New Delhi,  A population-level study has provided reassuring data on the risk of kidney disease relapse after Covid vaccination and the second or third dose of vaccine was associated with "higher relative risk but low absolute increased risk" of glomerular disease relapse.

Glomerular disease reduces the kidneys' ability to maintain a balance of certain substances in the bloodstream.

In a population-level study of 1,105 adults with stable glomerular disease (a type of autoimmune kidney disease), a first dose of a vaccine was not associated with relapse risk; however, receiving a subsequent vaccine dose was associated with a two-fold higher relative risk of relapse.

Importantly, the increase in absolute risk associated with vaccination was low (1-5 per cent depending on type of glomerular disease), and most vaccine-associated disease flares were mild, said the study published in Journal of the American Society of Nephrology.

People with glomerular diseases face a high risk of developing serious infections, and are more likely to experience complications of infections such as from Covid-19.

As vaccination programmes were rolled out, individual case reports began to emerge describing flares of glomerular disease that occurred within days to weeks of vaccines, suggesting the vaccine itself may have induced a flare of the autoimmune kidney disease.

To provide clarity, a team led by Sean Barbour (University of British Columbia) and Mark Canney (University of Ottawa) studied information on all patients in British Columbia, Canada who had the following glomerular diseases and other related conditions.

The analysis identified 1,105 adults with glomerular disease that was stable when Covid-19 vaccines first became available.

The exposure to a second or third dose was associated with a two-fold higher relative risk of relapse. Most vaccine-associated disease flares were mild, with approximately one in five people needing any change in treatment.

"These results indicate that although Covid-19 vaccines may be associated with a small increase in risk of causing a flare of glomerular disease, this risk is very small, and the well-established benefits of vaccination more than outweigh these risks," said Dr Barbour.

"This should encourage people with glomerular disease to continue to get regular Covid-19 vaccinations. Our findings also suggest that people with glomerular disease should have careful monitoring after Covid-19 vaccinations to capture any early flare of their disease," the researchers noted.