Switzerland: COVID-19 Vaccine Study

Researchers from the Global Vaccine Data Network, a research arm of the World Health Organization, analyzed 99 million people who received COVID-19 vaccinations across eight countries and revealed some risks associated with the shot.

According to the largest COVID-19 vaccine study to date, COVID-19 vaccines from companies like Moderna, Pfizer, and AstraZeneca were linked to rare occurrences of heart, brain, and blood disorders. However, experts say the risks of COVID-19 development greatly outweigh the risks of getting vaccinated.

The researchers looked at expected versus observed rates of 13 medical conditions that were considered “adverse events of special interest” in a study population of 99 million vaccinated people in eight countries, making it the largest COVID-19 vaccine study to date.

Covid vaccines are meant to prevent severe infection, and studies have shown Pfizer-BioNTech, Moderna, and AstraZeneca’s vaccines are effective at preventing severe illnesses, hospitalizations, and death.

The study, published in the journal Vaccine, found that the vaccine was tied to a slight increase in blood, neurological, and heart-related medical conditions, according to a press release from GVDN.

People who received certain types of mRNA vaccines were shown to have a higher risk of myocarditis, an inflammation of the heart muscle.

Some viral-vector vaccines were linked to a higher risk of blood clots in the brain, and an increased likelihood of Guillain-Barre syndrome, a neurological disorder in which the immune system attacks the nerves.

Other potential risks included inflammation of part of the spinal cord after viral vector vaccines and swelling and inflammation in the brain and spinal cord after viral vector and mRNA vaccines, the press release stated.

Key Findings of the Study

• 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).
• 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 after the Moderna vaccine was administered, and a 2.2-fold increased risk after AstraZeneca’s vaccine.

In the observational cohort study, K. Faksova, Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark, and colleagues compared observed expected rates of 13 selected AESI across neurological, haematological, and cardiac outcomes.

Expected rates were obtained by participating sites using pre-COVID-19 vaccination healthcare data stratified by age and sex. Observed rates were reported from the same healthcare datasets since the COVID-19 vaccination program rollout.

In conclusion, the COVID-19 vaccines from companies like Moderna, Pfizer, and AstraZeneca were linked to rare occurrences of brain, heart, and blood disorders, though experts say the risks of developing COVID-19 greatly outweigh the risks of getting vaccinated.

"While our study confirmed previously identified rare safety signals after COVID-19 vaccination and contributed evidence on several other important outcomes, further investigation is warranted to confirm associations and assess clinical significance," the researchers wrote.

Reference

Faksova, K., Walsh, D., Jiang, Y., Griffin, J., Phillips, A., Gentile, A., Kwong, J., Macartney, K., Naus, M., Grange, Z., Escolano, S., Sepulveda, G., Shetty, A., Pillsbury, A., Sullivan, C., Naveed, Z., Janjua, N., Giglio, N., Perälä, J., . . . Hviid, A. (2024). COVID-19 vaccines and adverse events of special interest: A multinational Global Vaccine Data Network (GVDN) cohort study of 99 million vaccinated individuals. Vaccine. https://doi.org/10.1016/j.vaccine.2024.01.100