Vaccine‐induced immune thrombotic thrombocytopenia presenting with normal platelet count

Page, David; Zhu, Nancy; Sawler, Daniel; Sun, Hao; Turley, Elona; Pai, Menaka; Wu, Cynthia

doi:10.1002/rth2.12596

Cited by 12 publications

(6 citation statements)

References 16 publications

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“…Given clinicians’ knowledge of VITT and the recommendation of regulatory authorities to check platelet count in the presence of thrombosis ( 42 ), underreporting of low platelet count is unlikely, and data suggest that most thromboses observed in Vaxzevria recipients, despite being caused by vaccination, occur without thrombocytopenia (non-VITT thrombosis). Non-VITT thrombosis following Vaxzevria vaccination has been reported by case studies and shows a persistently normal platelet count and can occur both in the presence and in the absence of anti-PF4 antibodies ( 43 – 46 ).…”

Section: Venous Thrombosis In Recipients Of Adenovirus-based Vaccinesmentioning

confidence: 87%

Thrombotic events with or without thrombocytopenia in recipients of adenovirus-based COVID-19 vaccines

Cari

Alhosseini

Bergamo

et al. 2022

Front. Cardiovasc. Med.

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COVID-19, the severe acute respiratory syndrome, is one of the major emergencies that have affected health care systems. Drugs and oxygen are only partially effective in saving lives in patients with severe COVID-19, and the most important protection from death is vaccination. The widespread use of COVID-19 adenovirus-based vaccines has provided evidence for the occurrence of rare venous thrombotic events including cerebral venous thrombosis and splanchnic venous thrombosis in recipients of Vaxzevria and Jcovden vaccines and the review focus on them. One year ago, thromboses in Vaxzevria recipients have been associated with thrombocytopenia in the presence of antibodies to platelet factor 4 and have been called vaccine-induced immune thrombotic thrombocytopenia (VITT). The incidence of VITT is equal to 9-31 events per one million doses of vaccines as evaluated by health agencies worldwide and is higher in female and young vaccine recipients. More recently, by using the European EudraVigilance database, it has been demonstrated that the incidence of thrombosis in recipients of adenovirus-based vaccines is 5–10 fold higher than that of VITT and 7–12 fold higher than observed in the recipients of Comirnaty, an mRNA-based vaccine, suggesting that adenovirus-based vaccines cause not only VITT but also thrombosis without thrombocytopenia (non-VITT thrombosis). The incidence of the vaccine-dependent non-VITT thrombosis is different in the adenovirus-based vaccines and the VITT/non-VITT incidence ratio depends on the severity of thrombosis and is inversely related to the age of the recipients. The possible causes and clinical implications of non-VITT thrombosis in vaccine recipients are discussed.

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Section: Venous Thrombosis In Recipients Of Adenovirus-based Vaccinesmentioning

confidence: 87%

Thrombotic events with or without thrombocytopenia in recipients of adenovirus-based COVID-19 vaccines

Cari

Alhosseini

Bergamo

et al. 2022

Front. Cardiovasc. Med.

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“…Especially in the early phase of VITT and pre-VITT syndrome, platelets may remain within normal limits. 38 Similar to HIT, a further decrease in platelets compared with absolute platelet counts may more appropriately indicate ongoing platelet consumption. In vaccination-induced ITP, however, d -dimer levels are either normal or moderately increased.…”

Section: Discussionmentioning

confidence: 99%

Early recognition and treatment of pre-VITT syndrome after adenoviral vector-based SARS-CoV-2 vaccination may prevent from thrombotic complications: review of published cases and clinical pathway

