Vaccination against COVID-19: insight from arterial and venous thrombosis occurrence using data from VigiBase

Arterial Thrombosis in an Unusual Site (Ulnar Artery) after COVID-19 Vaccination-A Case Report

Spontaneous events have been reported after COVID-19 vaccination. In this case, we report a thrombotic event in an unusual site (ulnar artery) after COVID-19 vaccination. The patient (69 year-old-male) had no changes after a laboratory investigation regarding thrombophilic pattern, but nevertheless had atherothrombotic predisposing conditions. Arterial thrombotic events have more frequently been reported after mRNA vaccines than after adenovirus vaccines. This is the first case reported of thrombosis of the ulnar artery occurring in the same side of the body where the vaccination took place. However, it must be noted that COVID-19 vaccines cumulatively offer a net positive effect, despite rare adverse effects.

Cerebral venous sinus thrombosis in the setting of COVID-19 vaccination: a systematic review and meta-analysis

Background and Purpose

Cerebral venous sinus thrombosis (CVST) has been reported as a rare adverse event in association with thrombosis-thrombocytopenia syndrome (TTS) following COVID-19 vaccination.

Methods

 We performed a systematic review and meta-analysis of investigator-initiated registries including confirmed CVST cases, with the aim to calculate (1) the odds ratio of TTS–CVST versus non-TTS–CVST after vector-based vaccines and (2) after non-vector-based vaccines, (3) the in-hospital mortality ratio of TTS–CVST compared to non-TTS–CVST; and (4) the dependency or death at discharge among TTS–CVST compared to non-TTS–CVST cases.

Results

Two eligible studies were included in the meta-analysis, comprising a total of 211 patients with CVST associated with COVID-19 vaccination. Vector-based COVID-19 vaccination was associated with a higher likelihood of TTS-associated CVST than with non-TTS–CVST (OR: 52.34, 95% CI 9.58–285.98). TTS–CVST was also associated with higher likelihood of in-hospital mortality (OR: 13.29; 95% CI 3.96–44.60) and death or dependency at discharge compared to non-TTS–CVST (OR: 6.70; 95% CI 3.15–14.26). TTS–CVST was recorded with a shorter interval between vaccination and symptom onset [Mean Difference (MD):-6.54 days; 95% CI − 12.64 to − 0.45], affecting younger patients (MD:-9.00 years; 95% CI − 14.02 to − 3.99) without risk factors for thromboses (OR:2.34; 95% CI 1.26–4.33), and was complicated more frequently with intracerebral hemorrhage (OR:3.60; 95% CI 1.31–9.87) and concomitant thromboses in other sites (OR:11.85; 95% CI 3.51–39.98) compared to non-TTS–CVST cases.

Conclusions

TTS–CVST following COVID-19 vaccination has distinct risk factor profile, clinical phenotype and prognosis compared to non-TTS–CVST. Further epidemiological data are required to evaluate the impact of different treatment strategies on outcome of TTS–CVST cases following COVID-19 vaccination.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-022-11101-2.

A Three-Case Series of Thrombotic Deaths in Patients over 50 with Comorbidities Temporally after modRNA COVID-19 Vaccination

Coronavirus disease 2019 (COVID-19) is the most dramatic pandemic of the new millennium; to counteract it, specific vaccines have been launched in record time under emergency use authorization or conditional marketing authorization by virtue of a favorable risk/benefit balance. Among the various technological platforms, there is that exploiting a nucleoside-modified messenger RNA (modRNA), such as Comirnaty^®, and that which is adenoviral vector-based. In the ongoing pharmacovigilance, the product information of the latter has been updated about the risk of thrombotic thrombocytopenia, venous thromboembolism without thrombocytopenia and immune thrombocytopenia without thrombosis. However, from an in-depth literature review, the same adverse events can rarely occur with modRNA vaccines too. In support of this, we here report a three-case series of thrombotic deaths in patients over 50 with comorbidities temporally after Comirnaty^®, investigated by means of post-mortem histopathology and immunohistochemistry. In two out of three cases, the cause of death is traced back to pulmonary microthromboses rich in activated platelets, quite similar morphologically to those described in patients who died from severe COVID-19. Even if remote in the face of millions of administered doses, clinicians should be aware of the possible thrombotic risk also after Comirnaty^®, in order to avoid a misdiagnosis with potentially lethal consequences. Since COVID-19 vaccines are inoculated in subjects to be protected, maximum attention must be paid to their safety, and prophylactic measures to increase it are always welcome. In light of the evidence, the product information of modRNA COVID-19 vaccines should be updated about the thrombotic risk, as happened for adenoviral vector-based vaccines.

Stroke Associated with COVID-19 Vaccines

Objectives

Development of safe and effective vaccines against coronavirus disease 2019 (COVID-19) remains the cornerstone of controlling this pandemic. However, there are increasing reports of various types of stroke including ischemic stroke, and hemorrhagic stroke, as well as cerebral venous sinus thrombosis (CVST) after COVID-19 vaccination. This paper aims to review reports of stroke associated with COVID-19 vaccines and provide a coherent clinical picture of this condition.

Materials and methods

A literature review was performed with a focus on data from recent studies.

Results

Most of such patients are women under 60 years of age and who had received ChAdOx1 nCoV-19 vaccine. Most studies reported CVST with or without secondary ischemic or hemorrhagic stroke, and some with Vaccine-induced Thrombotic Thrombocytopenia (VITT). The most common clinical symptom of CVST seen after COVID-19 vaccination was headache. The clinical course of CVST after COVID-19 vaccination may be more severe than CVST not associated with COVID vaccination. Management of CVST following COVID-19 vaccination is challenging and may differ from the standard treatment of CVST. Low molecular weight heparin is commonly used in the treatment of CVST; however, it may worsen outcomes in CVST associated with VITT. Furthermore, administration of intravenous immunoglobulin and high-dose glucocorticoids have been recommended with various success rates.

Conclusion

These contradictory observations are a source of confusion in clinical decision-making and warrant further study and development of clinical guidelines. Clinicians should be aware of clinical presentation, diagnosis, and management of stroke associated with COVID-19 vaccination.

Central retinal artery occlusion following COVID-19 vaccine administration

Introduction

Increased risk of thromboembolic events has been associated with SARS-CoV-2 infections and more recently, with COVID-19 vaccination. To date, however, there are no reports of an association between the COVID-19 vaccination and retinal artery occlusions. We report a case of a patient who developed central retinal artery occlusion (CRAO) 2 days following the administration of the AstraZeneca COVID-19 vaccine.

Case description

A 76-year-old woman presented to our Department of Ophthalmology complaining of painless vision loss in her left eye 48 hours after she had received her first dose of the AstraZeneca COVID-19 vaccine. Her best-corrected visual acuity was only hand movement in the left eye. Left eye ophthalmologic examination showed the presence of arterial narrowing and a cherry red spot. Optical coherence tomography showed severe macular swelling of the inner retinal layers in the left eye Fluorescein angiography performed the following day confirmed the diagnosis. The cardiovascular examination including Holter ECG was unremarkable. Complete blood count was within normal limits, without thrombocytopenia. A subsequent cerebral CT and CT-angiography scans did not show any other acute vascular event. Doppler angiography of the carotid artery was performed and showed normal flow without clinically significant plaques, stenoses, occlusions or dissections.

