Thrombotic Thrombocytopenia after ChAdOx1 nCoV-19 Vaccination

Vaccine-Induced Immune Thrombotic Thrombocytopenia: Clinicopathologic Features and New Perspectives on Anti-PF4 Antibody-Mediated Disorders

INTRODUCTION

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare yet severe adverse complication first identified during the global vaccination effort against SARS-CoV-2 infection, predominantly observed following administration of the ChAdOx1-S (Oxford-AstraZeneca) and Ad26.CoV2.S (Johnson & Johnson/Janssen) adenoviral vector-based vaccines. Unlike other anti-platelet factor 4 (PF4) antibody-mediated disorders, such as heparin-induced thrombocytopenia (HIT), VITT arises with the development of platelet-activating anti-PF4 antibodies 4-42 days post-vaccination, typically featuring thrombocytopenia and thrombosis at unusual sites.

AIM

To explore the unique properties, pathogenic mechanisms, and long-term persistence of VITT antibodies in patients, in comparison with other anti-PF4 antibody-mediated disorders.

DISCUSSION

This review highlights the complexity of VITT as it differs in antibody behavior and clinical presentation from other anti-PF4-mediated disorders, including the high incidence rate of cerebral venous sinus thrombosis (CVST) and the persistence of anti-PF4 antibodies, necessitating a re-evaluation of long-term patient care strategies. The nature of VITT antibodies and the underlying mechanisms triggering their production remain largely unknown.

CONCLUSION

The rise in awareness and subsequent prompt recognition of VITT is paramount in reducing mortality. As vaccination campaigns continue, understanding the role of adenoviral vector-based vaccines in VITT antibody production is crucial, not only for its immediate clinical implications, but also for developing safer vaccines in the future.

A Case of Dural Arteriovenous Fistula Following Cerebral Venous Sinus Thrombosis Associated with the COVID-19 Vaccine

Objective

Cerebral venous sinus thrombosis (CVST) is one of the rare and severe complications of coronavirus disease 2019 (COVID-19) vaccines. CVST has also been reported to develop into dural arteriovenous fistula; however, there were no reports of dural arteriovenous fistula associated with COVID-19 vaccine-induced cerebral venous sinus thrombosis. Here, we describe a rare case of a transverse-sigmoid sinus dural arteriovenous fistula followed by CVST due to COVID-19 vaccination.

Case Presentation

A 70-year-old patient presented with headache five days after receiving a second dose of COVID-19 vaccine. MRI showed a CVST in the superior sagittal sinus, left transverse sinus, and left sigmoid sinus. His headache improved after the administration of anticoagulant therapy. Six months later, a similar headache recurred, and cerebral angiography demonstrated a dural arteriovenous fistula in the left transverse sigmoid sinus and convexity dural arteriovenous fistulas in the left parietal cortex. The patient was treated twice with two sessions of transarterial embolization, and the shunts were completely occluded. His symptoms improved, and he was discharged with a modified Rankin Scale score of 0.

Conclusion

Dural arteriovenous fistula can develop after CVST in association with COVID-19 vaccination.

Acute Uveitis Following AstraZeneca COVID-19 Vaccination

PURPOSE

To report a case of bilateral acute uveitis following the first and subsequent doses of Oxford-AstraZeneca COVID-19 vaccination.

METHOD

A case report.

RESULTS

A 74-year-old Caucasian woman was presented with a one-day history of blurred vision, pain, photophobia, and redness in both eyes after receiving her first dose of the Oxford-AstraZeneca COVID-19 vaccine. Clinical evaluation confirmed bilateral anterior and intermediate uveitis six days later. Targeted diagnostic testing excluded infectious or autoimmune etiologies. After treatment with topical and oral corticosteroids, the patient had a resolution of symptoms with the recovery of visual function within seven weeks. Subsequently, she developed a recurrence of uveitis following the second dose of the Oxford-AstraZeneca COVID-19 vaccine, which required similar treatment, with slower tapering of corticosteroids over ten weeks. The patient had a full visual recovery.

CONCLUSION

Our case highlights the possibility of uveitis as an ocular complication of Oxford-AstraZeneca COVID-19 vaccination.

