Determination of SARS-CoV-2 IgG antibody levels in hematology-oncology patients after COVID-19 vaccination

OBJECTIVE: Cancer patients are among the high -risk groups where COVID-19 infection tends to be severe and can lead to increased mortality. Therefore, they are included in the priority groups for COVID-19 vaccination. This study aimed to compare the levels of SARS-CoV-2 immunoglobulin G (IgG) antibodies following two different COVID-19 vaccinations between hematology -oncology patients and healthcare personnel and to identify factors associated with these antibody levels. PATIENTS AND METHODS: A prospective study was conducted with 91 hematology -oncology patients (cancer group) and 75 healthcare personnel (control group) from January 2020 to June 2023. The cancer and control groups comprised adults who had received a booster dose, with either a single dose of BNT162b2 or two doses of CoronaVac"' spaced one month apart, following their primary vaccination with two doses of either CoronaVac"' or BNT162b2. Four weeks after the administration of the booster dose, levels of SARS-CoV-2 IgG antibodies were assessed using an ELISA kit. Antibody levels above 50 AU/mL were accepted as signifying seropositivity. RESULTS: The median SARS-CoV-2 IgG antibody level was lower in the cancer group compared to the control group (4,509 vs. 7,268, p = 0.004), while the rate of seroconversion was similar between the groups (97.8% vs. 100%, p = 0.564). In the cancer group, no association was found between SARS-CoV-2 IgG antibody levels and age, sex, comorbidity, type of malignancy, stage and duration, or type of vaccine. CONCLUSIONS: In cancer patients, the seroconversion positivity rate was about 98%. However, antibody responses were still lower compared to the control group. No difference was detected in antibody levels among cancer patients based on the type of vaccine.