Conclusions

To our knowledge, this is the first case of an isolated CRAO following the administration of the AstraZeneca COVID-19 vaccine. Further studies are needed to evaluate this potential association and identify pathophysiologic relationships between COVID-19 vaccinations and CRAO.

COVID-19, Vaccines, and Thrombotic Events: A Narrative Review

The coronavirus disease 2019 (COVID-19), a deadly pandemic that has affected millions of people worldwide, is associated with cardiovascular complications, including venous and arterial thromboembolic events. Viral spike proteins, in fact, may promote the release of prothrombotic and inflammatory mediators. Vaccines, coding for the spike protein, are the primary means for preventing COVID-19. However, some unexpected thrombotic events at unusual sites, most frequently located in the cerebral venous sinus but also splanchnic, with associated thrombocytopenia, have emerged in subjects who received adenovirus-based vaccines, especially in fertile women. This clinical entity was soon recognized as a new syndrome, named vaccine-induced immune thrombotic thrombocytopenia, probably caused by cross-reacting anti-platelet factor-4 antibodies activating platelets. For this reason, the regulatory agencies of various countries restricted the use of adenovirus-based vaccines to some age groups. The prevailing opinion of most experts, however, is that the risk of developing COVID-19, including thrombotic complications, clearly outweighs this potential risk. This point-of-view aims at providing a narrative review of epidemiological issues, clinical data, and pathogenetic hypotheses of thrombosis linked to both COVID-19 and its vaccines, helping medical practitioners to offer up-to-date and evidence-based counseling to their often-alarmed patients with acute or chronic cardiovascular thrombotic events.

SARS-CoV-2-related and Covid-19 vaccine-induced thromboembolic events: A comparative review

Since the start of the pandemic, thrombotic events have been a well-known and severe complication associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Nevertheless, the initiation of vaccination programs brought another rare yet highly fatal thrombotic event, vaccine-induced immune thrombotic thrombocytopaenia, which has caused extensive debate regarding the safety of vaccines. This review defines the thromboembolic events following infection and vaccination, identifies their risk factors, describes their pathophysiology, and discusses their management, treatment, and prevention.

Frequency and Associations of Adverse Reactions of COVID-19 Vaccines Reported to Pharmacovigilance Systems in the European Union and the United States

Introduction

This study aims to provide a risk assessment of the adverse reactions related to the COVID-19 vaccines manufactured by AstraZeneca, Janssen, Moderna, and Pfizer-BioNTech which have been in use in the European Union and the United States between December 2020 and October 2021.

Methods

Data from the European Database of Suspected Adverse Drug Reaction (EudraVigilance) and the Vaccine Adverse Events Reporting System (VAERS) from 2020 to October 2021 are analysed. More than 7.8 million adverse reactions of about 1.6 million persons are included. The adverse reactions are classified with the Common Toxicity Criteria (CTC) categories. COVID-19 vaccine exposures and adverse reactions reported between December 2020 and October 2021 are compared to influenza vaccine exposures and adverse reactions reported between 2020 and 2021. The population-level vaccine exposures to COVID-19 and influenza vaccines comprised about 451 million and 437 million exposures, respectively. Absolute and relative risk estimates are calculated by CTC categories and COVID-19 vaccines for the EU and US populations aged 18 years and older.

Results

A higher risk of reporting serious adverse reactions was observed for the COVID-19 vaccines in comparison to the influenza vaccines. Individuals age 65 and older were associated with a higher frequency of death, hospitalisations, and life-threatening reactions than younger individuals (relative risk estimates between 1.49 99% CI [1.44–1.55] and 8.61 99% CI [8.02–9.23]). Outcome onset of serious adverse reactions occurred within the first 7 days after vaccination in about 77.6–89.1% of cases. The largest absolute risks were observed for allergic, constitutional reactions, dermatological, gastrointestinal, neurological reactions, and localised and non-localised pain. The largest relative risks between COVID-19 vs. influenza vaccines were observed for allergic reactions, arrhythmia, general cardiovascular events, coagulation, haemorrhages, gastrointestinal, ocular, sexual organs reactions, and thrombosis.

Conclusion

The present study provides an overview of adverse reactions frequently reported to the pharmacovigilance systems following COVID-19 vaccination in the EU and US populations. Despite the limitations of passive reporting systems, these results may inform further clinical research investigating in more detail the pathophysiological mechanisms potentially associated with the COVID-19 vaccines.

Cerebral Venous Sinus Thrombosis following COVID-19 Vaccination: Analysis of 552 Worldwide Cases

To date, billions of vaccine doses have been administered to restrain the current COVID-19 pandemic worldwide. Rare side effects, including intravascular blood clots, were reported in the general population after vaccination. Among these, cerebral venous sinus thrombosis (CVST) has been considered the most serious one. To shed further light on such an event, we conducted a literature search for case descriptions of CVST in vaccinated people. Findings were analyzed with emphasis on demographic characteristics, type of vaccine, site of thrombosis, clinical and histopathological findings. From 258 potential articles published till September 2021, 41 studies were retrieved for a total of 552 patients. Of these, 492 patients (89.1%) had received AZD1222/Vaxzevria, 45 (8.2%) BNT162b2/CX-024414 Spikevax, 15 (2.7%) JNJ-78436735, and 2 (0.3%) Covishield vaccine. CVST occurred in 382 women and 170 men (mean aged 44 years), and the median timing from the shot was 9 days (range 2-45). Thrombi were predominantly seen in transverse (84%), sigmoid (66%), and/or superior sagittal (56%) sinuses. Brain injury (chiefly intracranial bleeding) occurred in 32% of cases. Of 426 patients with detailed clinical course, 63% were discharged in good clinical conditions, at times with variable neurological sequelae, whereas 37% deceased, largely due to brain injury. This narrative review confirmed CVST as a rare event after (adenoviral vector) COVID-19 vaccination, with a women/men rate ratio of 2.25. Though the pathogenesis of thrombosis is still under discussion, currently available histopathological findings likely indicate an underlying immune vasculitis.

Cardiovascular and haematological events post COVID-19 vaccination: A systematic review

Since COVID-19 took a strong hold around the globe causing considerable morbidity and mortality, a lot of effort was dedicated to manufacturing effective vaccines against SARS-CoV-2. Many questions have since been raised surrounding the safety of the vaccines, and a lot of media attention to certain side effects. This caused a state of vaccine hesitancy that may prove problematic in the global effort to control the virus. This review was undertaken with the aim of putting together all the reported cardiovascular and haematological events post COVID-19 vaccination in published literature and to suggest possible mechanisms to explain these rare phenomena.