COVID-19 adenovirus vector vaccine induces higher interferon and pro-inflammatory responses than mRNA vaccines in human PBMCs, macrophages and moDCs

BACKGROUND

During the COVID-19 pandemic multiple vaccines were rapidly developed and widely used throughout the world. At present there is very little information on COVID-19 vaccine interactions with primary human immune cells such as peripheral blood mononuclear cells (PBMCs), monocyte-derived macrophages and dendritic cells (moDCs).

METHODS

Human PBMCs, macrophages and moDCs were stimulated with different COVID-19 vaccines, and the expression of interferon (IFN-λ1, IFN-α1), pro-inflammatory (IL-1β, IL-6, IL-8, IL-18, CXCL-4, CXCL-10, TNF-α) and Th1-type cytokine mRNAs (IL-2, IFN-γ) were analyzed by qPCR. In addition, the expression of vaccine induced spike (S) protein and antiviral molecules were studied in primary immune cells and in A549 lung epithelial cells.

RESULTS

Adenovirus vector (Ad-vector) vaccine AZD1222 induced high levels of IFN-λ1, IFN-α1, CXCL-10, IL-6, and TNF-α mRNAs in PBMCs at early time points of stimulation while the expression of IFN-γ and IL-2 mRNA took place at later times. AZD1222 also induced IFN-λ1, CXCL-10 and IL-6 mRNA expression in monocyte-derived macrophages and DCs in a dose-dependent fashion. AZD1222 also activated the phosphorylation of IRF3 and induced MxA expression. BNT162b2 and mRNA-1273 mRNA vaccines failed to induce or induced very weak cytokine gene expression in all cell models. None of the vaccines enhanced the expression of CXCL-4. AZD1222 and mRNA-1273 vaccines induced high expression of S protein in all studied cells.

CONCLUSIONS

Ad-vector vaccine induces higher IFN and pro-inflammatory responses than the mRNA vaccines in human immune cells. This data shows that AZD1222 readily activates IFN and pro-inflammatory cytokine gene expression in PBMCs, macrophages and DCs, but fails to further enhance CXCL-4 mRNA expression.

Only Subclinical Alterations in the Haemostatic System of People with Diabetes after COVID-19 Vaccination

People with diabetes have an increased risk of experiencing adverse COVID-19 outcomes. COVID-19 vaccination is, therefore, highly recommended. However, people with diabetes have an inherently elevated risk of thrombotic events and the impact of the vaccination on the coagulation system in this patient population remains to be elucidated. The aim of this study was to investigate the impact of COVID-19 vaccination on the haemostatic system in people with type 1 or type 2 diabetes. We evaluated the effects of COVID-19 vaccination (BioNTech Pfizer, Moderna, AstraZeneca) on standard coagulation parameters, whole blood coagulation (Thrombelastometry), platelet function (impedance aggregation), and thrombin generation (calibrated automated thrombography) in people with type 1 diabetes mellitus (n = 41) and type 2 diabetes mellitus (n = 37). Blood sampling points were prior to vaccination and two weeks after the respective vaccination. Thrombelastometry measurements indicated moderately increased clot formation post-vaccination in people with type 1, as well as with type 2, diabetes: "Clot formation times" were significantly shorter, and both "maximum clot firmness" and "alpha angles" were significantly higher, as compared to the respective pre-vaccination values. Therefore, TEM parameters were not altered after vaccination in patients receiving ASA. Moreover, platelet aggregation was enhanced in people with type 1 diabetes, and plasma levels of D-Dimer were increased in people with type 2 diabetes, following COVID-19 vaccination. All other standard coagulation parameters, as well as thrombin generation, were not affected by the vaccination. The coagulation responses of people with diabetes to COVID-19 vaccination were only subclinical and comparable to those observed in healthy individuals. Our findings suggest that people with diabetes do not face an increased activation of the coagulation post-vaccination.

