Three doses of COVID-19 vaccine fail to provide sufficient protection against the Omicron variant in patients with autoimmune rheumatic diseases, an observational study shows.

Korean researchers say the “exceptionally weak” immune response to the dominant SARS-CoV-2 strain seen in this at-risk population highlights their vulnerability to breakthrough infections.

Their findings are based on analyses of blood samples from 149 patients with rheumatoid arthritis, SLE and other autoimmune conditions, and 94 healthcare workers as controls.

Overall, the average cross-neutralising responses against Omicron infection developed following a third vaccine dose was around half that seen in controls (27% vs 50%, respectively).