The Variation of SARS-CoV-2 and Advanced Research on Current Vaccines

Over the past 2 years, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the coronavirus disease 2019 (COVID-19) and rapidly spread worldwide. In the process of evolution, new mutations of SARS-CoV-2 began to appear to be more adaptable to the diverse changes of various cellular environments and hosts. Generally, the emerging SARS-CoV-2 variants are characterized by high infectivity, augmented virulence, and fast transmissibility, posing a serious threat to the prevention and control of the global epidemic. At present, there is a paucity of effective measurements to cure COVID-19. It is extremely crucial to develop vaccines against SARS-CoV-2 and emerging variants to enhance individual immunity, but it is not yet known whether they are approved by the authority. Therefore, we systematically reviewed the main characteristics of the emerging various variants of SARS-CoV-2, including their distribution, mutations, transmissibility, severity, and susceptibility to immune responses, especially the Delta variant and the new emerging Omicron variant. Furthermore, we overviewed the suitable crowd, the efficacy, and adverse events (AEs) of current vaccines.

Venous Thrombosis within 30 Days after Vaccination against SARS-CoV-2 in a Multinational Venous Thromboembolism Registry

Background: Venous thromboembolism (VTE)—including deep vein thrombosis, pulmonary embolism, and cerebral venous sinus thrombosis (CVST)—may occur early after vaccination against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We sought to describe the site, clinical characteristics, and outcomes of VTE after vaccination against SARS-CoV-2. Methods: In a prospective study using the Registro Informatizado de Enfermedad TromboEmbólica (RIETE) platform, patients with VTE 4–30 days after vaccination against SARS-CoV-2 (1 February 2021 through 30 April 2021) were included. VTE patients recruited from the same centers into RIETE in the same months in 2018–2019 were selected as the reference group. All-cause mortality and major bleeding were the main study outcomes. Results: As of 30 April 2020, 102 patients with post-vaccination VTEs had been identified (28 after adenovirus-based vaccination [ChAdOx1 nCov-19; AstraZeneca] and 74 after mRNA-based vaccination [mRNA-1273; Moderna, and BNT162b2; Pfizer]). Compared with 911 historical controls, patients with VTE after adenovirus-based vaccination more frequently had CVST (10.7% vs. 0.4%, p < 0.001) or thrombosis at multiple sites (17.9% vs. 1.3%, p < 0.001), more frequently had thrombocytopenia (40.7% vs. 14.7%, p < 0.001), and had higher 14-day mortality (14.3% vs. 0.7%; odds ratio [OR]: 25.1; 95% confidence interval [CI]: 6.7–94.9) and major bleeding rates (10.3% vs. 1.0%, OR: 12.03, 95% CI: 3.07–47.13). The site of thrombosis, accompanying thrombocytopenia, and 14-day mortality rates were not significantly different for patients with VTE after mRNA-based vaccination, compared with historical controls. Conclusions: Compared with historical controls, VTE after adenovirus-based vaccination against SARS-CoV-2 is accompanied by thrombocytopenia, occurs in unusual sites, and is associated with worse clinical outcomes.

Isolated thrombosis after COVID-19 vaccination: case series

Background

Data regarding thrombosis after COVID-19 vaccination are scarce.

Methods

Clinical and laboratory data were collected from all patients who developed thrombosis within 4 weeks of receiving the Pfizer or Oxford/AstraZeneca vaccine. None had a COVID-19-positive swab.

Results

Seventeen patients were included, with average age of 48.8 years and equal proportion of females to males. Our data suggest that thrombosis occurred in 1 in 163,000 of all individuals who had received any dose of any type of COVID-19 vaccine: six (1 in 123,000) patients after the first dose of Oxford/AstraZeneca, none after the second dose of Oxford/AstraZeneca, four (1 in 257,000) patients after the first dose of the Pfizer vaccine, and seven (1 in 102,000) patients after the second dose of Pfizer vaccine. Three of 17 patients with thrombosis (17.6%) died.

Conclusions

We believe this report to be one of the earliest in the literature to address the question of whether isolated thrombosis is a possible complication of COVID-19 vaccination.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12185-021-03285-6.

Acute Ischemic Stroke in the Context of SARS-CoV-2 Vaccination: A Systematic Review

BACKGROUND

There have been reports suggesting an increased incidence of acute ischemic stroke among anti-SARS-CoV-2 vaccinees. We aimed to systematically review the literature to summarize the available evidence on the association between SARS-CoV-2 vaccination and acute ischemic stroke.

METHODS

A systematic literature search on MEDLINE, LitCovid and LIVIVO databases was performed for eligible randomized controlled trials, observational studies, registries and case reports that reported on imaging-confirmed acute ischemic stroke in the context of any SARS-CoV-2 vaccination with BNT162b2, mRNA-1273, Ad26.COV2.S, ChAdOx1 or Gam-COVID-Vac. Literature search was limited to English and German languages and publication date before October 19, 2021.

RESULTS

We identified a total of 395,105,670 individuals who underwent vaccination. We found 21 sources, including 2 cohort studies, 4 registry studies, 3 randomized clinical trials, and 12 case reports. Individuals included in these studies were at least 16 years old. Cari et al observed a higher likelihood of acute ischemic stroke in vaccinees aged 18-64 years, compared to Whiteley et al observing vaccinees older than 70 years when vaccinated. In addition, differences in the likelihood of acute ischemic stroke were found among the vaccines studied, although no overall increased stroke incidence was demonstrated with vaccination.

CONCLUSION

In this systematic review of the available literature, we found that the risk of acute ischemic stroke does not appear to be increased in vaccinated individuals who have received any of the currently licensed SARS-CoV-2 vaccines compared with the baseline incidence of stroke.

Exacerbation of branch retinal vein occlusion post SARS-CoV2 vaccination: Case reports

RATIONALE

In this paper, we report on 2 patients who developed branch retinal vein occlusion (BRVO) exacerbation 1 day after administration of the BNT162b2 (Pfizer-BioNTech) SARS-CoV-2 vaccine.

PATIENT CONCERNS

Case 1: A 71 year-old female developed vision loss in her left eye 1 day after receiving a second dose of the SARS-CoV-2 mRNA vaccine. This patient was diagnosed with temporal inferior BRVO and secondary macular edema (ME) in her left eye. ME resolved after 3 doses of intravitreal aflibercept (IVA). After treatment, no recurrence of ME was observed.Case 2: A 72 year-old man developed vision loss in his right eye 1 day after receiving the first dose of the SARS-CoV-2 mRNA vaccine. This patient was diagnosed with temporal superior BRVO in the right eye without ME. The patient was followed up and did not undergo any additional treatment.

DIAGNOSES

Case1: Temporal superior BRVO and secondary ME were observed in the left eye. Her best-corrected visual acuity (BCVA) was 20/30.Case2: Temporal superior BRVO recurrence and secondary ME were observed in the right eye. BCVA was 20/25.

INTERVENTIONS

Case1: Additional dose of IVA was administered. Case2: Two times of Intravitreal ranibizumab was administered twice.

OUTCOMES

Case1: Subsequently, ME resolved BCVA was 20/20. Case2: Subsequently, ME resolved BCVA was 20/25.

LESSONS

Both cases showed a possible association between SARS-CoV-2 vaccination and the exacerbation of BRVO.

COVID-19 vaccination in adults with congenital heart disease: Real-world data from an Italian tertiary centre

Background

real-world data on COVID-19 vaccine safety, immunogenicity and acceptance in adults with congenital heart disease (ACHD) are lacking.