Pilot Findings on SARS-CoV-2 Vaccine-Induced Pituitary Diseases: A Mini Review from Diagnosis to Pathophysiology

Since the emergence of the COVID-19 pandemic at the end of 2019, a massive vaccination campaign has been undertaken rapidly and worldwide. Like other vaccines, the COVID-19 vaccine is not devoid of side effects. Typically, the adverse side effects of vaccination include transient headache, fever, and myalgia. Endocrine organs are also affected by adverse effects. The major SARS-CoV-2 vaccine-associated endocrinopathies reported since the beginning of the vaccination campaign are thyroid and pancreas disorders. SARS-CoV-2 vaccine-induced pituitary diseases have become more frequently described in the literature. We searched PubMed/MEDLINE for commentaries, case reports, and case series articles reporting pituitary disorders following SARS-CoV-2 vaccination. The search was reiterated until September 2022, in which eight case reports were found. In all the cases, there were no personal or familial history of pituitary disease described. All the patients described had no previous SARS-CoV-2 infection prior to the vaccination episode. Regarding the type of vaccines administered, 50% of the patients received (BNT162b2; Pfizer-BioNTech) and 50% received (ChAdOx1 nCov-19; AstraZeneca). In five cases, the pituitary disorder developed after the first dose of the corresponding vaccine. Regarding the types of pituitary disorder, five were hypophysitis (variable clinical aspects ranging from pituitary lesion to pituitary stalk thickness) and three were pituitary apoplexy. The time period between vaccination and pituitary disorder ranged from one to seven days. Depending on each case's follow-up time, a complete remission was obtained in all the apoplexy cases but in only three patients with hypophysitis (persistence of the central diabetes insipidus). Both quantity and quality of the published data about pituitary inconveniences after COVID-19 vaccination are limited. Pituitary disorders, unlike thyroid disorders, occur very quickly after COVID-19 vaccination (less than seven days for pituitary disorders versus two months for thyroid disease). This is partially explained by the ease of reaching the pituitary, which is a small gland. Therefore, this gland is rapidly overspread, which explains the speed of onset of pituitary symptoms (especially ADH deficiency which is a rapid onset deficit with evocative symptoms). Accordingly, these pilot findings offer clinicians a future direction to be vigilant for possible pituitary adverse effects of vaccination. This will allow them to accurately orient patients for medical assistance when they present with remarkable symptoms, such as asthenia, polyuro-polydipsia, or severe headache, following a COVID-19 vaccination.

Immunvermittelte Sinus- und Hirnvenenthrombosen: VITT und prä-VITT als Modellerkrankung

In diesem Übersichtsartikel beschreiben wir die klinischen und paraklinischen Charakteristika der Vakzin-induzierten immunthrombotischen Thrombozytopenie (VITT) und fassen den gegenwärtigen Kenntnisstand zur Pathogenese zusammen. Bei der VITT bilden sich 5–20 Tage nach einer Impfung mit einem Adenovirus-vektorbasiertem SARS-CoV-2-Vakzin (AstraZeneca oder Johnson & Johnson) lebensbedrohliche Thrombosen aus, vor allem in den zerebralen Sinus und Hirnvenen. Laborchemisch zeigt sich eine typische Thrombozytopenie mit erhöhten D-Dimeren. Der Pathogenese liegen immunologische Prozesse zugrunde, die Ähnlichkeiten mit der Heparin-induzierten Thrombozytopenie aufweisen: so geht die VITT mit hochtitrigem Immunoglobulin G gegen das thrombozytäre Protein Plättchenfaktor 4 (PF4) einher. Durch die Interaktion mit dem Impfstoff wird PF4 so verändert, dass es von Antikörper-produzierenden Zellen des Immunsystems erkannt wird. Die so produzierten Anti-PF4-Antikörper führen über thrombozytäre FcγIIa-Rezeptoren zu einer Plättchenaktivierung. Der Nachweis plättchenaktivierender Anti-PF4-Antikörper bestätigt die Diagnose einer VITT. Antikoagulanzien, die die Bildung von Thrombin oder Thrombin selbst blockieren und hochdosiertes i. v.-Immunglobulin G, das die Fcγ-Rezeptor-vermittelte Zellaktivierung inhibiert, stellen die wirksame und kausale Behandlung der VITT dar. Bei Patienten mit katastrophalem Verlauf kann ein Plasmaaustausch versucht werden. Bei einigen Patienten ist ein prä-VITT Syndrom als Prodromalstadium zu beoachten, das sich typischerweise mit Kopfschmerzen manifestieren kann und dessen frühe Behandlung hilft, thrombotische Komplikationen zu vermeiden. Die spezifische Dynamik der VITT-assozierten Immunreaktion entspricht einer transienten, sekundären Immunantwort. Aktuelle Studien gehen der Frage nach, wie PF4 an unterschiedliche adenovirale Proteine bindet und beleuchten die Rolle von anderen Impfstoff-Bestandteilen als potentielle Liganden für die PF4-Bindung. Einige dieser Faktoren sind auch an der Etablierung eines proinflammatorischen Milieus („danger signal“) beteiligt, das unmittelbar nach der Impfung die 1. Phase der VITT-Pathogenese triggert. Sobald in der 2. Phase der VITT-Pathogenese hohe Titer von Anti-PF4-Antikörper gebildet sind, aktivieren diese neben Thrombozyten auch Granulozyten. In einem als NETose (von „neutrophil extracellular traps“) bezeichneten Prozess setzen aktivierte Granulozyten dabei DNA frei, mit der PF4 weitere Komplexe bildet, an die Anti-PF4-Antikörper binden. Dies verstärkt die Fcγ-Rezeptor-vermittelte Zellaktivierung weiter mit der Folge einer ausgeprägten Thrombin-Bildung. Zum Ende des Artikels geben wir einen Ausblick, welchen Einfluss die bisherigen Erkenntnisse zur VITT auf weitere globale Impfkampagnen gegen SARS-CoV-2 haben und beleuchten, wie Anti-PF4-Antikörper jenseits von VITT und HIT auch eine Rolle bei seltenen Erkrankungen spielen, die mit rezidivierenden venösen und arteriellen Thrombosen einhergehen.

