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Coronavirus disease-19 (COVID-19) vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare but serious clinical condition with high mortality rate in apparently healthy individuals without noticeable risk factors. VITT typically arises due to the administration of vaccines that possess recombinant adenoviral vectors, including ChAdOx1 nCov-19 (AstraZeneca) and Ad26 COV2.S (Johnson & Johnson/Janssen). Thrombosis frequently occurs at atypical sites, such as the cerebral or splanchnic circulations, in this particular pathological state. Similar to heparin-induced thrombotic thrombocytopenia (HITT), it seems that the cause of VITT is the misdirection of anti-platelet factor 4 antibodies (anti-PF4 Abs), an ancient antimicrobial mechanism. Anti-PF4 Abs in patients with VITT activates the coagulation system, leading to thrombosis. This process occurs through the stimulation of platelets (Plts) and neutrophils and subsequently release of neutrophil extracellular traps (NETs). Due to the potentially fatal consequences of VITT, early diagnosis is mandatory. In addition to thrombocytopenia, thrombosis, and the presence of anti-PF4 Abs, the day of symptoms onset and the elevation of D-dimer are also required for definitive diagnosis of VITT. The absence of one or more criteria can result in the exclusion of definitive VITT and lead to the diagnosis of probable, possible, or unlikely VITT., Competing Interests: Declarations. Ethical approval: This article does not contain any studies with human participants or animals performed by any of the authors. Conflict of Interest: The authors declare no competing interests., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare adverse event identified following vaccination with some adenovirus-vectored COVID-19 vaccines, including Ad26.COV2.S. VITT is characterized by the presence of antibodies against platelet factor 4 (PF4)., Objectives: To evaluate whether PF4 antibodies were generally induced following vaccination with adenovirus type 26 (Ad26)-vectored vaccines., Methods: The study included 913 and 991 healthy participants without thromboembolic (TE) events in Ad26.COV2.S and non-COVID-19 Ad26-vectored vaccine clinical studies, respectively, and 1 participant with VITT following Ad26.COV2.S vaccination. PF4 antibody levels were measured in prevaccination and postvaccination sera. PF4 antibody positivity rates were assessed in a case-control setting in participants who developed TE events during participation in Ad26-vectored vaccine clinical studies., Results: In the 1 VITT patient, PF4 antibodies were negative before vaccination. Seroconversion for platelet-activating PF4 antibodies was observed upon Ad26.COV2.S vaccination. In participants without TE events, the PF4 antibody levels and positivity rates were similar before and after Ad26 vaccination. Ad26 vaccination did not increase PF4 antibody levels in participants who were PF4 antibody-positive at baseline (n = 47). Lastly, 1 out of 28 TE cases and 2 out of 156 non-TE controls seroconverted after Ad26.COV2.S vaccination. None of the 15 TE cases and 3 of the 77 non-TE controls seroconverted following non-COVID-19 Ad26 vaccination., Conclusion: Ad26.COV2.S and the other Ad26-vectored vaccines studied did not generally induce PF4 antibodies or increase preexisting PF4 antibody levels. Moreover, unlike VITT, TE events that occurred at any time following Ad26 vaccination were not associated with PF4 antibodies., Competing Interests: Declaration of competing interests All authors were full-time employees of Johnson & Johnson at the time of the study and may have equity or stocks in Johnson & Johnson. F.S. is a former employee of GlaxoSmithKline and holds GlaxoSmithKline equity or stocks., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

2.5 × 1010 vp Ad26.COV2.S elicited robust SARS-CoV-2-specific antibody responses in adolescents through 6 months, with acceptable safety and reactogenicity profiles. Compared with adults immunized with 5 × 1010 vp Ad26.COV2.S, adolescents had higher antibody levels, despite being vaccinated with a lower dose., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Journal of the Pediatric Infectious Diseases Society.)