Methods

ACHD patients who were offered COVID-19 vaccination from January to June 2021 were included. Data on adverse events, on patients' attitude towards vaccination and antispike IgG titre were retrospectively collected. A group of healthy individuals with similar age and sex undergoing vaccination was included for comparison.

Results

208 patients followed in a single ACHD tertiary centre (33.3 [26-45] years, 54% male) received COVID-19 vaccine, 65% vaccinated at our institution: 199 (96%) received Pfizer-BioNTech BNT162b2 vaccine, 4 (2%) Moderna-1273 and 5 (2%) AstraZeneca-ChAdOx1. Median follow-up after vaccination was 79 [57-96] days. No major adverse event was reported and the incidence of minor events was not different between ACHD patients and the control group. One patient was diagnosed with acute pericarditis. There were two deaths unrelated to the vaccine during follow-up. Three (1.5%) vaccinated patients tested positive for COVID-19. Antispike IgG titre, available in 159 (76%) patients, was 1334 [600-3401] BAU/ml, not significantly different from the control group (p=0.2). One patient with Fontan failure was seronegative. Advanced physiological stage was associated with lower antibody response, independently from previous viral exposure (p<0.0001). Fourteen percent refused COVID-19 vaccination at our institution. However, 50% of vaccinated patients declared to have been influenced by the discussion with the ACHD cardiologist and 66% of those vaccinated in situ reported that undergoing COVID-19 vaccination at the ACHD centre made them feel safer.

Conclusion

COVID-19 vaccines appear safe in ACHD with satisfactory immunogenicity. However, the most vulnerable patients showed lower antibody response. ACHD team may play a key role in vaccine acceptance.

Cerebral venous sinus thrombosis (CVST) associated with SARS-CoV-2 vaccines: clues for an immunopathogenesis common to CVST observed in COVID-19

Severe acute respiratory syndrome coronavirus type 2 has been responsible for an unprecedented pandemic, and nowadays, several vaccines proved to be effective and safe, representing the only available strategy to stop the pandemic. While millions of people have safely received vaccine, rare and unusual thrombotic events have been reported and are undergoing investigations to elucidate their nature. Understanding initial trigger, underlying pathophysiology and the reasons for specific site localization of thrombotic events are a matter of debate.

We here propose that rare cases of cerebral venous sinus thrombosis, a clinical event that may rapidly evolve to brain death, reported after COVID-19 vaccine, might be consequent to an immune response resulting in inflamed/damaged endothelium, an event similar to that described for cases of cerebral venous sinus thrombosis reported during COVID-19 and not necessarily related to anti-Platelets Factor 4 antibodies, as recently described. Remarkably, in the two patients presenting at our hospital with cerebral venous sinus thrombosis and evolved to brain death, proper tissue perfusion and function maintenance allowed organ donation despite extensive thrombosis in the organ donors, with favorable outcome at 6 months.

Increased vigilance, close multidisciplinary collaboration, and further prospective research will help to better elucidate a very rare and still not fully understood pathophysiological event associated with vaccines for severe acute respiratory syndrome coronavirus 2.

Neurological symptoms and neuroimaging alterations related with COVID-19 vaccine: Cause or coincidence?

Although vaccination against Coronavirus disease-2019 (COVID-19) is still occurring, several adverse effects temporally related to these vaccines are already being reported, even if through isolated case reports. In the present study, we describe the lesions seen on magnetic resonance imaging (MRI) of three patients who developed neurological symptoms after receiving the ChAdOX1 nCoV-19 vaccine (Oxford/AstraZeneca). The first patient presented with an ischemic stroke in the posterior limb of the left internal capsule, two days after vaccination. The second patient presented with a left facial nerve palsy, seven days after vaccination. The third patient presented with myelitis, eight days after receiving the vaccine. All patients presented the symptoms after the first dose of the vaccine and did not have a history of previous COVID-19. The real incidence of these types of complications is not known yet, but it is important to consider the possibility of COVID-19 vaccine complications, in patients with a recent history of vaccination and recent development of neurological symptoms, even though this association is only casual. Longitudinal studies are necessary to further analyze the incidence of the adverse effects of each vaccine against SARS-CoV-2.

Cerebral Venous Sinus Thrombosis and Thrombotic Events After Vector-Based COVID-19 Vaccines: A Systematic Review and Meta-analysis

BACKGROUND AND OBJECTIVES

There is accumulating evidence supporting an association between the thrombosis and thrombocytopenia syndrome (TTS) and adenovirus vector-based vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Yet TTS and TTS-associated cerebral venous sinus thrombosis (CVST) remain poorly characterized. We aim to systematically evaluate the proportion of CVST among TTS cases and assess its characteristics and outcomes.

METHODS

We performed a systematic review and meta-analysis of clinical trials, cohorts, case series, and registry-based studies with the aim to assess (1) the pooled mortality rate of CVST, TTS-associated CVST, and TTS and (2) the pooled proportion of patients with CVST among patients with any thrombotic event and TTS. Secondary outcomes comprised clinical characteristics of patients with postvaccination thrombotic event. This meta-analysis is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and was written according to the Meta-analysis of Observational Studies in Epidemiology proposal.

RESULTS

Sixty-nine studies were included in the qualitative analysis comprising 370 patients with CVST out of 4,182 patients with any thrombotic event associated with SARS-CoV-2 vector-based vaccine administration. Twenty-three studies were included further in quantitative meta-analysis. Among TTS cases, the pooled proportion of CVST was 51% (95% confidence interval [CI] 36%-66%; I ² = 61%). TTS was independently associated with a higher likelihood of CVST when compared to patients without TTS with thrombotic events after vaccination (odds ratio 13.8; 95% CI 2.0-97.3; I ² = 78%). The pooled mortality rates of TTS and TTS-associated CVST were 28% (95% CI 21%-36%) and 38% (95% CI 27%-49%), respectively. Thrombotic complications developed within 2 weeks of exposure to vector-based SARS-CoV-2 vaccines (mean interval 10 days; 95% CI 8-12) and affected predominantly women (69%; 95% CI 60%-77%) under age 45, even in the absence of prothrombotic risk factors.

DISCUSSION

Approximately half of patients with TTS present with CVST; almost one-third of patients with TTS do not survive. Further research is required to identify independent predictors of TTS following adenovirus vector-based vaccination.

REGISTRATION INFORMATION

The prespecified study protocol has been registered in the International Prospective Register of Ongoing Systematic Reviews PROSPERO (CRD42021250709).

Cerebral Venous Sinus Thrombosis After BNT162b2 mRNA COVID-19 Vaccination

W present a rare case of cerebral venous sinus thrombosis after the BNT162b2 mRNA COVID-19 vaccine. A 61-year-old Japanese man developed a headache 10 days after the first dose of the vaccine. Magnetic resonance venography and contrast-enhanced brain MRI showed thrombosis in the superior sagittal sinus and the right transverse sinus. Anticoagulation with intravenous unfractionated heparin followed by oral warfarin was started. His headache improved, and brain MRI on day 22 showed resolution of thrombus. He was maintained on anticoagulation with warfarin and discharged without any neurological sequelae. This case is presented in the context of the relevant literature.

