UPDATED: With comment from Auckland University Associate Professor Helen Petousis-Harris

The largest international vaccine study to date has found that COVID vaccines from Pfizer, Moderna and AstraZeneca have been linked to heart, brain and blood disorders.

But the Co-Director of the Global Vaccine Data Network said the risks were still “very small.”

The Auckland University hosted Global Vaccine Data Network assessed 13 neurological, blood, and heart related medical conditions to see if there was a greater risk of them occurring after receiving a Covid-19 vaccine.

It’s the latest of eight studies in the Global COVID Vaccine Safety (GCoVS) Project.

The data was sourced from information from 99 million people from 10 collaborator sites across eight countries.

The study identified the “pre-established safety signals” for myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the thin sac covering the heart) after mRNA vaccines, and Guillain-Barré syndrome (muscle weakness and changed sensation (feeling), and cerebral venous sinus thrombosis (type of blood clot in the brain) after viral vector vaccines.

“Possible safety signals for transverse myelitis (inflammation of part of the spinal cord) after viral vector vaccines and acute disseminated encephalomyelitis (inflammation and swelling in the brain and spinal cord) after viral vector and mRNA vaccines were identified.”

A large cohort study of 23.1 million residents across four Nordic countries revealed an increased risk of myocarditis among young males aged 16–24 years, based on 4–7 excess events in 28 days per 100,000 vaccinees after a second dose of the Pfizer BioNtech vaccine, and between 9 and 28 per 100,000 vaccinees after a second dose of Moderna COVID-19 vaccine.

The conclusion of this study was “this multi-country analysis confirmed pre-established safety signals for myocarditis, pericarditis, Guillain-Barré syndrome, and cerebral venous sinus thrombosis. Other potential safety signals that require further investigation were identified.”

Similarly, studies from British Columbia, Canada reported cases of myocarditis to be higher among those receiving a second dose compared with a third dose, and for those who received a second dose of the Moderna COVID-19 vaccine compared with the Pfizer BioNtech.

These findings were further investigated by the GVDN site in Victoria, Australia.

Their study and results are described in the accompanying paper.

Results are available for public review on GVDN’s interactive data dashboards.

These studies look at all people who received a vaccine and examine if there is a greater risk for developing a medical condition in various time periods after getting a vaccine compared with a period before the vaccine became available.

In a statement, Lead author Kristýna Faksová of the Department of Epidemiology Research, Statens Serum Institute, Copenhagen remarked that use of a common protocol and aggregation of the data through the GVDN makes studies like this possible.

“The size of the population in this study increased the possibility of identifying rare potential vaccine safety signals.

“Single sites or regions are unlikely to have a large enough population to detect very rare signals.”

Auckland University Associate Professor Helen Petousis-Harris, and Co-Director, Global Vaccine Data Network said “by making the data publicly available, we are able to support greater transparency, and stronger communications to the health sector and public.”

GVDN Co-Director Dr. Steven Black said, “GVDN supports a coordinated global effort to assess vaccine safety and effectiveness so that vaccine questions can be addressed in a more rapid, efficient, and cost-effective manner.

“We have a number of studies underway to build upon our understanding of vaccines and how we understand vaccine safety using big data.”

The research paper said “overall risk–benefit evaluations of vaccination should take the risk associated with infection into account, as multiple studies demonstrated higher risk of developing the events under study, such as GBS, myocarditis, or ADEM, following SARS-CoV-2 infection than vaccination.”

The Ministry of Health has been approached for comment.

Helen Petousis-Harris told Chris Lynch Media “the issue with myocarditis and the thrombosis events were identified soon after the vaccines came into use and the WHO, among other authorities, raised the alert early in 2021.

“The risk of these events following the vaccine is very small and even large clinical trials are too small to identify such rare events.

The risk after vaccine is far smaller than that associated with infection with the virus and vaccinated people have lower risks for these outcomes than unvaccinated.”

Petousis-Harris said “the evidence strongly supports the benefit of booster doses for those who they are recommended.

“The vaccine most commonly used in New Zealand is well established to be associated with a small risk of heart inflammation.

“The other conditions are related to viral vector vaccines. The ADEM  and TM has been followed up using an appropriate method to investigate association. This is published in the same issue of the Journal. indicated no increased risk following Pfizer mRNA vaccine.”