Effect of MTX Discontinuation on Shingrix Response in RA

The goal of this clinical trial is to learn if methotrexate discontinuation affect on immunogeneity of shingrix in RA patients. The main questions it aims to answer are: Discontinuation of methotrexate after shingrix immunization increase efficacy of the vaccine in patients with RA ? Researchers will compare humoral and cell-mediated immunity against herpes zoster in RA patients who are vaccinated by shingrix, and compare these immunity between RA patients with MTX discontinuation and MTX continuation groups. Participants will: Vaccinated with shingrix twice. MTX continuation group will keep taking MTX after shingrix vaccination, whereas MTX discontinuation group will stop MTX for 2 weeks after shingrix vaccination. Visit the clinic at baseline (first shingrix vaccination), 2 months later for 2nd shingrix vaccination, then 3 \& 6 months later from baseline to achieve blood sample.