New Delhi: Covid-19 vaccines, including those from Moderna, Pfizer and Oxford, have been linked with a slight increase in heart, brain, and blood disorders, according to a new study. The Pfizer/BioNTech and Moderna Covid-19 vaccines are mRNA vaccines, while the Oxford-AstraZeneca vaccine, the formula of which was replicated by the Serum Institute of India (SII) to manufacture Covishield, is an adenovirus-vector vaccine. In the Oxford-AstraZeneca vaccine, a modified version of a chimpanzee adenovirus called ChAdOx1 is used as a vector to deliver the genetic material of SARS-CoV-2 so that it can enter the cells of a human or another host but not replicate inside. From this genetic material, cells receive information to make the spike protein of SARS-CoV-2.
The study included 99 million people from 10 sites across eight countries.
New Delhi: Conducted by the Global Vaccine Data Network (GVDN), a multinational research network with primary interests in the area of vaccine safety and development, the study was published in the journal Vaccine. Researchers investigated 13 heart, blood, and neurological conditions to determine if there is a greater chance of them occurring after one receives a Covid-19 vaccine.
These conditions included myocarditis, pericarditis, Guillain-Barré syndrome, cerebral venous sinus thrombosis, transverse myelitis, and acute disseminated encephalomyelitis.
Pre-established safety signals for myocarditis, which refers to inflammation of the heart muscle, and pericarditis, which is defined as the inflammation of the thin sac covering the heart (pericardium), were identified in those who received mRNA vaccines.
Pre-established safety signals are information on known adverse events that are potentially caused by a drug or a vaccine, and need further investigation, according to the European Medicines Agency.
In the people who received viral vector vaccines, pre-established safety signals for Guillain-Barré syndrome, which is a rare autoimmune disorder that affects nerves and causes muscle weakness and tingling sensations, and cerebral venous sinus thrombosis, a condition in which a blood clot is formed in the brain’s venous sinuses as a result of which drainage of blood from the brain is prevented, were observed.
For some conditions, possible safety signals were observed. A possible safety signal is information on a new adverse event that is potentially caused by a drug or vaccine. Such signals were identified for transverse myelitis, which refers to an inflammation in a part of the spinal cord, and acute disseminated encephalomyelitis, which is a neurological disorder characterised by widespread attacks of inflammation in the brain and spinal cord, in people who received viral vector and mRNA vaccines.
The study is an example of an observed versus expected analysis. The purpose of such an analysis is to detect potential vaccine safety signals. According to the World Health Organization, a vaccine safety signal refers to information indicating a potential link between a vaccine and an adverse health effect.
As part of the analysis, researchers examined if there is a greater risk for developing a medical condition in various time periods after receiving a vaccine, compared with a period before the vaccine was available.
The observed versus expected ratios for myocarditis and pericarditis following Pfizer, Moderna, and Oxford-AstraZeneca vaccines were significantly increased, the study said.
