People who received two doses of the Pfizer COVID-19 vaccine while on TNF inhibitors — a class of immunosuppressants used to treat rheumatoid arthritis and other autoimmune conditions — generated less powerful and shorter-lived antibodies against the virus that causes COVID-19 than healthy people and those on other kinds of immunosuppressants, according to a study by researchers at Washington University School of Medicine in St. Louis. The scientists found this was especially apparent regarding the virus’s delta variant.