Global and regional burden of vaccine-induced thrombotic thrombocytopenia, 1969-2023: Comprehensive findings with critical analysis of the international pharmacovigilance database.

OBJECTIVE: The scarcity of studies on vaccine-induced thrombosis and thrombocytopenia syndrome (TTS) limits the comprehensive understanding of vaccine safety on a global scale. Therefore, the objective of this study is to assess the global burden of vaccine-induced TTS, identify the vaccines most associated with it, and suggest clinical implications regarding vaccination. METHODS: This study employed the World Health Organization international pharmacovigilance database, extracting records of vaccine-induced immune thrombotic thrombocytopenia from 1969 to 2023 (total reports, n > 130 million). Global reporting counts, reported odds ratios (ROR), and information components (IC) were calculated to identify the association between 19 vaccines and the occurrence of vaccine-induced TTS across 156 countries. RESULTS: We identified 24 233 cases (male, n = 11 559 [47.7%]) of vaccine-induced TTS among 404 388 reports of all-cause TTS. There has been a significant increase in reports of vaccine-induced TTS events over time, with a noteworthy surge observed after 2020, attributed to cases of TTS associated with COVID-19 vaccines. Measles, mumps, and rubella (MMR) vaccines were associated with most TTS reports (ROR [95% confidence interval], 2.87 [2.75-3.00]; IC [IC0.25], 1.51 [1.43]), followed by hepatitis B (HBV, 2.23 [2.07-2.39]; 1.15 [1.03]), rotavirus diarrhea (1.95 [1.78-2.13]; 0.81 [0.53]), encephalitis (1.80 [1.50-2.16]; 0.84 [0.53]), hepatitis A (1.67 [1.50-1.86]; 0.73 [0.55]), adenovirus Type 5 vector-based (Ad5-vectored) COVID-19 (1.64 [1.59-1.68]; 0.69 [0.64]), pneumococcal (1.57 [1.49-1.66]; 0.65 [0.56]), and typhoid vaccines (1.41 [1.12-1.78]; 0.49 [0.11]). Concerning age and sex-specific risks, reports of vaccine-induced TTS were more associated with females and younger age groups. The age group between 12 and 17 years exhibited significant sex disproportion. Most of these adverse events had a short time to onset (days; mean [SD], 4.99 [40.30]) and the fatality rate was 2.20%, the highest rate observed in the age group over 65 years (3.79%) and lowest in the age group between 0 and 11 years (0.31%). CONCLUSION: A rise in vaccine-induced TTS reports, notably MMR, HBV, and rotavirus diarrhea vaccines, was particularly related to young females. Ad5-vectored COVID-19 vaccines showed comparable or lower association with TTS compared to other vaccines. Despite the rarity of these adverse events, vigilance is essential as rare complications can be fatal, especially in older groups. Further studies with validated reporting are imperative to improve the accuracy of assessing the vaccine-induced TTS for preventive interventions and early diagnosis.

How We Interpret Thrombosis with Thrombocytopenia Syndrome?

Platelets play an important role in hemostasis, and a low platelet count usually increases the risk of bleeding. Conditions in which thrombosis occurs despite low platelet counts are referred to as thrombosis with thrombocytopenia syndrome, including heparin-induced thrombocytopenia, vaccine-induced immune thrombotic thrombocytopenia, paroxysmal nocturnal hemoglobinuria, antiphospholipid syndrome, thrombotic microangiopathy (TMA), and disseminated intravascular coagulation. TMA includes thrombotic thrombocytopenic purpura, Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome (HUS), and atypical HUS. Patients with these pathologies present with thrombosis and consumptive thrombocytopenia associated with the activation of platelets and the coagulation system. Treatment varies from disease to disease, and many diseases have direct impacts on mortality and organ prognosis if therapeutic interventions are not promptly implemented. Underlying diseases and the results of physical examinations and general laboratory tests as part of a thorough workup for patients should promptly lead to therapeutic intervention before definitive diagnosis. For some diseases, the diagnosis and initial treatment must proceed in parallel. Utilization of not only laboratory tests but also various scoring systems is important for validating therapeutic interventions based on clinical information.

Analysis of hematologic adverse events reported to a national surveillance system following COVID-19 bivalent booster vaccination.