Comparison of the safety and immunogenicity of the BNT-162b2 vaccine and the ChAdOx1 vaccine for solid organ transplant recipients: a prospective study

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and its resulting disease, coronavirus disease 2019 (COVID-19), has spread to millions of people worldwide. Preliminary data from organ transplant recipients have shown reduced seroconversion rates after the administration of different SARS-CoV-2 vaccination platforms. However, it is unknown whether different vaccination platforms provide different levels of protection against SARS-CoV-2. To answer this question, we prospectively studied 431 kidney and liver transplant recipients (kidney: n = 230; liver: n = 201) who received either the ChAdOx1 vaccine (n = 148) or the BNT-162b2 vaccine (n = 283) and underwent an assessment of immunoglobulin M/immunoglobulin G spike antibody levels. The primary objective of the study is to directly compare the efficacy of two different vaccine platforms in solid organ transplant recipients by measuring of immunoglobulin G (IgG) antibodies against the RBD of the spike protein (anti-RBD) two weeks after first and second doses. Our secondary endpoints were solicited specific local or systemic adverse events within 7 days after the receipt of each dose of the vaccine. There was no difference in the primary outcome between the two vaccine platforms in patients who received two vaccine doses. Unresponsiveness was mainly linked to diabetes. The rate of response after the first dose among younger older patients was significantly larger; however, after the second dose this difference did not persist (p = 0.079). Side effects were similar to those that were observed during the pivotal trials.

SARS-CoV-2 vaccines in children and adolescents: Can immunization prevent hospitalization?

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its variants of concern can infect people of all ages and can cause severe diseases in children, such as encephalitis, which require intensive care. Therefore, vaccines are urgently required to prevent severe disease in all age groups. We reviewed the safety and efficacy profiles of mRNA vaccines-BNT162b2 and mRNA-1273-demonstrated by clinical trials or observed in the real world. mRNA-1273 is effective in preventing SARS-CoV-2 infection in preschool children (6 months-6 years old). Both BNT162b2 and mRNA-1273 are effective in preventing SARS-CoV-2 infection in school-aged children and adolescents, thereby preventing post-coronavirus disease (COVID) conditions. The common side effects of vaccination are pain at the injection site, fatigue, and headache. Myocarditis and pericarditis are uncommon. Monitoring post-vaccination troponin levels may help prevent severe cardiac events. The SARS-CoV-2 coronavirus mutates its genome to overcome the herd immunity provided by mass vaccinations; therefore, we may need to develop new generations of vaccines, such as those using viral nucleocapsid proteins as antigens. In conclusion, the mRNA vaccines are generally safe and effective in preventing severe diseases and hospitalization among children and adolescents.

