[Thrombosis with Thrombocytopenia Syndrome following adenovirus vector-based vaccines to prevent COVID-19: epidemiology and clinical presentation in Spain].

BACKGROUND

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

METHODS

We included all venous or arterial thrombosis with thrombocytopenia following adenovirus vector-based vaccines (AstraZeneca or Janssen) to prevent COVID-19 disease between February 1 and September 26, 2021. We describe the crude rate and the standardized morbidity ratio. We assessed the predictors of mortality.

RESULTS

Sixty-one cases were reported and 45 fulfilled eligibility criteria, 82% women. The crude TTS rate was 4/1,000,000 doses and 14-15/1,000,000 doses between 30-49 years. The number of observed cases of cerebral venous thrombosis was 6-18 higher than the expected in patients younger than 49 years. Symptoms started 10 (interquartile range (IQR): 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% (95% CI: 49-78%) had D-dimer >2000 ng/mL. Patients had multiple location thrombosis in 36% and fatal outcome in 24% cases. A platelet nadir <50,000 /μL (odds ratio (OR): 7.4; CI 95%: 1.2-47.5) and intracranial hemorrhage (OR: 7.9; IC95%: 1.3-47.0) were associated with fatal outcome.

CONCLUSION

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