Hematologic complications, including vaccine-induced immune thrombotic thrombocytopenia (VITT), immune thrombocytopenia (ITP), and autoimmune hemolytic anemia (AIHA), have been associated with the original severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines. However, on August 31, 2022, new formulations of the Pfizer-BioNTech and Moderna vaccines were approved for use without clinical trial testing. Thus, any potential adverse hematologic effects with these new vaccines remain unknown. We queried the US Centers for Disease Control Vaccine Adverse Event Reporting System (VAERS), a national surveillance database, through February 3, 2023, all reported hematologic adverse events that occurred within 42 days of administration of either the Pfizer-BioNTech or Moderna Bivalent COVID-19 Booster vaccine. We included all patient ages and geographic locations and utilized 71 unique VAERS diagnostic codes pertaining to a hematologic condition as defined in the VAERS database. Fifty-five reports of hematologic events were identified (60.0% Pfizer-BioNTech, 27.3% Moderna, 7.3% Pfizer-BioNTech bivalent booster plus influenza, 5.5% Moderna bivalent booster plus influenza). The median age of patients was 66 years, and 90.9% (50/55) of reports involved a description of cytopenias or thrombosis. Notably, 3 potential cases of ITP and 1 case of VITT were identified. In one of the first safety analyses of the new SARS-CoV-2 booster vaccines, we identified few adverse hematologic events (1.05 per 1,000,000 doses), most of which could not be definitively attributed to vaccination. However, three reports of possible ITP and one report of possible VITT highlight the need for continued safety monitoring of these vaccines as their use expands and new formulations are authorized.

Ischemic Stroke and Vaccine-Induced Immune Thrombotic Thrombocytopenia following COVID-19 Vaccine: A Case Report with Systematic Review of the Literature.

INTRODUCTION: Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a prothrombotic syndrome observed after adenoviral vector-based vaccines for severe acute respiratory syndrome coronavirus 2. It is characterized by thrombocytopenia, systemic activation of coagulation, extensive venous thrombosis, and anti-platelet factor 4 antibodies. Arterial thrombosis is less common and mainly affects the aorta, peripheral arteries, heart, and brain. Several cases of ischemic stroke have been reported in VITT, often associated with large vessel occlusion (LVO). Here, we describe a case of ischemic stroke with LVO after Ad26.COV2.S vaccine, then we systematically reviewed the published cases of ischemic stroke and VITT following COVID-19 vaccination. METHODS: We describe a 58-year-old woman who developed a thrombotic thrombocytopenia syndrome with extensive splanchnic vein thrombosis and ischemic stroke due to right middle cerebral artery (MCA) occlusion, 13 days after receiving Ad26.COV2.S vaccination. Then, we performed a systematic review of the literature until December 3, 2021 using PubMed and EMBASE databases. The following keywords were used: ("COVID-19 vaccine") AND ("stroke"), ("COVID-19 vaccine") AND ("thrombotic thrombocytopenia"). We have selected all cases of ischemic stroke in VITT. RESULTS: Our study included 24 patients. The majority of the patients were females (79.2%) and younger than 60 years of age (median age 45.5 years). Almost all patients (96%) received the first dose of an adenoviral vector-based vaccine. Ischemic stroke was the presenting symptom in 18 patients (75%). Splanchnic venous thrombosis was found in 10 patients, and cerebral venous thrombosis in 5 patients (21%). Most patients (87.5%) had an anterior circulation stroke, mainly involving MCA. Seventeen patients (71%) had an intracranial LVO. We found a high prevalence of large intraluminal thrombi (7 patients) and free-floating thrombus (3 patients) in extracranial vessels, such as the carotid artery, in the absence of underlying atherosclerotic disease. Acute reperfusion therapy was performed in 7 of the 17 patients with LVO (41%). One patient with a normal platelet count underwent intravenous thrombolysis with alteplase, while 6 patients underwent mechanical thrombectomy. A malignant infarct occurred in 9 patients and decompressive hemicraniectomy was performed in 7 patients. Five patients died (21%). CONCLUSION: Our study points out that, in addition to cerebral venous thrombosis, adenoviral vector-based vaccines also appear to have a cerebral arterial thrombotic risk, and clinicians should be aware that ischemic stroke with LVO, although rare, could represent a clinical presentation of VITT.