Comparison of the Results of Five SARS-CoV-2 Antibody Assays before and after the First and Second ChAdOx1 nCoV-19 Vaccinations among Health Care Workers: a Prospective Multicenter Study

Reliable results for serological positivity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody after the second dose of AstraZeneca (AZ) vaccination are important to estimate the real efficacy of vaccination. We evaluated positivity rates and changes in semiquantitative antibody titers before and after the first and second ChAdOx1 nCoV-19 vaccinations using five SARS-CoV-2 antibody assays, including two surrogate virus neutralization tests. A total of 674 serum samples were obtained from 228 participants during three blood sampling periods. A questionnaire on symptoms, severity, and adverse reaction duration was completed by participants after the second vaccination. The overall positive rates for all assays were 0.0 to 0.9% before vaccination, 66.2 to 92.5% after the first vaccination, and 98.2 to 100.0% after the second vaccination. Median antibody titers in five assays after the second dose of vaccination were increased compared to those after the first dose (106.4-fold increase for Roche total antibody, 3.6-fold for Abbott IgG, 3.6-fold for Siemens, 1.2-fold for SD Biosensor V1 neutralizing antibody, and 2.2-fold for GenScript neutralizing antibody). Adverse reactions were reduced after the second dose in 89.9% of participants compared to after the first dose. Overall, the second vaccination led to almost 100% positivity rates based on these SARS-CoV-2 antibody assays. The results should be interpreted with caution, considering the characteristics of the applied assays. Our findings could inform decisions regarding vaccination and the use of immunoassays, thus contributing to SARS-CoV-2 pandemic control.

Retinal Vascular Events after mRNA and Adenoviral-Vectored COVID-19 Vaccines-A Case Series

Background: To describe cases of retinal vascular events shortly after administration of mRNA or adenoviral-vectored COVID-19 vaccines. Design: Retrospective, multicenter case series. Methods: Six cases of retinal vascular events shortly after receiving COVID-19 vaccines. Results: A 38-year-old, otherwise healthy male patient presented with branch retinal arterial occlusion four days after receiving his second dose of SARS-CoV-2 vaccination with Comirnaty^® (BioNTech^®, Mainz, Germany; Pfizer^®, New York City, NY, USA). An 81-year-old female patient developed visual symptoms twelve days after the second dose of SARS-CoV-2 vaccination with Comirnaty^® and was diagnosed with a combined arterial and venous occlusion in her right eye. A 40-year-old male patient noticed blurry vision five days after his first dose of SARS-CoV-2 vaccination with Comirnaty^® and was diagnosed with venous stasis retinopathy in his left eye. A 67-year-old male was diagnosed with non-arteritic anterior ischemic optic neuropathy in his right eye four days after receiving the first dose of Vaxzevria^® (AstraZeneca^®, Cambridge, UK). A 32-year-old man presented with a sudden onset of a scotoma two days after receiving the second dose of SARS-CoV-2 vaccination with Spikevax^® (Moderna, Cambridge, UK) and was diagnosed with a circumscribed nerve fiber infarction. A 21-year-old female patient developed an acute bilateral acute macular neuroretinopathy three days after receiving the first dose of SARS-CoV2-vaccine Vaxzevria^® (AstraZeneca^®, Cambridge, UK). Conclusion: This case series describes six cases of retinal vascular events shortly after receiving mRNA or adenoviral-vectored COVID-19 vaccines. The short time span between received vaccination and occurrence of the observed retinal vascular events raises the question of a direct correlation. Our case series adds to further reports of possible side effects with potential serious post-immunization complications of COVID-19 vaccinations.

Thrombotic Adverse Events Reported for Moderna, Pfizer and Oxford-AstraZeneca COVID-19 Vaccines: Comparison of Occurrence and Clinical Outcomes in the EudraVigilance Database

Vaccination against COVID-19 is the cornerstone of controlling and mitigating the ongoing pandemic. Thrombotic adverse events linked to Moderna, Pfizer and the Oxford-AstraZeneca vaccine have been documented and described as extremely rare. While the Oxford-AstraZeneca vaccine has received much of the attention, the other vaccines should not go unchallenged. This study aimed to determine the frequency of reported thrombotic adverse events and clinical outcomes for these three COVID-19 vaccines, namely, Moderna, Pfizer and Oxford-AstraZeneca. A retrospective descriptive analysis was conducted of spontaneous reports for Moderna, Pfizer and Oxford-AstraZeneca COVID-19 vaccines submitted to the EudraVigilance database in the period from 17 February to 14 June 2021. There were 729,496 adverse events for the three vaccines, of which 3420 were thrombotic, mainly Oxford-AstraZeneca (n = 1988; 58.1%) followed by Pfizer (n = 1096; 32.0%) and Moderna (n = 336; 9.8%). As serious adverse events, there were 705 reports of pulmonary embolism for the three vaccines, of which 130 reports (18.4%) were for Moderna, 226 reports (32.1%) for Pfizer and 349 (49.5%) for Oxford-AstraZeneca vaccines. The occurrence of pulmonary embolism is significantly associated with a fatal outcome (p ≤ 0.001). Sixty-three fatalities were recorded (n = 63/3420; 1.8%), of which Moderna (n = 6), Pfizer (n = 25) and Oxford-AstraZeneca (n = 32).

Hospital-based observational study of neurological disorders in patients recently vaccinated with COVID-19 mRNA vaccines

PURPOSE

We describe the spectrum of acute neurological disorders among hospitalized patients who recently had COVID-19 mRNA vaccination.

METHOD

We performed a prospective study at 7 acute hospitals in Singapore. Hospitalized patients who were referred for neurological complaints and had COVID-19 mRNA vaccines, BNT162b2 and mRNA-1273, in the last 6 weeks were classified into central nervous system (CNS) syndromes, cerebrovascular disorders, peripheral nervous system (PNS) disorders, autonomic nervous system (ANS) disorders and immunization stress-related responses (ISRR).

RESULTS

From 30 December 2020 to 20 April 2021, 1,398,074 persons (median age 59 years, 54.5% males) received COVID-19 mRNA vaccine (86.7% BNT162b2, 13.3% mRNA-1273); 915,344(65.5%) completed 2 doses. Four hundred and fifty-seven(0.03%) patients were referred for neurological complaints [median age 67(20-97) years, 281(61.5%) males; 95.8% received BNT162b2 and 4.2% mRNA-1273], classified into 73(16.0%) CNS syndromes, 286(62.6%) cerebrovascular disorders, 59(12.9%) PNS disorders, 0 ANS disorders and 39(8.5%) ISRRs. Eleven of 27 patients with cranial mononeuropathy had Bell's palsy. Of 33 patients with seizures, only 4 were unprovoked and occurred within 2 weeks of vaccination. All strokes occurred among individuals with pre-existing cardiovascular risk factors. We recorded 2 cases of cerebral venous thrombosis; none were vaccine-induced thrombotic thrombocytopenia. Five had mild flares of immune-mediated diseases.

