Some long Covid patients show signs of autoimmune disease, study finds

Almost half of participants had harmful antibodies in their blood one year after infection

Blood samples from patients with long Covid, who are still suffering from fatigue and shortness of breath after a year, show signs of autoimmune disease, a new study has found.

Researchers say this finding offers clues about the nature of long Covid that could lead to improvements in diagnosing and treating the condition.

The study examined 106 people at three Canadian hospitals who had been diagnosed with Covid-19 between August 2020 and September 2021. Three, six and 12 months after recovery, the patients, and those in two control groups, were asked if they were suffering shortness of breath, coughing or fatigue.

Researchers also tested their blood for particular antibodies that contribute to autoimmune diseases.


Nearly 80 per cent of the patients had two or more of these antibodies in their blood three months and six months after the infection. This fell to 41 per cent after a year. Most of the healthy volunteers had no sign of these antibodies in their blood and in those who had experienced a non-Covid respiratory infection, levels of these antibodies were comparatively low.

Commenting on the study, Prof Jack Lambert, infectious diseases consultant at the Mater hospital in Dublin, said it has been clear since the end of 2020 that Covid-19 causes immune dysfunction by attacking white blood cells that fight infection. “That explains the crashes and flare-ups experienced by many long Covid sufferers, and it points to the need for greater focus on neuro-rehabilitation and immune repair.”

Prof Lambert has argued that the HSE response to long Covid is misplaced because it focuses on pulmonary issues in the post-acute phase after infection, rather than persistent neurological symptoms.

Autoimmune disease occurs when the immune system mistakenly attacks healthy parts of the body, instead of defending the body against disease. It causes conditions such as rheumatoid arthritis and lupus.

The study, published in the European Respiratory Journal, found two specific “autoantibodies”, along with other proteins called cytokines that cause inflammation, persisted in about 30 per cent of Covid patients a year after infection. This tended to be among those patients who were also still suffering with fatigue and shortness of breath.

“For the majority the patients in our study, even if they had autoantibodies soon after their infection, this resolved after 12 months,” said Dr Manali Mukherjee of McMaster University, Canada. “However, in some patients, autoantibodies persist, and these patients are more likely to continue suffering with symptoms and to need medical help.”

“These results point towards the need to test for signs of autoimmune disease in patients with symptoms of long Covid that last for a year or more.”

Paul Cullen

Paul Cullen

Paul Cullen is Health Editor of The Irish Times