Acute lower limb ischemia caused by vaccine-induced immune thrombotic thrombocytopenia: focus on perioperative considerations for 2 cases.

BACKGROUND: ChAdOx1 nCoV-19 (AstraZeneca) and Ad26COV2.S (Johnson & Johnson/Janssen) adenoviral vector vaccines have been associated with vaccine-induced immune thrombotic thrombocytopenia (VITT). Arterial thrombosis and acute limb ischemia have been described in a minority of patients with VITT. These patients usually need a revascularization, but they potentially are at a higher risk of complications. Optimal perioperative care of patients undergoing vascular surgery in acute VITT is unknown and important considerations in such context need to be described. CASES PRESENTATIONS: We report 2 cases of VITT presenting with acute limb ischemia who needed vascular surgery and we describe the multidisciplinary team decisions for specific treatment surrounding the interventions. Both patients' platelet counts initially increased after either intravenous immune globulin (IVIG) or therapeutic plasma exchange (TPE). None received platelet transfusion. They both received argatroban as an alternative to heparin for their surgery. Despite persistent positivity of anti-platelet factor 4 (PF4) antibodies and serotonin-release assay with added PF4 (PF4-SRA) in both patients, only one received a repeated dose of IVIG before the intervention. Per- and post-operative courses were both unremarkable. CONCLUSION: In spite of persistent anti-PF4 and PF4-SRA positivity in the setting of VITT, after platelet count improvement using either IVIG or TPE, vascular interventions using argatroban can show favorable courses. Use of repeated IVIG or TPE before such interventions still needs to be defined.

Successful Treatment of Vaccine-Induced Immune Thrombotic Thrombocytopenia in a 26-Year-Old Female Patient.

Vaccine-induced immune thrombotic thrombocytopenia (VITT) has already been described after vaccination with ChAdOx2 nCov-19 (AstraZeneca) and Ad26.COV2.S (Johnson & Johnson/Janssen). However, less knowledge so far has been gained about optimal therapeutic regimens in VITT-suspected patients. Here, we report the case of a 26-year-old female patient, who developed bilateral deep vein thrombosis in the lower legs and severe thrombocytopenia after ChAdOx2 nCov-19 vaccination. After initial anticoagulation therapy regimens including fondaparinux, apixaban, and danaparoid failed, the patient was successfully treated with high-dose intravenous immunoglobulins in combination with parental anticoagulation therapy with argatroban. As vaccination against severe acute respiratory syndrome coronavirus 2 affects billions of people worldwide, medical facilities and hospitals have to be prepared and provide effective treatment options in VITT-suspected patients, including rapid application of high-dose intravenous immunoglobulins, to improve patient outcomes.

Cerebral venous sinus thrombosis after adenovirus-vectored COVID-19 vaccination: review of the neurological-neuroradiological procedure.

Cerebral venous and sinus thrombosis (CVST) after adenovirus-vectored COVID-19 ChAdOx1 nCov-19 (Oxford-AstraZeneca) and Ad26.COV2.S (Janssen/Johnson & Johnson) is a rare complication, occurring mainly in individuals under 60 years of age and more frequently in women. It manifests 4-24 days after vaccination. In most cases, antibodies against platelet factor-4/polyanion complexes play a pathogenic role, leading to thrombosis with thrombocytopenia syndrome (TTS) and sometimes a severe clinical or even fatal course. The leading symptom is headache, which usually increases in intensity over a few days. Seizures, visual disturbances, focal neurological symptoms, and signs of increased intracranial pressure are also possible. These symptoms may be combined with clinical signs of disseminated intravascular coagulation such as petechiae or gastrointestinal bleeding. If TTS-CVST is suspected, checking D-dimers, platelet count, and screening for heparin-induced thrombocytopenia (HIT-2) are diagnostically and therapeutically guiding. The imaging method of choice for diagnosis or exclusion of CVST is magnetic resonance imaging (MRI) combined with contrast-enhanced venous MR angiography (MRA). On T2*-weighted or susceptibility weighted MR sequences, the thrombus causes susceptibility artefacts (blooming), that allow for the detection even of isolated cortical vein thromboses. The diagnosis of TTS-CVST can usually be made reliably in synopsis with the clinical and laboratory findings. A close collaboration between neurologists and neuroradiologists is mandatory. TTS-CVST requires specific regimens of anticoagulation and immunomodulation therapy if thrombocytopenia and/or pathogenic antibodies to PF4/polyanion complexes are present. In this review article, the diagnostic and therapeutic steps in cases of suspected TTS associated CSVT are presented.

