The chances of adult recipients of the AstraZeneca coronavirus vaccine - made in India as Covishield - developing blood clots, even mild ones, is "very rare", AIIMS chief Dr Randeep Guleria told NDTV on Sunday.
Dr Guleria also said that such cases were uncommon - he estimated the odds at around "1 in a million or less" - and that no events had been reported in the country so far.
"This is a very rare side effect that was first thought to be a coincidence... now studies suggest a link to the vaccine. It is still very rare and not seen, so far, in India, although there are suggestions that one or two cases are here also," Dr Guleria said.
What is it?
"What happens is that 10 to 15 days after vaccination the patient shows symptoms of fatigue, body ache and has a general feeling of tiredness. Platelet (tiny blood cells that help your body form clots to stop bleeding) levels come down and along with that there is chance of increased clotting in the veins in the brain or in the abdomen, or intestinal veins," he explained.
He also said that this was akin to another disease called "heparin-induced thrombocytopenia", which is an auto-immune condition similar to that which forms the blood clots.
What should you look out for?
"Within two weeks of getting the vaccine if you have any symptoms - fatigue, body ache (specifically in the stomach) or drowsiness, then you must contact your doctor. If you have none of these symptoms past the 15-day mark, then you are ok... no need to worry," Dr Guleria said.
What is the treatment?
"If this happens then there is a treatment strategy in place - what we call IVIG (intravenous immunoglobulin) and other drugs," he said.
Dr Guleria stressed that cases of vaccine-related blood clots were rare in India, but did say that more data is needed to conclude definitively either way.
The Adverse Events Following Immunisation (AEFI) committee is investigating and a report is expected next week. An earlier report - on March 23 - showed no blood clotting case in India.
The government review was ordered after the European drug regulator said it had found a possible link between the vaccine and rare blood clotting issues in adults who had received the shot.
The regulator, however, said the advantages of the vaccine still outweighed the risks. Safety chief Peter Arlett was quoted by news agency AFP as saying the numbers were "extremely small".
Dr Guleria made that same point, saying that of the crores of Indians who had received at least one dose so far, no such adverse effect had been reported.
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