New-Onset Acute Kidney Disease Post COVID-19 Vaccination

The coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused an exceptional setback to the global economy and health. Vaccination is one of the most effective interventions to markedly decrease severe illness and death from COVID-19. In recent years, there have been increasingly more reports of new acute kidney injury (AKI) after COVID-19 vaccination. Podocyte injury, IgA nephropathy, vasculitis, tubulointerstitial injury, and thrombotic microangiopathy appear to be the main pathological phenotypes. Nonetheless, whether the link between the COVID-19 vaccine and acute kidney disease (AKD) is causal or coincidental remains to be verified. Here, we generalize some hypotheses for the emergence of AKD and its pathogenesis in response to certain COVID-19 vaccines. In fact, the enormous benefits of mass vaccination against COVID-19 in preventing COVID-19 morbidity and mortality cannot be denied. The purpose of this review is to assist in the clinical assessment and management of AKD following COVID-19 vaccination.

Coronavirus disease 2019 (COVID-19) vaccine platforms: how novel platforms can prepare us for future pandemics: a narrative review

More than 2 years after the explosion of the coronavirus disease 2019 (COVID-19) pandemic, extensive efforts have been made to develop safe and efficacious vaccines against infections with severe acute respiratory syndrome coronavirus 2. The pandemic has opened a new era of vaccine development based on next-generation platforms, including messenger RNA (mRNA)-based technologies, and paved the way for the future of mRNA-based therapeutics to provide protection against a wide range of infectious diseases. Multiple vaccines have been developed at an unprecedented pace to protect against COVID-19 worldwide. However, important knowledge gaps remain to be addressed, especially in terms of how vaccines induce immunogenicity and efficacy in those who are elderly. Here, we discuss the various vaccine platforms that have been utilized to combat COVID-19 and emphasize how these platforms can be a powerful tool to react quickly to future pandemics.

Pathogenesis of vaccine-induced immune thrombotic thrombocytopenia (VITT)

Vaccine-induced immune thrombotic thrombocytopenia (VITT; synonym, thrombosis with thrombocytopenia syndrome, is associated with high-titer immunoglobulin G antibodies directed against platelet factor 4 (PF4). These antibodies activate platelets via platelet FcγIIa receptors, with platelet activation greatly enhanced by PF4. Here we summarize the current concepts in the pathogenesis of VITT. We first address parallels between heparin-induced thrombocytopenia and VITT, and provide recent findings on binding of PF4 to adenovirus particles and non-assembled adenovirus proteins in the 2 adenovirus vector-based COVID-19 vaccines, ChAdOx1 nCoV-19 and Ad26.COV2.S. Further, we discuss the potential role of vaccine constituents such as glycosaminoglycans, EDTA, polysorbate 80, human cell-line proteins and nucleotides as potential binding partners of PF4. The immune response towards PF4 in VITT is likely triggered by a proinflammatory milieu. Human cell-line proteins, non-assembled virus proteins, and potentially EDTA may contribute to the proinflammatory state. The transient nature of the immune response towards PF4 in VITT makes it likely that-as in heparin-induced thrombocytopenia -marginal zone B cells are key for antibody production. Once high-titer anti-PF4 antibodies have been formed 5 to 20 days after vaccination, they activate platelets and granulocytes. Activated granulocytes undergo NETosis and the released DNA also forms complexes with PF4, which fuels the Fcγ receptor-dependent cell activation process, ultimately leading to massive thrombin generation. Finally, we summarize our initial observations indicating that VITT-like antibodies might also be present in rare patients with recurrent venous and arterial thrombotic complications, independent of vaccination.

