Humoral Response to SARS-CoV-2 Vaccine of a Patient Receiving Methotrexate Treatment and Implications for the Need of Monitoring

We report a case of monitoring the antibody response to the BioNTech–Pfizer vaccine of a 50-year-old female diagnosed with rheumatoid arthritis undergoing treatment with methotrexate (MTX). Antibody levels were measured 21 days after dose 1 (i.e., on the day of dose 2) and then 8, 14 and 30 days after dose 2 with Elecsys Anti-SARS-CoV-2 S assay (Roche Diagnostics). Patient showed a negative result after dose 1 and had the serum sample retested using a LIAISON(®) SARS-CoV-2 TrimericS IgG assay (DiaSorin), which showed a positive result. Subsequent samples were tested using both assays. Antibody levels kept increasing but at a much slower rate than in patients not receiving any immunomodulatory therapies. Other research indicates that among patients with autoimmune diseases, those receiving disease-modifying antirheumatic drugs (DMARDs) have higher COVID-19 mortality than those treated with tumor necrosis factor inhibitors (TNFis). These results indicate the need for people with autoimmune diseases to be carefully observed following vaccinations, including testing of antibody levels, and treated as potentially at risk until the effect of vaccination is confirmed. The different available vaccines should also be tested to verify their usefulness in the case of people with autoimmune diseases and those who take different immunomodulatory medications.