Humoral Response of Different Types of SARS-CoV-2 Vaccines in Patients with Autoimmune Rheumatic Diseases: Experiences from a Serbian Cohort.

Background: Data are scarce on the immunogenicity of coronavirus disease 2019 vaccines in patients with autoimmune rheumatic diseases (ARD).

Objectives: To measure the immunoglobulin G (IgG) response after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunization and to evaluate clinical characteristics associated with seropositivity.

Methods: Samples were collected after the second and third doses of the three different types of vaccines in ARD patients. Seroconversion rates and IgG antibody S1/S2 titers were measured.

Results: The type of ARD diagnosis and previous treatment had no significant impact on the serum IgG antibody levels measured after the second (P = 0.489 and P = 0.330, respectively) and boost dose (P = 0.441 and P = 0.446, respectively). What made a significant difference regarding serum IgG antibody levels after the second dose was the type of SARS-CoV-2 vaccine. The difference was highly statistically significant for all vaccine types (P = 0.001 with the highest odds ratio for the mRNA vaccine). After the boost with the mRNA vaccine, all patients achieved a high level of serum IgG antibody levels (t = 10.31, P = 0.001). No ARD patients experienced serious post-vaccinal reactions. Eight patients developed COVID-19 before the boost dose.

Conclusions: In ARDs patients, the highest level of serum IgG antibody against S1/S2 proteins was achieved with the mRNA vaccine, irrespective of the therapy applied or the type of the disease. We recommend a booster dose with mRNA vaccine in all ARDs for the highest SARS-CoV-2 protection without serious post-vaccinal reactions observed.