Intracellular Reverse Transcription of Pfizer BioNTech COVID-19 mRNA Vaccine BNT162b2 In Vitro in Human Liver Cell Line

Preclinical studies of COVID-19 mRNA vaccine BNT162b2, developed by Pfizer and BioNTech, showed reversible hepatic effects in animals that received the BNT162b2 injection. Furthermore, a recent study showed that SARS-CoV-2 RNA can be reverse-transcribed and integrated into the genome of human cells. In this study, we investigated the effect of BNT162b2 on the human liver cell line Huh7 in vitro. Huh7 cells were exposed to BNT162b2, and quantitative PCR was performed on RNA extracted from the cells. We detected high levels of BNT162b2 in Huh7 cells and changes in gene expression of long interspersed nuclear element-1 (LINE-1), which is an endogenous reverse transcriptase. Immunohistochemistry using antibody binding to LINE-1 open reading frame-1 RNA-binding protein (ORFp1) on Huh7 cells treated with BNT162b2 indicated increased nucleus distribution of LINE-1. PCR on genomic DNA of Huh7 cells exposed to BNT162b2 amplified the DNA sequence unique to BNT162b2. Our results indicate a fast up-take of BNT162b2 into human liver cell line Huh7, leading to changes in LINE-1 expression and distribution. We also show that BNT162b2 mRNA is reverse transcribed intracellularly into DNA in as fast as 6 h upon BNT162b2 exposure.

Ocular Complications Following Vaccination for COVID-19: A One-Year Retrospective

Vaccination efforts as a mitigation strategy in the corona virus disease 2019 (COVID-19) pandemic are fully underway. A vital component of understanding the optimal clinical use of these vaccines is a thorough investigation of adverse events following vaccination. To date, some limited reports and reviews have discussed ocular adverse events following COVID-19 vaccination, but a systematic review detailing these reports with manifestations and clinical courses as well as proposed mechanisms has yet to be published. This comprehensive review one-year into vaccination efforts against COVID-19 is meant to furnish sound understanding for ophthalmologists and primary care physicians based on the existing body of clinical data. We discuss manifestations categorized into one of the following: eyelid, orbit, uveitis, retina, vascular, neuro-ophthalmology, ocular motility disorders, and other.

The state of complement in COVID-19

Hyperactivation of the complement and coagulation systems is recognized as part of the clinical syndrome of COVID-19. Here we review systemic complement activation and local complement activation in response to the causative virus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and their currently known relationships to hyperinflammation and thrombosis. We also provide an update on early clinical findings and emerging clinical trial evidence that suggest potential therapeutic benefit of complement inhibition in severe COVID-19.

New-onset autoimmune phenomena post COVID-19 vaccination

Coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to an unprecedented setback for global economy and health. Vaccination is one of the most effective intervention to substantially reduce severe disease and death due to SARS-CoV-2 infection. Vaccination programs are being rolled out globally, but most of these vaccines have been approved without extensive studies on their side effects and efficacy. Recently, new-onset autoimmune phenomena after COVID-19 vaccination have been reported increasingly (e.g., immune thrombotic thrombocytopenia, autoimmune liver diseases, Guillain-Barré syndrome, IgA nephropathy, rheumatoid arthritis and systemic lupus erythematosus, etc.). Molecular mimicry, the production of particular autoantibodies and the role of certain vaccine adjuvants seem to be substantial contributors to autoimmune phenomena. However, whether the association between COVID-19 vaccine and autoimmune manifestations is coincidental or causal remains to be elucidated. Here, we summarize the emerging evidence about autoimmune manifestations occurring in response to certain COVID-19 vaccines. Although information pertaining to the risk of autoimmune disease as a consequence of vaccination is controversial, we merely propose our current understanding of autoimmune manifestations associated with COVID-19 vaccine. In fact, we do not aim to disavow the overwhelming benefits of mass COVID-19 vaccination in preventing COVID-19 morbidity and mortality. These reports could help guide clinical assessment and management of autoimmune manifestations after COVID-19 vaccination.