Vaccine-induced immune thrombotic thrombocytopenia in a male after Ad26.COV2.S vaccination presenting as cerebral venous sinus thrombosis.

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare and life-threatening complication that can occur after COVID-19 vaccination. After the first reports of VITT and CVST in 2021 after Ad26.COV2.S vaccination, the FDA and CDC recommended an emergency pause on 13 April 2021, and after extensive safety reviews, on 23 April 2021, the CDC's Advisory Committee on Immunization Practices (ACIP) reaffirmed its original recommendation for use of the Ad26.COV2.S vaccination. As of 31 August 2021, in the United States, 54 cases of VITT following Ad26.COV2.S vaccination (37 female, 17 male) have been reported out of 14.1 million total shots given, 29 of which had cerebral venous sinus thrombosis (CVST). With more data, on 16 December 2021, the CDC endorsed the ACIP recommendations for individuals to receive an mRNA COVID-19 vaccine in preference over the Ad26.COV2.S vaccination. We report a rare case of a male with confirmed VITT and CVST following Ad26.COV2.S vaccination.

Immune complexes, innate immunity, and NETosis in ChAdOx1 vaccine-induced thrombocytopenia.

AIMS: We recently reported five cases of vaccine-induced immune thrombotic thrombocytopenia (VITT) 7-10 days after receiving the first dose of the ChAdOx1 nCoV-19 adenoviral vector vaccine against corona virus disease 2019 (COVID-19). We aimed to investigate the pathogenic immunological responses operating in these patients. METHODS AND RESULTS: We assessed circulating inflammatory markers by immune assays and immune cell phenotyping by flow cytometry analyses and performed immunoprecipitation with anti-platelet factor (PF)4 antibody in plasma samples followed by mass spectrometry from all five patients. A thrombus was retrieved from the sinus sagittal superior of one patient and analysed by immunohistochemistry and flow cytometry. Precipitated immune complexes revealed multiple innate immune pathway triggers for platelet and leucocyte activation. Plasma contained increased levels of innate immune response cytokines and markers of systemic inflammation, extensive degranulation of neutrophils, and tissue and endothelial damage. Blood analyses showed activation of neutrophils and increased levels of circulating H3Cit, dsDNA, and myeloperoxidase-DNA complex. The thrombus had extensive infiltration of neutrophils, formation of neutrophil extracellular traps (NETs), and IgG deposits. CONCLUSIONS: The results show that anti-PF4/polyanion IgG-mediated thrombus formation in VITT patients is accompanied by a massive innate immune activation and particularly the fulminant activation of neutrophils including NETosis. These results provide novel data on the immune response in this rare adenoviral vector-induced VITT.

Autoimmune Diseases Affecting Hemostasis: A Narrative Review.

Hemostasis reflects a homeostatic mechanism that aims to balance out pro-coagulant and anti-coagulant forces to maintain blood flow within the circulation. Simplistically, a relative excess of procoagulant forces can lead to thrombosis, and a relative excess of anticoagulant forces can lead to bleeding. There are a wide variety of congenital disorders associated with bleeding or thrombosis. In addition, there exist a vast array of autoimmune diseases that can also lead to either bleeding or thrombosis. For example, autoantibodies generated against clotting factors can lead to bleeding, of which acquired hemophilia A is the most common. As another example, autoimmune-mediated antibodies against phospholipids can generate a prothrombotic milieu in a condition known as antiphospholipid (antibody) syndrome (APS). Moreover, there exist various autoimmunity promoting environments that can lead to a variety of antibodies that affect hemostasis. Coronavirus disease 2019 (COVID-19) represents perhaps the contemporary example of such a state, with potential development of a kaleidoscope of such antibodies that primarily drive thrombosis, but may also lead to bleeding on rarer occasions. We provide here a narrative review to discuss the interaction between various autoimmune diseases and hemostasis.

COVID-19, gender and estroprogestins, what do we know?