Vaccine-induced immune thrombocytopenia and thrombosis (VITT) is a newly recognized syndrome mediated by anti-platelet factor 4 antibodies induced by Covid-19 adenovirus-vectored vaccines including ChAdOx1 nCoV-19 and Ad26.COV2.S. This study validated a proposed Brighton Collaboration case definition for VITT. A data collection form was developed and used to capture the variations in VITT criteria and assess their level of diagnostic certainty from adjudicated positive VITT case datasheets in Germany (n = 71), UK (n = 220), Australia (n = 203), and Taiwan (n = 56). We observed high prevalence of each component of the proposed VITT definition in positive cases (84%-100%), except for the occurrence of thrombosis or thromboembolism criterion in only 34% of VITT cases in Taiwan. The sensitivity of this proposed definition was 100% for Germany and UK, 92% for Australia, and 89% for Taiwan cases. These findings support the validity of this case definition for VITT., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: H. Tran reports project grant funding support outside of the submitted work from AstraZeneca and Sanofi. W.-I. Huang is a member of the national enhanced passive Covid-19 vaccine safety surveillance team in Taiwan. J. Buttery has served as an independent data monitoring committee member for CEPI SPEAC, GSK, Serum Institute of India, SK Biosciences and Clover Vaccines. His employer Murdoch Children’s Research Institute is compensated for his time. A. Greinacher reports grants and non-financial support from Aspen, Boehringer Ingelheim, MSD, Bristol Myers Squibb (BMS), Paringenix, Bayer Healthcare, Gore Inc., Rovi, Sagent, Biomarin/Prosensa, personal fees from Aspen, Boehringer Ingelheim, MSD, Macopharma, BMS, Chromatec, Werfen, nonfinancial support from Boehringer Ingelheim, Portola, Ergomed, GTH e.V. outside the submitted work. No other authors report conflicts of interest. Parts of the German results reported have been obtained in a study conducted by Universitätsmedizin Greifswald under service contract No. EMA/2021/17/TDA. The views expressed are the personal views of the authors and may not be understood or quoted as being made on behalf of or reflecting the position of the European Medicines Agency or one of its Committees or Working Parties. The Taiwan VITT case information was based on data provided by the Vaccine Adverse Event Reporting System, operated by Taiwan Centers for Disease Control., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background and Objective: Cases of appendicitis were identified in the pivotal randomized clinical trial on BNT162b2 mRNA vaccine and reported from coronavirus disease 2019 (COVID-19) vaccine pharmacovigilance systems. Three cohort studies and two self-controlled case series (SCCS) studies evaluating the association between mRNA vaccines and appendicitis reported discordant results. To address this uncertainty, the present study examines in a large population, with a SCCS design, the association between mRNA (BNT162b2 and mRNA-1273) and, for the first time, viral vector (ChAdOx1-S and Ad26.COV2-S) COVID-19 vaccines and acute appendicitis., Methods: The SCCS study design was used to evaluate the association between COVID-19 vaccination and subsequent onset of acute appendicitis. The study was based on record linkage of health archives through TheShinISS application, a statistical tool that locally processes data from regional health care databases according to ad hoc, study-tailored and common data model. The study population included all vaccinated subjects ≥ 12 years old between 27 December 2020 and 30 September 2021. The acute appendicitis was identified through discharge diagnoses of hospital admissions or emergency department visits. Incident cases were defined as those who experienced a first event of acute appendicitis in the study period, excluding subjects with a diagnosis of appendicitis in the previous 5 years. Exposure was defined as the first or second dose of BNT162b2, mRNA-1273 and ChAdOx1-S and the single dose of Ad26.COV2-S. The risk interval was defined as 42 days from the first or second vaccination dose and divided into pre-specified risk subperiods; the reference period was the observation time outside the risk interval. Relative incidences (RI) and 95% confidence intervals (95% CI) were estimated with the SCCS method 'modified for event-dependent exposures', through unbiased estimating equations. The seasonal component was considered as a time-dependent covariate., Results: In the 42-day risk interval 1285 incident cases of acute appendicitis occurred: 727 cases after the first dose and 558 cases after the second dose. In the main analysis, no increased risks of acute appendicitis were observed in subjects vaccinated with BNT162b, mRNA-1273, ChAdOx1-S and Ad26.COV2-S. The subgroup analyses by sex showed an increased risk in the 14-27 day risk interval, in males after the first dose of mRNA-1273 (RI of 1.71; 95% CI 1.08-2.70, p = 0.02) and in females after the single dose of Ad26.COV2-S (RI of 4.40; 95% CI 1.29-15.01, p = 0.02)., Conclusions: There was no evidence of association of BNT162b, ChAdOx1-S, mRNA-1273 and Ad26.COV2-S with acute appendicitis in the general population. The results of the subgroup analyses by sex needs to be considered with caution. The multiplicity issue cannot be excluded being these hypotheses two of several hypotheses tested. In addition, relevant literature on the biological mechanism of the disease and evidence of similar effects with other vaccines or with the same vaccines are still lacking to provide strong support for a conclusion that there is an harmful effect in males and females with mRNA-1273 and Ad26.COV2-S., (© 2024. The Author(s).)

