed in patients with metastatic cancers compared to non-metastatic cancers, in African Americans compared to other ethnicities, and males. Patients who received the 3^rd vaccine dose six months after initial 2-dose series tended to mount higher titer response compared to those who received their 3^rd dose within 3 months. None of study subjects were hospitalized for COVID-19 infection during the duration of this study.

Conclusion: 3^rd dose mRNA vaccines against SAR-CoV-2 were effective in preventing infections and complications from COVID-19 infection in patients and ethnic minorities who are on active treatment for solid and liquid malignancies. Our study is limited by the small number of subjects. Studies are being conducted to evaluate duration of antibodies response in this patient group compared to general population.

No relevant conflicts of interest to declare.