The Oxford-AstraZeneca Covid vaccine, also known as Covishield in India was linked to a slightly increased risk of a mild bleeding disorder after the first dose, researchers have found.

In the study, published in the journal Nature Medicine, researchers examined the medical records of 5.4 million people in Scotland for instances of blood clots, unusual bleeding, and a condition called idiopathic thrombocytopenic purpura (ITP), The Guardian reported.

In ITP, a reduction in blood platelets can lead to easy bruising, bleeding gums and internal bleeding,

2.53 million adults had received their first doses of either the AstraZeneca vaccine or the one made by Pfizer-BioNTech. Of these, 1.7 million shots were the AstraZeneca vaccine.

They estimated that there are an additional 11 cases of ITP for every million doses of the AstraZeneca vaccine administered.

There was no sign of a greater risk from ITP, clotting or bleeding in the 800,000 people in Scotland who had received the Pfizer-BioNTech Covid vaccine up to 14 April.

The side-effect is mostly observed in older people with chronic health problems such as coronary heart disease, diabetes or chronic kidney disease, and typically appears from the second to fourth week.

The study also found that 48 percent of patients who developed ITP after a dose of AstraZeneca had prior prescriptions that could induce the condition.

"Our study suggests that there might be an increase in the risk of this very rare outcome for ChAdOx1 that is similar to other vaccines, including hepatitis B; measles, mumps and rubella; and influenza37,38," adding that this very small risk is important but needs to be seen within the context of the very clear benefits of the vaccine.

The study found weaker evidence for an increased risk of clots in the arteries and bleeding events after the AstraZeneca vaccine, The Guardian reported.

Reports of rare blood clotting has led a number of countries to limit the vaccine’s use of the AstraZeneca vaccine to older people, and a few other counries have dropped it altogether.