Large-Scale Study Identifies Main Complications Following COVID-19 Vaccines

Researchers analyzed data from 99 million individuals to assess neurological, hematological, and cardiovascular complications after administering different types of vaccines. The study confirmed the risks of certain severe diagnoses, though scientists still describe the negative consequences in absolute terms as low.

Scientists from the Global Vaccine Data Network presented the results of the largest study to date on the safety of COVID-19 vaccines. They analyzed data from 99 million people across eight countries on different continents who received one of the following vaccines: Pfizer/BioNTech, Moderna, AstraZeneca, Sinopharm, Sinovac, Novavax, Johnson & Johnson, and the Russian “Sputnik”.

Despite the wide range of vaccines, the main research was conducted for the first three vaccines due to the highest number of vaccinations. For comparison, about 240 million doses were studied for Pfizer/BioNTech, Moderna, and AstraZeneca, while for the other vaccines combined, this figure was less than 350,000 doses.

The analysis identified increased risks of developing myocarditis, pericarditis, Guillain-Barre syndrome, transverse myelitis, facial nerve paralysis, acute disseminated encephalomyelitis, seizure disorders, as well as hematological complications — thrombosis, thrombocytopenia, and immune thrombocytopenia. These diagnoses are either already known complications or defined for the first time in the context of COVID-19 vaccines.

Such data was obtained thanks to the large sample size of participants. Until now, vaccine safety studies have been significantly limited by the number of volunteers. Nonetheless, the absolute number of complication cases remained low, as earlier smaller-scale studies had shown.

It is not yet clear whether the results will affect current vaccination protocols. Currently, some developers are improving vaccines, mainly to adapt them to specific SARS-CoV-2 strains. Meanwhile, at the end of last year, scientists in the USA upgraded mRNA COVID-19 vaccines, which showed a tenfold higher immune response.

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