CONCLUSION

Our observational study does not establish causality of the described disorders to vaccines. Though limited by the lack of baseline incidence data of several conditions, we observed no obvious signal of serious neurological morbidity associated with mRNA vaccination. The benefits of COVID-19 vaccination outweigh concerns over neurological adverse events.

Autoimmunity roots of the thrombotic events after COVID-19 vaccination

Although vaccination represents the most promising way to stop or contain the coronavirus disease 2019 (COVID-19) pandemic and safety and effectiveness of available vaccines were proven, a small number of individuals who received anti-SARS-CoV-2 vaccines developed a prothrombotic syndrome. Vaccine-induced immune thrombotic thrombocytopenia (VITT) can be triggered by the adenoviral vector-based vaccine, whereas lipid nanoparticle-mRNA-based vaccines can induce rare cases of deep vein thrombosis (DVT). Although the main pathogenic mechanisms behind this rare phenomenon have not yet been identified, both host and vaccine factors might be involved, with pathology at least in part being related to the vaccine-triggered autoimmune reaction. In this review, we are considering some aspects related to pathogenesis, major risk factors, as well as peculiarities of diagnosis and treatment of this rare condition.

Coronavirus and cardiovascular manifestations- getting to the heart of the matter

Coronavirus disease has unarguably been the largest pandemic of recent times. Over 150 million cases have occurred worldwide, and more than 3 million have succumbed to the disease. Cardiac manifestations can have varied presentations from an asymptomatic troponin rise to fulminant myocarditis. The pathogenesis of myocardial damage could be direct or indirect, including inflammation, coronary spasm, plaque rupture, and cytokine storm. Thromboembolism is also an important feature of cardiovascular affliction with both arterial and venous systems being affected. Hence, anticoagulation has also been a matter of debate. Fulminant myocarditis is the most severe form and can lead to circulatory shock with a high mortality. Management of cardiac patients with coronavirus disease 2019 (COVID-19) infection is not considerably different from non-COVID-19 cardiovascular disease, but interaction between cardiovascular drugs and anti-COVID-19 therapy requires careful attention. More recently, vaccines have emerged as a ray of hope for the disease. But simultaneously, there have been reports of thromboembolism following vaccination. In this review, we discuss the various aspects of coronavirus disease affecting of heart and its management.

Cerebral venous thrombosis after vaccination against COVID-19 in the UK: a multicentre cohort study

BACKGROUND

A new syndrome of vaccine-induced immune thrombotic thrombocytopenia (VITT) has emerged as a rare side-effect of vaccination against COVID-19. Cerebral venous thrombosis is the most common manifestation of this syndrome but, to our knowledge, has not previously been described in detail. We aimed to document the features of post-vaccination cerebral venous thrombosis with and without VITT and to assess whether VITT is associated with poorer outcomes.

METHODS

For this multicentre cohort study, clinicians were asked to submit all cases in which COVID-19 vaccination preceded the onset of cerebral venous thrombosis, regardless of the type of vaccine, interval between vaccine and onset of cerebral venous thrombosis symptoms, or blood test results. We collected clinical characteristics, laboratory results (including the results of tests for anti-platelet factor 4 antibodies where available), and radiological features at hospital admission of patients with cerebral venous thrombosis after vaccination against COVID-19, with no exclusion criteria. We defined cerebral venous thrombosis cases as VITT-associated if the lowest platelet count recorded during admission was below 150 × 10⁹ per L and, if the D-dimer was measured, the highest value recorded was greater than 2000 μg/L. We compared the VITT and non-VITT groups for the proportion of patients who had died or were dependent on others to help them with their activities of daily living (modified Rankin score 3-6) at the end of hospital admission (the primary outcome of the study). The VITT group were also compared with a large cohort of patients with cerebral venous thrombosis described in the International Study on Cerebral Vein and Dural Sinus Thrombosis.

FINDINGS

Between April 1 and May 20, 2021, we received data on 99 patients from collaborators in 43 hospitals across the UK. Four patients were excluded because they did not have definitive evidence of cerebral venous thrombosis on imaging. Of the remaining 95 patients, 70 had VITT and 25 did not. The median age of the VITT group (47 years, IQR 32-55) was lower than in the non-VITT group (57 years; 41-62; p=0·0045). Patients with VITT-associated cerebral venous thrombosis had more intracranial veins thrombosed (median three, IQR 2-4) than non-VITT patients (two, 2-3; p=0·041) and more frequently had extracranial thrombosis (31 [44%] of 70 patients) compared with non-VITT patients (one [4%] of 25 patients; p=0·0003). The primary outcome of death or dependency occurred more frequently in patients with VITT-associated cerebral venous thrombosis (33 [47%] of 70 patients) compared with the non-VITT control group (four [16%] of 25 patients; p=0·0061). This adverse outcome was less frequent in patients with VITT who received non-heparin anticoagulants (18 [36%] of 50 patients) compared with those who did not (15 [75%] of 20 patients; p=0·0031), and in those who received intravenous immunoglobulin (22 [40%] of 55 patients) compared with those who did not (11 [73%] of 15 patients; p=0·022).

INTERPRETATION

Cerebral venous thrombosis is more severe in the context of VITT. Non-heparin anticoagulants and immunoglobulin treatment might improve outcomes of VITT-associated cerebral venous thrombosis. Since existing criteria excluded some patients with otherwise typical VITT-associated cerebral venous thrombosis, we propose new diagnostic criteria that are more appropriate.

FUNDING

None.

Concern About the Adverse Effects of Thrombocytopenia and Thrombosis After Adenovirus-Vectored COVID-19 Vaccination

Since the outbreak of Covid-19 in December, 2019, scientists worldwide have been committed to developing COVID-19 vaccines. Only when most people have immunity to SARS-CoV-2, COVID-19 can reduce even wholly overcome. So far, nine kinds of COVID-19 vaccines have passed the phase III clinical trials and have approved for use. At the same time, adverse reactions after COVID-19 vaccination have also reported. This paper focuses on the adverse effects of thrombosis and thrombocytopenia caused by the COVID-19 vaccine, especially the adenovirus-vector vaccine from AstraZeneca and Pfizer, and discusses its mechanism and possible countermeasures.

Sex Differences in Adverse Reactions to an Inactivated SARS-CoV-2 Vaccine Among Medical Staff in China

Objective: We investigated whether there were sex differences in adverse reactions to an inactivated SARS-CoV-2 vaccine among medical staff in China. Methods: From 24 February to 7 March 2021 an online cross-sectional survey was conducted with a self-administered COVID-19 vaccine questionnaire among medical staff in Taizhou, China. In total, 1397 interviewees (1,107 women and 290 men) participated in the survey. Results: In our study, 178 (16.1%) women and 23 (7.9%) men reported adverse reactions following their first vaccination, and 169 (15.3%) women and 35 (12.1%) men reported adverse reactions following their second vaccination. After adjusting for confounding factors, adverse reactions to other vaccines, worry about adverse reactions, knowledge of the inactivated vaccine being used in the hospital, taking the vaccine for one's family proactively and receiving an influenza vaccination were significantly related to adverse reactions to both injections in women. In contrast, in men, concerns about adverse reactions independently increased the risk of adverse reactions following either vaccination, and a history of adverse reactions to other vaccines also increased the risk of adverse reactions to both injections. Conclusions: Sex differences in the frequency of reported adverse reactions to an inactivated SARS-CoV-2 vaccine and potential factors were demonstrated in a sample of medical staff.