The new coronavirus disease-19 (COVID-19) pandemic has rapidly spread all around the world, eliciting many questions and doubts about the pathogenesis of the disease and treatment. Mortality has been related to a prothrombotic state. Risk factors for the infection and for severe forms of COVID-19 have still to be defined. According to data collected, women appear to be less prone to severe forms of the disease and their mortality was lower than for men. The role of female hormones in the modulation of inflammation may be the reason behind this gender gap.Considering the prothrombotic state activated by the virus, hormone therapies have been placed under investigation as possible increasing risk factors for severe forms. Moreover, new vaccines and their rare thrombotic side effects have increased the concern about this issue.The goal of this review is to go over the mechanisms that lead up to thrombosis during COVID-19, trying to explain the possible reasons why women seem to be naturally protected. The expert opinions about whether to continue/discontinue hormonal therapies are reviewed. Moreover, available data about the so-called 'vaccine induced immune thrombotic thrombocytopaenia' caused by vaccines against COVID-19 are discussed.

[Cerebral venous sinus thrombosis : An overview of causes, diagnostics and treatment]. / Sinus- und Hirnvenenthrombose : Ein Überblick über Ursachen, Diagnostik und Therapie.

In some cases, cerebral venous sinus thrombosis shows a fulminant progress but with an incidence of 1.32 cases per 100,000 person-years it is relatively rare. Nevertheless, the disease is responsible for around 0.5-1% of all stroke cases. The neurological examination often reveals nonspecific findings but especially in younger patients with acute to subacute position-dependent headaches, this differential diagnosis should definitely be considered. This article presents the most common causes, including a digression on vaccine-induced immune thrombotic thrombocytopenia (VITT) as well as recommendations for clinical, laboratory testing and imaging diagnostics. In addition, relevant complications with particular reference to epileptic seizures within the framework of the disease entity and guideline-based acute treatment and secondary prophylaxis are presented.

Successful venous thromboprophylaxis in a patient with vaccine-induced immune thrombotic thrombocytopenia (VITT): a case report of the first reported case in Thailand.

BACKGROUND: Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare but fatal complication of the Coronavirus Disease 2019 vaccine. The many reports of VITT have mostly been in the Caucasian population. Here, we present the first reported case in an Asian population. CASE PRESENTATION: A 26-year-old female had severe headache and severe thrombocytopenia 8 days after administration of the ChAdOx1 nCoV-19 vaccine developed by AstraZeneca. Although no thrombosis was demonstrated by imaging studies, she had very highly elevated d-dimer levels during hospitalization. Serology for antibodies against platelet factor 4 was positive on several days with very high optical density readings. We found that the antibody could induce spontaneous platelet aggregation without the presence of heparin. We decided to treat her with intravenous immunoglobulin, high-dose dexamethasone, and a prophylactic dose of apixaban. She improved rapidly and was discharged from the hospital 6 days after admission. Neither thrombocytopenia nor thrombosis was subsequently detected at the three-week follow-up. CONCLUSIONS: Despite the lower rate of thrombosis, VITT can occur in the Asian population. Early detection and prompt treatment of VITT can improve the patient's clinical outcome. Thromboprophylaxis with nonheparin anticoagulants also prevents clot formation.

Therapeutic plasma exchange (TPE) as a plausible rescue therapy in severe vaccine-induced immune thrombotic thrombocytopenia.

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is associated with high titers of immunoglobulin G class antibodies directed against the cationic platelet chemokine platelet factor 4 (PF4). These antibodies activate platelets via FcγIIa receptors. VITT closely resembles heparin-induced thrombocytopenia. Inflammation and tissue trauma substantially increase the risk for forming pathogenic PF4 antibodies. We therefore propose the use of therapeutic plasma exchange as rescue therapy in VITT to deplete antibodies plus factors promoting inflammation such as excess cytokines in the circulation as well as extracellular vesicles derived from activated platelets.

Thrombosis with thrombocytopenia syndrome associated with COVID-19 vaccines.

