The Hindu Explains | Why are adverse events after COVID-19 immunisation of concern, and what do experts say?

The story so far: Reports of rare blood clots occurring after COVID-19 vaccination have led some countries to limit the usage of AstraZeneca’s vaccine for certain categories of people, while other countries have paused the administration. The World Health Organization’s Global Advisory Committee on Vaccine Safety conducted a review of the latest evidence of rare adverse blood coagulation events with the AstraZeneca COVID-19 vaccine. It said, “A very rare new type of adverse event called Thrombosis with Thrombocytopenia Syndrome, involving unusual and severe blood clotting events associated with low platelet counts, has been reported after vaccination with COVID-19 vaccines Vaxzevria and Covishield.” Further, the WHO committee said that a specific case definition for TTS is being developed by the Brighton Collaboration to assist in identifying and evaluating reported TTS events and aid in supporting causality assessments. Actually, the risk is greater with COVID-19 infection than with the vaccine, I’m going with this point of view.” In fact, Panagis Galiatsatos and Robert Brodsky said in Hopkins Medicine, “Some people infected with SARS-COV-2 develop abnormal blood clotting … In the lungs, legs and elsewhere.” A recent study by researchers at the University of Oxford stated, “The risk of the rare blood clotting known as cerebral venous thrombosis following COVID-19 infection is around 100 times greater than normal, several times higher than it is post-vaccination or following influenza.” The authors counted the number of CVT cases diagnosed in the two weeks following the diagnosis of COVID-19, or after the first dose of a vaccine. You need to watch out for symptoms to indicate clotting, and you must know when it occurs — adverse effects usually occur four to 20 days after the first dose right now.” While fever, body pain and tiredness after vaccination last a couple of days and are not worrisome, symptoms of concern during this extended period include chest pain, persistent abdominal pain, shortness of breath, pain in the extremities, severe headache and blurry vision.