People who suffered a COVID-19 infection may be up to a year at high risk of developing autoimmune inflammatory rheumatic diseases (AIRDs), according to a global study.

The study, published in Annals of Internal Medicine, showed that the risk increases with the severity of COVID, even among those who were vaccinated.

“However, these findings are based entirely on comparisons between groups infected with SARS-CoV-2 and those that are not, which might be biased by differences in health-seeking behaviour and inherent risk factors within the groups,” said the researchers from South Korea, Spain, the US and the UK.

To probe the effect of COVID-19 on long-term risk for AIRDs, the team from Kyung Hee University in Seoul conducted a study on two general population-based cohort studies involving more than 10 million Korean and 12 million Japanese adults.

The data included those with COVID between January 2020 and December 2021, matched to patients with influenza infection and uninfected control patients. The data was assessed for onset of AIRD at 1, 6, and 12 months after COVID or influenza.

The results showed an increased risk for AIRD up to 12 months after COVID-19, and the risk surged with the severity of COVID-19.

“SARS-CoV-2 infection was associated with increased risk for AIRD compared with matched patients without SARS-CoV-2 infection or with influenza infection. The risk for AIRD was higher with greater severity of acute COVID-19,” the researchers wrote in the paper.

While COVID vaccination cut down AIRD risk, it was still high for those who had severe COVID despite vaccination, they said