BACKGROUND: Current vaccines for the Coronavirus Disease of 2019 (COVID-19) have demonstrated efficacy with low risk of adverse events. However, recent reports of thrombosis with thrombocytopenia syndrome (TTS) associated with adenovirus vector vaccines have raised concern. OBJECTIVE: This narrative review summarizes the current background, evaluation, and management of TTS for emergency clinicians. DISCUSSION: TTS, also known as vaccine-induced immune thrombotic thrombocytopenia, is a reaction associated with exposure to the ChAdOx1 nCoV-19 (Oxford-AstraZeneca) and AD26.COV2·S (Johnson & Johnson) vaccine, which may result in thrombocytopenia and thrombotic events. There are several case series of patients diagnosed with TTS, but the overall incidence is rare. TTS is characterized by exposure to one of the aforementioned vaccines 4-30 days prior to presentation, followed by thrombosis, mild-to-severe thrombocytopenia, and a positive platelet factor-4 (PF4)-heparin enzyme-linked immunosorbent assay (ELISA). Thrombosis typically involves atypical locations, including cerebral venous thrombosis and splanchnic vein thrombosis. Evaluation should include complete blood count, peripheral smear, D-dimer, fibrinogen, coagulation panel, renal and liver function, and electrolytes, as well as PF4-heparin ELISA if available. Consultation with hematology is recommended if suspected or confirmed. Treatment may include intravenous immunoglobulin and anticoagulation, while avoiding heparin-based agents and platelet transfusion. CONCLUSIONS: With increasing vaccine distribution, it is essential for emergency clinicians to be aware of the evaluation and management of this condition.

Vaccine-Induced Immune Thrombotic Thrombocytopenia with Disseminated Intravascular Coagulation and Death following the ChAdOx1 nCoV-19 Vaccine.

Coronavirus is a novel human pathogen causing fulminant respiratory syndrome (COVID-19). Although COVID-19 is primarily a disease of the lungs with florid respiratory manifestations, there are increasing reports of cardiovascular, musculoskeletal, gastrointestinal, and thromboembolic complications. Developing an effective and reliable vaccine was emergently pursued to control the catastrophic spread of the global pandemic. We report a fatal case of vaccine-induced immune thrombotic thrombocytopenia (VITT) after receiving the first dose of the ChAdOx1 nCoV-19 vaccine. We attribute this fatal thrombotic condition to the vaccine due to the remarkable temporal relationship. The proposed mechanism of VITT is production of rogue antibodies against platelet factor-4 resulting in massive platelet aggregation. Healthcare providers should be aware of the possibility of such fatal complication, and the vaccine recipients should be warned about the symptoms of VITT.

Recent Advances in Anticoagulant Treatment of Immune Thrombosis: A Focus on Direct Oral Anticoagulants in Heparin-Induced Thrombocytopenia and Anti-Phospholipid Syndrome.

For more than 10 years, direct oral anticoagulants (DOACs) have been increasingly prescribed for the prevention and treatment of thrombotic events. However, their use in immunothrombotic disorders, namely heparin-induced thrombocytopenia (HIT) and antiphospholipid syndrome (APS), is still under investigation. The prothrombotic state resulting from the autoimmune mechanism, multicellular activation, and platelet count decrease, constitutes similarities between HIT and APS. Moreover, they both share the complexity of the biological diagnosis. Current treatment of HIT firstly relies on parenteral non-heparin therapies, but DOACs have been included in American and French guidelines for a few years, providing the advantage of limiting the need for treatment monitoring. In APS, vitamin K antagonists are conversely the main treatment (+/- anti-platelet agents), and the use of DOACs is either subject to precautionary recommendations or is not recommended in severe APS. While some randomized controlled trials have been conducted regarding the use of DOACs in APS, only retrospective studies have examined HIT. In addition, vaccine-induced immune thrombotic thrombocytopenia (VITT) is now a part of immunothrombotic disorders, and guidelines have been created concerning an anticoagulant strategy in this case. This literature review aims to summarize available data on HIT, APS, and VITT treatments and define the use of DOACs in therapeutic strategies.

Coagulopathies after Vaccination against SARS-CoV-2 May Be Derived from a Combined Effect of SARS-CoV-2 Spike Protein and Adenovirus Vector-Triggered Signaling Pathways.

