Global study quantifies rise in blood clots, heart inflammation following COVID-19 vaccination

Global Covid Vaccine Safety Project’s assessment on adverse events related to COVID-19 vaccines found that instances of blood clots and heart inflammation were at least 1.5 times more than expected following inoculation with mRNA and ChadOX1 vaccines

One of the largest assessments of its kind, spanning 99 million people and investigating reports of adverse reactions following COVID-19 vaccination, found that instances of Guillain Barre Syndrome, myocarditis, pericarditis and cerebral venous sinus thrombosis (CVST) were at least 1.5 times more than expected following inoculation with mRNA and ChadOX1 vaccines. This is in line with previous observations by the World Health Organization and the European Medicines Agency, and was what led to these being classified as ‘rare’ side effects following the vaccination for COVID-19.

The data set did not include patients from India. However, a majority of Indians were administered the ChAdOX1 or Covishield vaccines during the pandemic. The need for rapid development and administration of vaccines saw a range of new approaches to vaccination, namely, the use of synthetic viral particles or protein constructs being administered following shortened testing programmes.

Guillain-Barre syndrome is a disorder in which the immune system attacks the nerves. While rarely fatal, it can cause muscular damage and mean prolonged treatment. CVST refers to blood clots in the brain. Myocarditis and pericarditis are inflammation of the heart tissue. All of these are serious conditions and potentially fatal.

The Global Covid Vaccine Safety Project, which made the assessment, compiled electronic healthcare data on adverse events related to COVID-19 vaccines from participants across multiple sites, including Argentina, New South Wales and Victoria in Australia, British Columbia and Ontario in Canada, Denmark, Finland, France, New Zealand, and Scotland.

The analysis involved computing the so called OE ratios or observed versus expected ratios. This means first healthcare providers, having a baseline ‘expectation’ of how many adverse events are likely given a certain number of vaccinated people, and comparing it with the number of events actually reported to health systems. Expectations are formed based on experience with the rates of vaccination, and reactions observed historically. However, COVID-19 vaccination was an outlier event that saw billions of vaccines administered over a relatively short span. Ratios greater than 1.5 or, in other words, 50% more adverse-reaction reports than what is expected, are considered ‘potential safety signals’ or necessitating a thorough investigation.

“OE ratios >1.5 were observed for Guillain-Barré syndrome and cerebral venous sinus thrombosis (3.23) following the first dose of ChAdOx1 vaccine. Acute disseminated encephalomyelitis showed an OE ratio of 3.78 following the first dose of mRNA-1273 vaccine. The OE ratios for myocarditis and pericarditis following BNT162b2 (Pfizer/BioNTech), mRNA-1273 (Moderna), and ChAdOx1 (Oxford/AstraZeneca/Serum Institute of India) were significantly increased with ratios>1.5,” notes the study, published this month in the peer-reviewed journal Vaccine.

As on December 6, 2022 a total of 92,003 Adverse Events Following Immunisation (AEFI) have been reported in India since the start of the COVID-19 vaccination, the Union Health Ministry told Parliament. This is about 0.009% of Indians who took COVID-19 vaccines.