We will – prospectively – include RA patients who develop herpes zoster, while being treated with biologics (anti-TNF, tocilizumab, rituximab, abatacept) and a control group comprised of patients with herpes zoster [RA patients under non-biologic therapies (corticosteroids/csDMARDs) and age- and sex-matched healthy controls). The gene discussed is TNF; the disease is rheumatoid arthritis.