Interactions of adenoviruses with platelets and coagulation and the vaccine-induced immune thrombotic thrombocytopenia syndrome

The COVID-19 pandemic has had a heavy impact on global health and economy and vaccination remains the primary way of controlling the infection. During the ongoing vaccination campaign some unexpected thrombotic events have emerged in subjects who had recently received the AstraZeneca (Vaxzevria) vaccine or the Johnson and Johnson (Janssen) vaccine, two adenovirus vector-based vaccines. Epidemiological studies confirm that the observed/expected ratio of these unusual thromboses is abnormally increased, especially in women in fertile age. The characteristics of this complication, with venous thromboses at unusual sites, most frequently in the cerebral vein sinuses but also in splanchnic vessels, often with multiple associated thromboses, thrombocytopenia, and sometimes disseminated intravascular coagulation, are unique and the time course and tumultuous evolution are suggestive of an acute immunological reaction. Indeed, plateletactivating anti-PF4 antibodies have been detected in a large proportion of the affected patients. Several data suggest that adenoviruses may interact with platelets, the endothelium and the blood coagulation system. Here we review interactions between adenoviral vectors and the hemostatic system that are of possible relevance in vaccine-associated thrombotic thrombocytopenia syndrome. We systematically analyze the clinical data on the reported thrombotic complications of adenovirus-based therapeutics and discuss all the current hypotheses on the mechanisms triggering this novel syndrome. Although, considering current evidence, the benefit of vaccination clearly outweighs the potential risks, it is of paramount importance to fully unravel the mechanisms leading to vaccineassociated thrombotic thrombocytopenia syndrome and to identify prognostic factors through further research.

Adenoviral vector-based platforms for developing effective vaccines to combat respiratory viral infections

Since the development of the first vaccine against smallpox over two centuries ago, vaccination strategies have been at the forefront of significantly impacting the incidences of infectious diseases globally. However, the increase in the human population, deforestation and climate change, and the rise in worldwide travel have favored the emergence of new viruses with the potential to cause pandemics. The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic is a cruel reminder of the impact of novel pathogens and the suboptimal capabilities of conventional vaccines. Therefore, there is an urgent need to develop new vaccine strategies that allow the production of billions of doses in a short duration and are broadly protective against emerging and re-emerging infectious diseases. Extensive knowledge of the molecular biology and immunology of adenoviruses (Ad) has favored Ad vectors as platforms for vaccine design. The Ad-based vaccine platform represents an attractive strategy as it induces robust humoral and cell-mediated immune responses and can meet the global demand in a pandemic situation. This review describes the status of Ad vector-based vaccines in preclinical and clinical studies for current and emerging respiratory viruses, particularly coronaviruses, influenza viruses and respiratory syncytial viruses.

Pathophysiology of Vaccine-Induced Prothrombotic Immune Thrombocytopenia (VIPIT) and Vaccine-Induced Thrombocytopenic Thrombosis (VITT) and Their Diagnostic Approach in Emergency

SARS-CoV-2 induced a pandemic that is reported to have started in Asia and was then extended to other countries in the world. Main clinical aspects of this viral infection have been lung injuries with severe pneumonia requiring prolonged hospitalization and associated morbidities such as venous thromboembolism and/or superinfection by bacteria, fungus or other pests. Immediately there was a need to develop a sustainable therapeutic strategy, such as vaccination. Vaccines against Covid-19, in fact, exert a protective action for common people and reduce viral diffusion. Yet, vaccination of a large number of people raises the question of a well-known complication of several types of vaccines; this complication is immune thrombocytopenia, which is sometimes associated with thrombosis as well. In this short review, we summarized mechanisms involved in the pathogenesis of vaccine-induced prothrombotic immune thrombocytopenia and vaccine-induced thrombocytopenic thrombosis.

The Emergency Use Authorization of Pharmaceuticals: History and Utility During the COVID-19 Pandemic

The Emergency Use Authorization (EUA) originated in 2004 because of the need for emergency medical countermeasures (MCMs) against potential bioterrorist attacks. The EUA also proved useful in dealing with subsequent pandemics and has emerged as a critical regulatory pathway for therapeutics and vaccines throughout the Coronavirus Disease 2019 (COVID-19) pandemic. With the EUA process in the USA, we witnessed emergency authorizations, their expansions, as well as withdrawal of previously authorized products, which exemplifies the dynamic nature of scientific review of EUA products. EUAs proved vital for the first group of COVID-19 vaccines, including the temporary pause of one vaccine while emergency safety issues were evaluated. Although this review on the EUA is primarily focused on the USA, distinctions were made with other jurisdictions such as Europe and Canada with respect to the emergency authorizations of the vaccines. Finally, we discuss some important differences following EUA and formal new drug/vaccine application (NDA/BLA) approvals.