Novel coronavirus SARS-CoV-2 has resulted in a global pandemic with worldwide 6-digit infection rates and thousands of death tolls daily. Enormous efforts are undertaken to achieve high coverage of immunization to reach herd immunity in order to stop the spread of SARS-CoV-2 infection. Several SARS-CoV-2 vaccines based on mRNA, viral vectors, or inactivated SARS-CoV-2 virus have been approved and are being applied worldwide. However, the recent increased numbers of normally very rare types of thromboses associated with thrombocytopenia have been reported, particularly in the context of the adenoviral vector vaccine ChAdOx1 nCoV-19 from Astra Zeneca. The statistical prevalence of these side effects seems to correlate with this particular vaccine type, i.e., adenoviral vector-based vaccines, but the exact molecular mechanisms are still not clear. The present review summarizes current data and hypotheses for molecular and cellular mechanisms into one integrated hypothesis indicating that coagulopathies, including thromboses, thrombocytopenia, and other related side effects, are correlated to an interplay of the two components in the vaccine, i.e., the spike antigen and the adenoviral vector, with the innate and immune systems, which under certain circumstances can imitate the picture of a limited COVID-19 pathological picture.

Delayed headache after COVID-19 vaccination: a red flag for vaccine induced cerebral venous thrombosis.

BACKGROUND: Headache is a frequent symptom following COVID-19 immunization with a typical onset within days post-vaccination. Cases of cerebral venous thrombosis (CVT) have been reported in adenovirus vector-based COVID-19 vaccine recipients. FINDINGS: We reviewed all vaccine related CVT published cases by April 30, 2021. We assessed demographic, clinical variables and the interval between the vaccination and onset of headache. We assessed whether the presence of headache was associated with higher probability of death or intracranial hemorrhage. We identified 77 cases of CVT after COVID-19 vaccination. Patients' age was below 60 years in 74/77 (95.8%) cases and 61/68 (89.7%) were women. Headache was described in 38/77 (49.4%) cases, and in 35/38 (92.1%) was associated with other symptoms. Multiple organ thrombosis was reported in 19/77 (24.7%) cases, intracranial hemorrhage in 33/77 (42.9%) cases and 19/77 (24.7%) patients died. The median time between vaccination and CVT-related headache onset was 8 (interquartile range 7.0-9.7) days. The presence of headache was associated with a higher odd of intracranial hemorrhage (OR 7.4; 95% CI: 2.7-20.8, p < 0.001), but not with death (OR: 0.51, 95% CI: 0.18-1.47, p = 0.213). CONCLUSION: Delayed onset of headache following an adenovirus vector-based COVID-19 vaccine is associated with development of CVT. Patients with new-onset headache, 1 week after vaccination with an adenovirus vector-based vaccine, should receive a thorough clinical evaluation and CVT must be ruled out.

Uncommon thrombotic complications after SARS-CoV-2 vaccination.

Shortly after the worldwide initiation of vaccination against SARS-CoV-2, concerns emerged about a possible link between vaccination, severe thrombocytopenia, and the development of atypical venous thrombosis. Concerns were primarily about AstraZeneca (ChAdOx1 nCov-19), later Johnson & Johnson (Ad26.COV2.S), but cases of acute immune thrombocytopenic purpura (ITP) and bleeding without thrombosis and also atypical venous thrombosis after exposure to the messenger RNA-based vaccines produced by Pfizer-BioNTech and Moderna have been reported. Examination of the circumstances of these complications revealed that this is a similar mechanism to heparin-induced thrombocytopenia (HIT), a prothrombotic thrombocytopenic hypercoagulable disorder with venous and arterial thrombosis. HIT is caused by platelet-activating IgG antibodies directed against an antigen that is a macromolecular complex consisting of platelet factor 4 (PF4) and heparin. Naming this new entity vaccine-induced immune thrombotic thrombocytopenia (VITT) was suggested to avoid confusion with HIT. Patients had high levels of antibodies to the immune complex formed by PF 4 and the polyanionic component of the vaccine (double-stranded DNA). In patients with thrombosis at any vascular site after vaccination, accompanied by absolute or relative thrombocytopenia and systemic manifestations, HIT Ig ELISA assay to detect antibodies against PF4 and platelet-activating functional tests may be used for VITT recognition and differentiation from venous thromboembolic disease. Immune globulin impedes antibody-mediated platelet clearance and down-regulate platelet activation by immune complexes, as in HIT. It is prudent to choose from among the nonheparin antithrombotic agents - direct oral F.Xa inhibitors, direct thrombin inhibitors and indirect F.Xa inhibitors for the treatment of thrombosis.