Vaccine-induced immune thrombotic thrombocytopenia: current evidence, potential mechanisms, clinical implications, and future directions

Vaccine-induced immune thrombotic thrombocytopenia (VITT) (also termed thrombosis with thrombocytopenia syndrome or vaccine-induced thrombotic thrombocytopenia or vaccine-induced immune thrombocytopenia) is characterized by (i) venous or arterial thrombosis; (ii) mild-to-severe thrombocytopenia; (iii) positive antiplatelet factor 4 (PF4)-polyanion antibodies or anti-PF4-heparin antibodies detected by the HIT (heparin-induced thrombocytopenia) ELISA; (iv) occurring 5-30 days after ChAdOx1 nCoV-19 (AstraZeneca) or Ad26.COV2.S (Johnson & Johnson/Janssen) vaccination. VITT's incidence is 1 per 100 000 vaccinated people irrespective of age and up to 1 in 50 000 for people <50 years of age with the AstraZeneca COVID-19 vaccine. The exact mechanism by which adenovirus-vectored COVID-19 vaccines trigger this syndrome is still unclear, as for the increased risk for acute cerebral sinus venous thrombosis and splanchnic vein thrombosis as compared to other locations of venous thrombotic events. VITT is associated with the detection of anti-PF4 antibodies, unrelated to previous use of heparin therapy. PF4 antibodies are thought to activate platelets via the platelet FcγRIIA receptors leading to further platelet activation that causes thrombosis and thrombocytopenia.

Thrombotic events and COVID-19 vaccines

COVID-19 vaccines are considered promising agents in the control of the pandemic. Although their safety was assessed in randomised clinical trials, severe adverse events (AEs) have been reported after large-scale administration. This study aims to evaluate thromboembolic AEs reported after vaccination in a real-world context and how they led to the interruption of vaccination campaigns. We also review the benefits and risks of the vaccines approved in the European Union and provide recommendations. A review of the literature was performed using Medline/PubMed electronic database as well as institutional and pharmacovigilance official reports. Our findings show that vaccine-induced prothrombotic immune thrombocytopenia has been suggested as a very rare AE associated with viral vector vaccines. Unusual thrombotic events combined with moderate-to-severe thrombocytopenia were reported mainly in women under 60 years of age. As safety signals emerged, Vaxzevria and Janssen´s COVID-19 vaccine campaigns have been paused while investigations proceed. On the other hand, the number of deep vein thrombosis and pulmonary embolism reports have not increased. Post-marketing surveillance indicated that mRNA vaccines are safe and should continue to be used. The thrombotic events report rate is not increased in people over 60 years. As they are at greater risk for COVID-19 complications and death, no vaccine restrictions are recommended in this group. Risk factors for vaccine-induced prothrombotic immune thrombocytopenia should be established so that evidence-based decisions can be made. Systematic monitoring of COVID-19 vaccine safety is essential to ensure that the benefits of vaccination outweigh the risks.

Comparing Results of Five SARS-CoV-2 Antibody Assays Before and After the First Dose of ChAdOx1 nCoV-19 Vaccine among Health Care Workers

Reliable results regarding serologic positivity for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody before and after AstraZeneca (AZ) vaccination are essential for estimating the efficacy of vaccination. We assessed positivity rates and associated factors using five SARS-CoV-2 antibody assays. A total of 228 paired serum samples (456 samples) were obtained from 228 participants. After baseline sampling, the second sampling was conducted between 11 and 28 days after the first dose of the AZ vaccine. Sera were tested using five SARS-CoV-2 antibody assays, including two surrogate virus neutralization tests. A questionnaire on the symptoms, severity, and duration of adverse reactions was completed by all participants. The overall positivity rates for SARS-CoV-2 antibody were 84.6% for the Roche assay, 92.5% for the Abbott assay, 75.4% for the Siemens assay, 90.7% for the SD Biosensor assay, and 66.2% for the GenScript assay after the first dose of the AZ vaccine. The positivity rates and antibody titers of sera obtained between 21 and 28 days were significantly higher than those obtained between 11 and 20 days in all five assays. More-severe adverse reactions and longer durations of adverse reactions were related to higher SARS-CoV-2 antibody levels. The agreements and correlations among the assays applied were substantial (к, 0.73 to 0.95) and strong (ρ, 0.83 to 0.91). A single dose of the AZ vaccine led to high positivity rates based on the five assays. Days after vaccination and adverse reactions could help estimate serologic conversion rates. The results should be interpreted cautiously considering the assays and cutoffs applied. Our findings could inform decisions regarding vaccination and laboratory settings and could thus contribute to the control of the spread of SARS-CoV-2 infection.

Extensive thrombosis after COVID-19 vaccine: cause or coincidence?

A 62-year-old Caucasian female patient presented with abdominal pain, vomiting and fever 1 day after administration of COVID-19 vaccine. Bloodwork revealed anaemia and thrombocytosis. Abdominal CT angiography showed a mural thrombus at the emergence of the coeliac trunk, hepatic and splenic arteries, and extensive thrombosis of the superior and inferior mesenteric veins, splenic and portal veins, and the inferior vena cava, extending to the left common iliac vein. The spleen displayed extensive areas of infarction. Aetiological investigation included assessment of congenital coagulation disorders and acquired causes with no relevant findings. Administration of COVID-19 vaccine was considered a possible cause of the extensive multifocal thrombosis. After reviewing relevant literature, it was considered that other causes of this event should be further investigated. Thrombosis associated with COVID-19 vaccine is rare and an aetiological relationship should only be considered in the appropriate context and after investigation of other, more frequent, causes.

A Case of Acute Pulmonary Embolus after mRNA SARS-CoV-2 Immunization

Vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), is a critical strategy to overcome the COVID-19 pandemic. Multiple SARS-CoV-2 vaccines have been developed in a rapid timeframe to combat the pandemic. While generally safe and effective, rare cases of venous thromboembolism (VTE) have been reported after two adenovirus-based vaccines, the AstraZeneca ChAdOx1 nCoV-19 vaccine and the Janssen Ad.26.COV2.S vaccine, as well as after the Pfizer-BioNTech BNT162b2 mRNA vaccine. Here, we present the case of a patient who developed acute pulmonary emboli (PE) shortly after his second dose of the Moderna mRNA-1273 SARS-CoV-2 vaccine. We report the results of an extensive thrombophilia workup that was normal except for the identification of positive lupus anticoagulant (LA) signals. It is our goal to contribute to the body of knowledge regarding SARS-CoV-2 vaccines and encourage vaccine adverse event reporting so that clinicians can have a full appreciation and awareness of the possible adverse events related to these critical vaccines.

