Adequate Immunogenicity And Low Rate of Severe Adverse Events After SARS-CoV-2 mRNA-Based Vaccination In Patients With Solid Malignancies On Active Treatment Starts To Decline 3 Months After Complete Primary Course of Vaccination

Abstract

Background: SARS-CoV-2 vaccination in cancer patients is crucial since they are at increased risk of severe COVID-19 disease course, but data on efficacy and safety of vaccination are scarce.Methods: We performed a prospective observational study of patients with solid cancers on active anticancer treatment (chemotherapy, immunotherapy with immune checkpoint inhibitors (ICI) or targeted therapy) that received mRNA-based SARS-CoV-2 vaccination at two institutions in Slovenia. The immunogenicity was assessed by the detection of anti-SARS-CoV-2 S1 IgG antibodies in serum; patients were sampled before, 2-3 weeks after the first dose, 2-3 weeks after the second dose, and 3 months after the complete primary course of vaccination. The results were also compared to controls, sampled at similar time points.Results: Between March and July 2021 112 patients were included in the analysis. The seroconversion rate in patients without prior COVID-19 infection was 96% after the complete primary course of vaccination with 2 doses, compared to 100% for healthy controls. The seroconversion rate after vaccination for patients on chemotherapy, ICI, and targeted therapy was 100%, 91%, and 97%, respectively. All controls and the majority of patients on chemotherapy and targeted therapy, but only 83% for patients on ICI were adequate responders (anti-SARS-CoV-2 S1 IgG ≥ 880 ng/ml). Three months after the vaccination, a significant drop in antibody levels was observed in patients receiving ICI compared to controls (P < 0.001). Adverse events were mostly mild and predictable, none of the patients experienced serious adverse events after vaccination.Conclusions: Immunogenicity after mRNA-based vaccination against SARS-CoV-2 in cancer patients is only slightly impaired, but influenced by the type of anticancer therapy received. Patients on ICI have the slightest and gradual antibody production. Since antibody levels decline after three months, a third vaccination dose is reasonable to provide adequate protection against severe COVID-19 disease course.The study was approved by the National Ethics Committee (No. 0120-39/2021/6)