Salih

Köhler

Schönborn

et al. 2022

European Heart Journal Open

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Aims Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare but highly morbid complication after adenoviral vector-based SARS-CoV-2 vaccination. The pre-VITT syndrome is defined as vaccine-induced immune thrombocytopenia without thrombosis typically presenting with new-onset headache. This review aims to identify at-risk patients before complications such as cerebral venous sinus thrombosis occur. Methods and Results We review previously published reports of 19 patients (median age 35 years, range 23-74; 16 females) who met the diagnostic criteria for a pre-VITT syndrome. Seven patients progressed to VITT, 12 patients did not. Patients who experienced VITT received delayed treatment. Median interval between the onset of headache and VITT-treatment (i.e., anticoagulation, immune globulins, or corticosteroids) was 5 days (range 1-8 days) compared to 2 days (0-5 days) in those without subsequent VITT (p = 0.033). The interval from onset of headache to anticoagulation was longer in patients with VITT (median 7 vs. 2 days; range 3-9 vs. 0-7 days; p = 0.01). Anticoagulation was safe in all patients with a pre-VITT syndrome as no hemorrhagic complications occurred after anticoagulation was started despite low platelets. The transient decline of platelet count after admission was significantly more pronounced in patients who progressed to VITT (median 67 vs. 0 * 103/µL; range 0-77 * 103/µL vs. 0-10 * 103/µL; p = 0.005). D-dimers did not differ between groups. Conclusion pre-VITT syndrome is a “red flag” and allows to identify and preemptively treat patients at-risk of further progression to VITT. However, it must be distinguished from post-vaccination immune thrombocytopenia.

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“…On the other hand, actual TTS cases may be missed, if, for instance, no thrombocytopenia-related term is coded as a reaction, or if the case represents a less typical presentation of TTS (e.g., with normal platelet count). 38 The inclusion of a specific term for TTS in MedDRA was essential, but only applicable to prospective cases.…”

Section: Case Studies Thrombosis With Thrombocytopenia Syndromementioning

confidence: 99%

Safety Monitoring of COVID‐19 Vaccines: Perspective from the European Medicines Agency

Durand

Dogné

Cohet

et al. 2023

Clin Pharma and Therapeutics

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Prior to deployment of COVID‐19 vaccines in the European Union (EU) in 2021, a high vaccine uptake leading to an unprecedented volume of safety data from spontaneous reports and real‐world evidence, was anticipated. The European Medicines Agency (EMA) implemented specific activities to ensure enhanced monitoring of emerging vaccine safety information, including intensive monitoring of reports of adverse events of special interest (AESIs) and the use of observed‐to‐expected (O/E) analyses. EMA also commissioned several independent observational studies using a large network of electronic healthcare databases and primary data collection via mobile and web‐based applications. This preparedness was key for two high‐profile safety signals: thrombosis with thrombocytopenia syndrome (TTS), a new clinical entity associated with adenovirus‐vectored vaccines, and myocarditis/pericarditis with messenger RNA (mRNA) vaccines. With no existing case definition nor background rates, the signal of TTS posed particular challenges. Nevertheless, it was rapidly identified, evaluated, contextualised and the risk minimised thanks to close surveillance and an efficient use of available evidence, clinical expertise and flexible regulatory tools. The two signals illustrated the complementarity between spontaneous and real‐world data, the former enabling rapid risk identification and communication, the latter enabling further characterisation. The COVID‐19 pandemic has tremendously enhanced the development of tools and methods to harness the unprecedented volume of safety data generated for the vaccines. Areas for further improvement include the need for better and harmonised data collection across Member States (e.g., stratified vaccine exposure) to support signal evaluation in all population groups, risk contextualisation and safety communication.

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Vaccine‐induced immune thrombotic thrombocytopenia presenting with normal platelet count

Cited by 12 publications

References 16 publications

Thrombotic events with or without thrombocytopenia in recipients of adenovirus-based COVID-19 vaccines

Thrombotic events with or without thrombocytopenia in recipients of adenovirus-based COVID-19 vaccines

Early recognition and treatment of pre-VITT syndrome after adenoviral vector-based SARS-CoV-2 vaccination may prevent from thrombotic complications: review of published cases and clinical pathway

Safety Monitoring of COVID‐19 Vaccines: Perspective from the European Medicines Agency

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