Thrombosis with thrombocytopenia syndrome following adenovirus vector-based vaccines to prevent COVID-19: Epidemiology and clinical presentation in Spain

Abstract

Background

We describe the epidemiological and clinical characteristics of thrombosis with thrombocytopenia syndrome (TTS) cases reported in Spain.

Methods

We included all cases of venous or arterial thrombosis with thrombocytopenia following administration of adenoviral vector vaccines (AstraZeneca or Janssen) against COVID-19 disease between 1 February and 26 September 2021. We describe the crude rate and the standardised morbidity ratio. We assessed the predictors of mortality.

Results

Sixty-one cases were reported and 45 fulfilled eligibility criteria; 82% of patients were women. The crude TTS rate was 4 cases/1 000 000 doses, and 14-15 cases/1 000 000 doses among patients aged 30-49 years. The number of observed cases of cerebral venous thrombosis was 6-18 times higher than that expected in patients younger than 49 years. Symptoms started a median (quartiles 1 and 3 [Q₁-Q₃]) of 10 (7-14) days after vaccination. Eighty percent (95% confidence interval [CI]: 65%-90%) had thrombocytopenia at the time of the emergency department visit, and 65% (49%-78%) had D-dimer levels > 2000 ng/mL. Patients had thromboses affecting multiple locations in 36% of cases and fatal outcomea in 24%. Platelet nadir < 50 000/μL (odds ratio [OR]: 7.4; 95% CI: 1.2-47.5) and intracranial hemorrhage (OR: 7.9; 95% CI: 1.3-47.0) were associated with fatal outcomes.

Conclusion

TTS must be suspected in patients with symptoms 10 days after vaccination and thrombocytopenia and/or elevated D-dimer levels.