Vaccine Journal: Published: February, 2024

A multinational Global Vaccine Data Network (GVDN) cohort study of 99 million vaccinated individuals.

This study aimed to evaluate the risk of adverse events (13 medical conditions) of special interest (AESI) following COVID-19 vaccination from 10 sites across 8 countries. Most vaccine recipients were in the 20–39 and 40–59-year age groups.

The study was conducted by the Global COVID Vaccine Safety project and took into account 99,068,901 vaccinated individuals across eight countries: Argentina, Australia, Canada, Denmark, Finland, France, New Zealand and Scotland.

The report specifically looked at adverse events following administration of the Pfizer, Moderna and AstraZeneca Covid-19 vaccines.

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The researchers looked for 13 adverse events of special interest that occurred in vaccine recipients for up to 42 days after shots were administered. These conditions included Guillain-Barré syndrome, Bell’s palsy, convulsions, myocarditis and pericarditis.

Rare cases of Myocarditis were identified in the first, second and third doses of Pfizer-BioNTech’s and Moderna’s mRNA vaccines: The highest rate was seen after the second Moderna dose (6.1 times the expected rate of cases), according to the study published in the journal Vaccine.

Another heart condition called Pericarditis had a 6.9-fold increased risk in those who took a third dose of AstraZeneca’s viral-vector vaccine, while a first and fourth dose of Moderna’s vaccine had a 1.7-fold and 2.6-fold increased risk, respectively. 

There was a 2.5-times greater risk of developing the rare autoimmune disorder Guillain-Barre syndrome among those who took AstraZeneca’s vaccine compared to the rate researchers expected, and a 3.2-times greater risk of getting blood clots among the same population.

There was a 3.8-times greater risk of developing the neurological disorder Acute Disseminated EncephaloMyelitis (ADEM), after the Moderna vaccine was administered, and a 2.2-fold increased risk after AstraZeneca’s vaccine, according to the study.

However, the study noted that when it came to ADEM there was “no consistent pattern in terms of vaccine or timing following vaccination, and larger epidemiological studies have not confirmed any potential association.”

Conclusion

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.

The study, published in Vaccine, confirmed previously identified rare safety signals for myocarditis and pericarditis after a mRNA vaccine (Pfizer and Moderna) and Guillain-Barré syndrome and Cerebral Venous Sinus Thrombosis (CVST) after viral vector vaccines (AstraZeneca).

The international team of researchers emphasizes that the chances of getting any of these conditions are still very low. It's important to note that extensive research shows COVID-19 vaccines protect against serious illness, death, and long COVID symptoms. 

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