Up to one-third of patients with immune-mediated inflammatory diseases taking methotrexate failed to achieve an adequate humoral or cellular immune response to Pfizer’s mRNA COVID-19 vaccine in a small observational study.

Doctors analysed the immune response after a second dose of the vaccine in 82 patients with autoimmune or immune-modulated diseases in two cohorts — one at NYU Langone Health, New York, US and one in Erlangan, Germany.

The findings in the patients (who mainly had rheumatoid arthritis, psoriasis or psoriatic arthritis) were compared with those for 208 healthy controls.

Overall, the mean age of participants not on methotrexate and controls was about 49, while the mean age of those taking methotrexate was 63. About 66% of participants were women and 61%-77% were White.