Evaluation of The Global COVID Vaccine Safety Project


A large study on the future directions unveiling COVID-19 vaccine safety and risks.

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The Global COVID Vaccine Safety (GCoVS) Project, initiated in 2021 within the multinational Global Vaccine Data Network (GVDN), serves to conduct a thorough examination of vaccine safety. The objective of this was to assess the risk of adverse events of special interest (AESI) after COVID-19 vaccination across 10 sites spanning 8 countries. This cross-national study verified known safety alerts concerning myocarditis, pericarditis, Guillain-Barré syndrome, and cerebral venous sinus thrombosis. Additionally, it pinpointed other potential safety concerns warranting deeper examination.

The study had 99,068,901 vaccinated individuals, with a total administration of 183,559,462 doses of BNT162b2, 36,178,442 doses of mRNA-1273, and 23,093,399 doses of ChAdOx1 across participating sites. Risk periods following homologous vaccination schedules they contributed to 23,168,335 person-years of follow-up. Observed-to-expected (OE) ratios with lower bounds of the confidence interval (LBCI) greater than 1.5 were noted for Guillain-Barré syndrome (2.49, 95% CI: 2.15, 2.87) and cerebral venous sinus thrombosis (3.23, 95% CI: 2.51, 4.09) after the initial dose of the ChAdOx1 vaccine.

3 Key Takeaways

  1. The GCoVS Project, conducted within the multinational GVDN, aimed to assess the risk of AESI after COVID-19 vaccination across diverse populations and geographical locations.
  2. The study verified known safety signals such as myocarditis, pericarditis, Guillain-Barré syndrome, and cerebral venous sinus thrombosis associated with COVID-19 vaccination, indicating the importance of ongoing surveillance and monitoring.
  3. The research identified other potential safety signals warranting deeper examination, emphasizing the need for continued research to ensure the safety and efficacy of COVID-19 vaccines.

“The risk up to 42 days after vaccination was generally similar to the background risk for the majority of outcomes; however, a few potential safety signals were identified. We observed potential safety signals for GBS and CVST after the first dose of ChAdOx1 based on more than 12 million doses administered,” according to the investigators. “Overall, studies of the vector-based vaccines such as the ChAdOx1, have observed a higher incidence of GBS after vaccination compared with the background incidence, whereas, most studies of the mRNA vaccines, such as BNT162b2 and mRNA-1273, have not observed increases of GBS.”

Acute disseminated encephalomyelitis exhibited an OE ratio of 3.78 (95% CI: 1.52, 7.78) following the first dose of the mRNA-1273 vaccine. Furthermore, the OE ratios for myocarditis and pericarditis following BNT162b2, mRNA-1273, and ChAdOx1 were significantly elevated with LBCIs exceeding 1.5.

“This multi-country cohort study was conducted in the unique setting of the GVDN,” according to the investigators. “The number of such large systematically coordinated studies across diverse geographical locations and populations is limited. Several studies have previously assessed the risks of the identified safety signals following COVID-19 vaccination, primarily in single-site settings. We investigated the association between COVID-19 vaccination and 13 AESIs comprising neurological, haematological, and cardiovascular conditions across countries including Europe, North America, South America, and Oceania.”

Expected rates were derived from pre-COVID-19 vaccination healthcare data provided by participating sites, stratified by age and sex. Observed rates were documented from the same healthcare datasets following the rollout of the COVID-19 vaccination program. Risk evaluations were conducted using OE ratios accompanied by 95% confidence intervals. Identified priority safety signals were those exhibiting a 95% LBCI exceeding 1.5.

The study has limitations including variability in data collection, quality, and reporting standards across countries introduces potential bias. Diverse vaccination strategies across participating sites complicate result interpretation. Unadjusted confounding factors like pre-existing health conditions and demographics may affect the validity of multi-country analyses. Potential underreporting across countries may have underestimated safety signals. Assessing safety signals should consider rarity, severity, and clinical relevance. Overall risk-benefit evaluations should account for infection-associated risks. Lastly, the varying specificity and sensitivity of ICD-10 codes across countries require cautious interpretation.

In summary, within the multi-country framework of the GVDN and the GCoVS Project, observed versus expected analyses benefit from a larger dataset, improving generalizability and statistical power. While the study confirmed known safety signals and provided evidence on additional outcomes, further investigation is necessary to validate associations and assess clinical significance.


Faksova K, Walsh D, Jiand Y, et. al. COVID-19 vaccines and adverse events of special interest: A multinational Global Vaccine Data Network (GVDN) cohort study of 99 million vaccinated individuals. Published April 2, 2024. Accessed May 14, 2024. doi: https://doi.org/10.1016/j.vaccine.2024.01.100

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