A study published on May 18, 2022, has examined associations between the administration of mRNA Covid-19 vaccines and Cerebral Venous Thrombosis (CVT).
The study, Association of Cerebral Venous Thrombosis with mRNA Covid-19 Vaccines: A disproportionality Analysis of the World Health Organisation Pharmacovigilance Database retrospectively analysed the occurrence of CVT against factors such as time of onset after vaccination, recovery outcomes, and death from adverse reactions following Covid-19 vaccination.
The ‘disproportionality analysis’ identified significant safety signals for CVT occurrence resulting from mRNA covid-19 vaccination.
Cerebral Venous Thrombosis is classified as a rare medical event that can lead to serious neurological outcomes, in which blood clots form in the cerebral veins of dural venous sinuses.
Identification factors of CVT can include headaches, stroke-related symptoms, and seizures.
Hematologic disorders, inflammatory diseases, pregnancy, malignancy, hormonal’s abnormality, and meningitis are identified as being the main risk factors of developing CVT.
While the study notes that the vaccines are effective against covid infection due to neutralization of antibody formations, it refers to the point that several side effects following vaccination have been reported, most notably that the vaccination can cause thrombosis through the mechanism related to the production of pathologic antibodies.
The study identifies that very few studies have researched the association between covid vaccination and CVT, but states that whilst a rare disease, cases of CVT have been reported since the commencement of the vaccine’s administration.
The study’s introduction includes the hypothesis that Covid-19 vaccines, particularly mRNA-based covid vaccines are related to an increased risk of CVT.
An analysis was performed based on data from the World Health Organization’s (WHO) VigiBase and ‘adverse drug reaction’ (ADR) safety reports from 130 countries, and national pharmacovigilance centers in all countries since 1967.
The ADRs relevant to mRNA-based covid vaccines and CVT were extracted from the WHO database, and analysed to confirm differences between daily occurrences of CVT as opposed to occurrences of reported vaccine related CVT.
The study used the disproportionality analysis method to determine potential safety signals from the WHO database:
“If the proportion of ADRs related to Covid-19 vaccinations is greater than those associated with subjects who have not received Covid-19 vaccinations, this suggests potential safety signals of ADRs for Covid-19 vaccinations.”
The study published:
“On 30 September 2021, 1513 ADR cased (0.09%) of CVT out of 1,730,636 reports were observed for the mRNA-based Covid-19 vaccines (BNT162b2 and mRNA-1273) and the ChAdOx1 nCoV-19 vaccine.”
“Of these, ADRs of CVT were reported as 756 (0.07%) out of 1,154,023 cases for the mRNA-based Covid-19 vaccines (620 (0.05%) for BNT162b2 and 136 (0.01%) for mRNA-1273) and 757 (0.13%) out of 577,124 cases for the ChAdOx1 nCoV-19 vaccine.”
The analysis noted that there was no significant difference in reports of CVT onset between men and women.
The analysis also noted that data showed the CVT onset in the less than 65-year age group was significantly earlier than for the over 65-year age group.
While CVT onset was within 28 days of covid-19 vaccination, there were significant differences identified between the time of CVT onset when grouped by vaccination.
The data confirmed that more than 90% of the patients were in serious condition, while 33% of patients did not recover or died.
The study showed that the ‘death outcome’ was higher for patients who had received the ChAdOx1 nCov-19 vaccine than for those who received the mRNA-based Covid-19 vaccines.
The study concluded that:
A significant signal of disproportionality of CVT was noted for all Covid-19 vaccines.
Potential safety signals for the development of CVT were noted in mRNA-based and nCov-19 vaccines compared to the entire ‘dataset.’
CVT occurred mainly within a few weeks of the mRNA-based Covid-19 vaccines.
The study was limited by the fact that some countries national drug-monitoring centers do not report ADRs.
While the study notes there was major public attention in April 2021 relating to third-dose vaccine induced thrombotic thrombocytopenia, the WHO VigiBase did not offer details on whether the onset of CVT occurred after the first or second vaccination dose in the extracted data.
The studies concluded,
“Our study demonstrated a potential safety signal for the occurrence of CVT for Covid-19 mRNA vaccination. It is necessary to be aware of the risk of CVT occurrence, even after Covid-19 mRNA vaccination.”