Effectiveness and immunogenicity of SARS-CoV-2 booster vaccine in immunosuppressed systemic autoimmune disease patients: A prospective study

Introduction and objectives

Patients with systemic autoimmune rheumatic disease (SARD) are a vulnerable population for severe COVID-19 and worse response to vaccination, prompting the need of a booster vaccine. Data regarding its response is limited and inconsistent. The aim of this study was to assess the effectiveness and immunogenicity of the third dose of the SARS-CoV-2 vaccine in immunosuppressed SARD patients.

Materials and methods

We conducted a prospective study in immunosuppressed SARD Portuguese patients, who received a SARS-CoV-2 booster vaccine, from October 2021 to August 2022. We evaluated COVID-19 incidence in the following 6 months, as well as vaccine immunogenicity through anti-Spike IgG titers and T-cell reactivity to the Spike protein.

Results

We included 131 patients with a mean age of 54.9 ± 12.2 years. Almost 40% (n = 52) developed COVID-19 within 6 months after the booster, but 51 (98.1%) were mild infections. Median post-booster antibody levels and antibody variation were 9540.7 (14,724) and 8937.9 (11,561.3) AU/mL, respectively, and 73.3% (n = 96) of the patients showed post-booster T-cell reactivity. Antibody variation was significantly lower in the COVID group (p = 0.015). Although post-booster antibody levels and T-cell reactivity were statistically significantly lower in the patients under biologic DMARD, there was not a significant increase in COVID-19 incidence.

Conclusions

This study shows that a booster vaccine elicits strong immunogenicity and reduces COVID-19 severity, highlighting its importance in immunosuppressed SARD patients. Larger and more homogeneous cohorts are needed to guide periodic booster administration in this susceptible population.