The CONQUER study team followed 800 immunized individuals (healthy, cancer patients, kidney transplant recipients), conducting serological tests from the first to the sixth COVID-19 vaccine doses. We successfully correlated immune responses induced by immunization to subsequent breakthrough infections. Four research articles were published, each contributing valuable insights to optimize vaccination strategies, ensuring adequte access to tailored immunization strategy for vulnerable patient populations. In addition, there is poor reproducibility among common commercial serological assays quantitatively, semi-quantitatively, and qualitatively. To address this, we are actively engaging with manufacturers of serological methods to enhance their reproducibility. The availability of well-characterized and standardized assays for assessing humoral and cellular immune responses in Ontario is critical in our collective efforts to evaluate the effectiveness of SARS-CoV-2 immunization.

Objectives:

Post COVID-19 immunization, in healthy, cancer and renal transplant cohorts, assess their immune responses with correlation to subsequent breakthrough infections.

Methodology:

In 800 immunized healthy individuals, cancer patients, and kidney transplant patients, serological tests were performed post the first to the sixth doses of immunization.

Results/outcomes:

1. In healthy participants, 37.2% of triple-vaccinated, 19.0% of double-vaccinated individuals, and 1.5% of individuals with a single dose have SARS-CoV-2 antibody responses higher than the average antibody concentration prior to known breakthrough cases.
2. In cancer cohort, we demonstrated that 29.5% of triple-vaccinated cancer patients had SARS-CoV-2 antibody responses higher than the average antibody concentration prior to known breakthrough cases.
3. Even with four doses of immunization, a significant number of renal transplant participants (32.4%) were not seroconverted, and a significant number of participants (83.8%) had SARS-CoV-2 antibody responses lower than the average antibody concentration prior to the known breakthrough infections.
4. A poor correlation exists between common commercial assays, quantitatively, semi-quantitatively, and qualitatively.
5. Our unpublished data (manuscript in preparation) suggested that T cell function is an integral component of immunity derived from SARS-CoV-2 immunization. This will fill the knowledge gap and provide insights of cellular immune responses in protective immunity against future infection.

Next steps:

The infrastructure we successfully built, including research participants with comprehensive serological data spanning from the initial to the sixth dose of SARS-CoV-2 vaccination, forms a solid foundation for ongoing research endeavors.. This will inform vaccination strategies and effectively address many unknowns in post-pandemic public health policy.

Four research articles (SEAMO was acknowledged as the funding agency in 3 articles) were published, in which Dr. Gong was the senior corresponding author.

1. Chan A, Martinez-Cajas J, Yip PM, Kulasingam V, Garland J, Holland D, Khaled Shamseddin M, Gong Y. *. Evaluation and Comparison of Four Quantitative SARS-CoV-2 Serological Assays in COVID-19 Patients and Immunized Healthy Individuals, Cancer Patients, and Patients with Immunosuppressive Therapy. Clinical Biochemistry 116 (2023) 1–6. DOI: 10.1016/j.clinbiochem.2023.02.010
2. Macrae K, Martinez-Cajas J, Bessai K, Abdulhamed A, Gong Y*. Quantitative Analysis of SARS-CoV-2 Antibody Levels in Cancer Patients Post Three Doses of Immunization and Prior to Breakthrough COVID-19 Infections. Current Oncology. 2022; 29(10):7059-7071. https://doi.org/10.3390/curroncol29100554
3. Macrae K, Gong CY, Sheth P, Martinez-Cajas J, Gong Y*. Quantitative Analysis of SARS-CoV-2 Serological Responses Post Three Doses of Immunization and Prior to Breakthrough COVID-19 Infections. Vaccines. 2022; 10(10):1590. https://doi.org/10.3390/vaccines10101590
4. Robinson R, Mazurek A, Xu M, and Gong Y*. Quantitative Analysis of SARS-CoV-2 Antibody Status between Patients with Cancer and Healthy Individuals with Extended Vaccination Dosing Intervals in Canada. Curr. Oncol. 2022, 29(1), 68-76; https://doi.org/10.3390/curroncol29010006