Half of those with rare COVID-19 vaccine-induced thrombotic syndrome have CVST

More than 50% of individuals with thrombosis and thrombocytopenia syndrome linked to COVID-19 vector-based vaccine administration presented with cerebral venous sinus thrombosis, according to a study.

“There is a rapidly growing awareness of the urgency to better characterize the newly described ‘thrombosis and thrombocytopenia syndrome’ (TTS) in association with viral vector-based vaccines against SARS-CoV-2,” Lina Palaiodimou, MD, of the second department of neurology at Attikon University Hospital in Greece, and colleagues wrote in Neurology.

“Recent safety signals issued by national and international regulatory authorities of pharmacovigilance, along with an increasing number of published reports of cerebral venous sinus thromboses (CVST) and thromboses at unusual sites in combination with thrombocytopenia, have indicated the association of TTS with the viral vector-based SARS-CoV-2 vaccines: ChAdOx1 nCoV-19 (Vaxzevria, AstraZeneca/Oxford) and Ad26.COV2.S (Janssen/Johnson & Johnson),” they said

Reports have shown additional cases of CVST and thrombotic or thromboembolic events after COVID-19 vaccination that did not occur with thrombocytopenia. This raises “salient concerns” regarding distinguishing factors between TTS and other thromboses temporally associated with COVID-19 vaccination, according to the researchers.

Palaiodimou and colleagues conducted a systematic review and meta-analysis to determine the proportion of CVST among TTS cases and investigate its characteristics and outcomes. They included clinical trials, cohorts, case series and registry-based studies. Specifically, they sought to calculate the pooled mortality rate of CVST, TTS-linked CVST and TTS, as well as the pooled proportion of patients with CVST among patients with any thrombotic event and TTS. Clinical characteristics of patients with a thrombotic event after vaccination served as secondary outcomes.

In the qualitative analysis, the researchers included 69 studies featuring 370 patients with CVST and 4,182 patients with any thrombotic event linked to COVID-19 vector-based vaccine administration. In the quantitative meta-analysis, they included 23 studies.

Results showed a pooled proportion of CVST of 51% (95% CI, 36-66) among TTS cases. Palaiodimou and colleagues noted an independent association between TTS and increased risk for CVST compared with non-TTS patients with thrombotic events after vaccination (OR = 13.8; 95% CI, 2-97.3). Further, they reported pooled mortality rates of 28% (95% CI, 21-36) and 38% (95% CI, 27-49) for TTS and TTS-linked CVST, respectively. Thrombotic complications occurred within 2 weeks of receiving the COVID-19 vaccine, primarily among women younger than 45 years, even in the absence of pro-thrombotic risk factors.

“As the risk-benefit assessments provided by international regulatory authorities continue to emphasize the overwhelmingly favorable risk-benefit ratio for vaccination against SARS-CoV-2 in scenarios with high incidence rates, a sufficient characterization of TTS is pivotal for swift diagnosis and timely treatment initiation that may improve the dire prognosis of TTS patients following adenovirus vector-based vaccination,” Palaiodimou and colleagues wrote.