Study of 99 million people reveals two rare side effects from anti-COVID vaccines

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Two new but extremely rare side effects of the anti-Covid vaccine – a neurological disorder and inflammation of the spinal cord – have been discovered by researchers working on the largest vaccine safety study to date.

The study involving more than 99 million people from Australia, Argentina, Canada, Denmark, Finland, France, New Zealand and Scotland has confirmed how rare complications from the vaccine are, with researchers confirming that the benefits of anti-COVID vaccines still "pass the risks", reports The Guardian.

Researchers who were part of the Global Vaccine Data Network used health records in electronic systems to compare the rates of 13 brain, blood and heart diseases in people after receiving the Pfizer, Moderna or AstraZeneca vaccine, with the rate that might be expected these diseases were present in the population before the pandemic.

The study confirmed with a high level of accuracy the links between mRNA vaccines (Pfizer and Moderna) and the rare side effects of myocarditis and pericarditis (both heart diseases). It also confirmed Guillain-Barre syndrome (where the immune system attacks the nerves) and cerebral venous sinus thrombosis (a type of blood clot in the brain) as rare side effects linked to the AstraZeneca vaccine.

But a new, rare side effect, acute encephalomyelitis – inflammation and swelling in the brain and spinal cord – was identified in the data analysis as an effect linked to the AstraZeneca vaccine.

Not only did the Australian study confirm this disease as a rare side effect, but AstraZeneca's large amount of data allowed researchers to discover a second rare side effect, known as transverse myelitis, or inflammation of the spinal cord.

Julie Leask, an expert on vaccines, has said that the infection of COVID-19 increases the risk for some of these diseases "more than the vaccine".