Deterioration of vaccine-induced immune thrombotic thrombocytopenia treated by heparin and platelet transfusion: Insight from functional cytometry and serotonin release assay

We report a case of a 62-year-old man who developed cerebral venous sinus thrombosis with subarachnoid hemorrhage and concomitant thrombocytopenia, which occurred 13 days after ChAdOx1 nCov-19 injection. The patient died in the intensive care unit after heparin infusion and platelet transfusion. The key clinical purpose of this case report is to better understand how to confirm vaccine-induced immune thrombotic thrombocytopenia (VITT). VITT diagnosis was made using 14C-serotonin release and flow cytometry evaluating activation and platelet microvesicles on washed platelets. Four control patients were examined: a patient with heparin-induced thrombocytopenia (HIT), two patients with thrombotic events without thrombocytopenia after ChAdOx1 nCov-19 or BNT162b2, and a patient with suspected HIT and an excluded diagnosis. We evidenced in the VITT case a high level of IgG anti-platelet factor 4-heparin antibodies associated with a high level of platelet activation in the absence of heparin. Conversely, the functional assays were negative in the patients with thrombosis without thrombocytopenia.

Adverse rare events to vaccines for COVID-19: From hypersensitivity reactions to thrombosis and thrombocytopenia

Vaccines for the prevention of coronavirus disease 2019 (COVID-19) started to be developed since the initiation of the COVID-19 pandemic. Up to now, four vaccines have been authorized by international agencies such as European Medicines Agency (EMA). Two are DNA vaccines (ChAdOx1 nCov-19 and Ad26.COV2.S) and two mRNA vaccines (BNT162b2 and mRNA-1273). The administration of the vaccines has been associated with a strong decrease in the infections by SARS-CoV-2 and deaths associated with it. However, in parallel to these results, some rare adverse events have also been described. In that sense, events of thrombosis, thrombocytopenia, and hemorrhage have been described in close temporal proximity to the administration of the DNA vaccines ChAdOx1 nCov-19 and Ad26.COV2.S, but also mRNA vaccines. Recent scientific reports have been released with updated information on the possible association of thrombotic thrombocytopenia and COVID-19 vaccines. On the other hand, since the initiation of the vaccination campaigns, adverse hypersensitivity reactions have been described after mRNA and DNA vaccines administration for COVID-19. Although globally these adverse events are rare, a high proportion of the world population will be exposed to these vaccines. For that reason, their safety and tolerance should be carefully considered. In this review, we provide an updated review of the last scientific findings that can explain the rare side effects that the vaccines for COVID-19 can produce.

Thrombotic complications of vaccination against SARS-CoV-2: what pharmacovigilance reports tell us - and what they don't

In the present issue of the European Respiratory Journal, Smadjaet al. [1] present an analysis of global pharmacovigilance reports of thrombotic events following severe acute respiratory distress syndrome coronavirus 2 (SARS-CoV-2) vaccination. More specifically, the authors analysed the data entered into the World Health Organization (WHO) Global Database for Individual Case Safety Reports (VigiBase) between 13 December, 2020 and 16 March, 2021, covering, at that time, a population of almost 362 million vaccinated individuals across the world. The study focuses on three of the coronavirus disease 2019 (COVID-19) vaccines available to date, namely Pfizer-BioNtech (BNT162b2), Moderna (mRNA-1273) and OxfordAstraZeneca (ChAdOx1 nCov-19). The study by Smadjaet al. [1] confirms the rarity of possible thrombotic complications in association with COVID-19 vaccination, reporting only 0.21 (95% CI 0.19–0.22) cases of thrombotic events per million person vaccinated-days. However, there were also some unexpected observations which deserve closer attention and cautious interpretation.

Thrombotic complications of COVID-19 vaccination are very rare, but awareness is needed https://bit.ly/3n4vaXe

COVID-19 is a systemic vascular hemopathy: insight for mechanistic and clinical aspects

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is presenting as a systemic disease associated with vascular inflammation and endothelial injury. Severe forms of SARS-CoV-2 infection induce acute respiratory distress syndrome (ARDS) and there is still an ongoing debate on whether COVID-19 ARDS and its perfusion defect differs from ARDS induced by other causes. Beside pro-inflammatory cytokines (such as interleukin-1 β [IL-1β] or IL-6), several main pathological phenomena have been seen because of endothelial cell (EC) dysfunction: hypercoagulation reflected by fibrin degradation products called D-dimers, micro- and macrothrombosis and pathological angiogenesis. Direct endothelial infection by SARS-CoV-2 is not likely to occur and ACE-2 expression by EC is a matter of debate. Indeed, endothelial damage reported in severely ill patients with COVID-19 could be more likely secondary to infection of neighboring cells and/or a consequence of inflammation. Endotheliopathy could give rise to hypercoagulation by alteration in the levels of different factors such as von Willebrand factor. Other than thrombotic events, pathological angiogenesis is among the recent findings. Overexpression of different proangiogenic factors such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-2) or placental growth factors (PlGF) have been found in plasma or lung biopsies of COVID-19 patients. Finally, SARS-CoV-2 infection induces an emergency myelopoiesis associated to deregulated immunity and mobilization of endothelial progenitor cells, leading to features of acquired hematological malignancies or cardiovascular disease, which are discussed in this review. Altogether, this review will try to elucidate the pathophysiology of thrombotic complications, pathological angiogenesis and EC dysfunction, allowing better insight in new targets and antithrombotic protocols to better address vascular system dysfunction. Since treating SARS-CoV-2 infection and its potential long-term effects involves targeting the vascular compartment and/or mobilization of immature immune cells, we propose to define COVID-19 and its complications as a systemic vascular acquired hemopathy.

Thrombotic Thrombocytopenia after COVID-19 Vaccination: In Search of the Underlying Mechanism

The rollout of COVID-19 vaccines brings hope for successful pandemic mitigation and getting the transmission of SARS-CoV-2 under control. The vaccines authorized in Europe displayed a good safety profile in the clinical trials. However, during their post-authorization use, unusual thrombotic events associated with thrombocytopenia have rarely been reported for vector vaccines. This led to the temporary suspension of the AZD1222 vaccine (Oxford/AstraZeneca) in various European countries and the Ad26.COV2 vaccine (Janssen/Johnson&Johnson) in the United States, with regulatory bodies launching investigations into potential causal associations. The thromboembolic reactions were also rarely reported after mRNA vaccines. The exact cause of these adverse effects remains to be elucidated. The present paper outlines the hypotheses on the mechanisms behind the very rare thrombotic thrombocytopenia reported after the COVID-19 vaccination, along with currently existing evidence and future research prospects. The following are discussed: (i) the role of antibodies against platelet factor 4 (PF4), (ii) the direct interaction between adenoviral vector and platelets, (iii) the cross-reactivity of antibodies against SARS-CoV-2 spike protein with PF4, (iv) cross-reactivity of anti-adenovirus antibodies and PF4, (v) interaction between spike protein and platelets, (vi) the platelet expression of spike protein and subsequent immune response, and (vii) the platelet expression of other adenoviral proteins and subsequent reactions. It is also plausible that thrombotic thrombocytopenia after the COVID-19 vaccine is multifactorial. The elucidation of the causes of these adverse events is pivotal in taking precautionary measures and managing vaccine hesitancy. It needs to be stressed, however, that the reported cases are currently sporadic and that the benefits of COVID-19 vaccines vastly outweigh their potential risks.