Objective: To review cases of optic neuritis after COVID-19 vaccination and add similar cases to the literature., Methods: Thorough PubMed and Scopus searches were conducted, and data from studies describing optic neuritis after COVID-19 vaccination were extracted, tabulated, pooled, and reviewed., Results: We present 6 cases of optic neuritis following COVID-19 vaccination. Our literature search yielded 48 similar cases. All 54 cases were divided into 3 groups with respect to their serostatus: (1) double-seronegative or unknown serostatus optic neuritis cases, (2) myelin oligodendrocyte glycoprotein (MOG)-associated optic neuritis cases, and (3) aquaporin-4-associated optic neuritis cases. Data from each group were separately pooled and reviewed. While the most frequent vaccine among the anti-AQP4+ subgroup was BNT162b2 (Pfizer-BioNTech) (2/3), recombinant vaccines, e.g., AZD122 and Ad26.Cov2.s were mostly injected in the other subgroups (23/51). No significant gender inclination was seen among different subgroups. The mean interval from vaccination to symptom onset was less than one month in all subgroups; symptom manifestations mainly occurred after the first dose (28/54). Almost all cases showed improvement after steroid therapy±plasma exchange (52/54)., Conclusion: Despite having rare side effects such as optic neuritis, vaccination remains our most helpful protection against SARS-CoV-2. Nevertheless, larger studies are needed to ascertain the pathophysiology of such adverse effects. Likewise, the association between COVID-19 vaccination and optic neuritis warrants further investigation., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Importance: Understanding the potential risk of uveitis recurrence after COVID-19 vaccination in individuals with a history of uveitis is crucial for vaccination strategies and clinical monitoring., Objective: To investigate the risk of uveitis recurrence after COVID-19 vaccination in a cohort of individuals with a history of uveitis., Design, Setting, and Participants: This retrospective population-based cohort study included individuals diagnosed with uveitis between January 1, 2015, and February 25, 2021, in South Korea. After excluding individuals without COVID-19 vaccination or with SARS-CoV-2 infection, individuals with a history of uveitis who had received at least 1 dose of a messenger RNA (BNT162b2 [Pfizer-BioNTech] or mRNA-1273 [Moderna]) or adenovirus vector-based (ChAdOx1 [AstraZeneca] or Ad26.COV2.S [Janssen]) COVID-19 vaccine were included. Data were analyzed from February 26, 2021, to December 31, 2022., Exposure: Demographic and clinical data, along with vaccination details, were retrieved from the Korean National Health Insurance Service and Korea Disease Control and Prevention Agency databases., Main Outcomes and Measures: Outcomes of interest were incidence and risk of postvaccination uveitis in association with different COVID-19 vaccines and periods before and after COVID-19 vaccination. Uveitis was categorized by onset (early, within 30 days, or delayed) and type (anterior or nonanterior). Hazard ratios (HRs) with 95% CIs were calculated to evaluate the risk of uveitis following COVID-19 vaccination, stratified according to vaccine type and vaccination period., Results: Of 543 737 individuals with history of uveitis, 473 934 individuals (mean [SD] age, 58.9 [17.4] years; 243 127 [51.3] female) had documented COVID-19 vaccination and were included in analysis. The cumulative incidence of postvaccination uveitis was 8.6% at 3 months, 12.5% at 6 months, and 16.8% at 1 year, predominantly of the anterior type. Variations in the risk of postvaccination uveitis were observed across different vaccines and intervaccination periods. The risk of early postvaccination uveitis was increased for individuals receiving the BNT162b2 (HR, 1.68; 95% CI, 1.52-1.86), mRNA-1273 (HR, 1.51; 95% CI, 1.21-1.89), ChAdOx1 (HR, 1.60; 95% CI, 1.43-1.79), and Ad26.COV2.S (HR, 2.07; 95% CI, 1.40-3.07) vaccines. The risk of uveitis was higher particularly between the first and second vaccination doses (HR, 1.64; 95% CI, 1.55-1.73)., Conclusions and Relevance: These findings suggest that there was an elevated risk of uveitis following COVID-19 vaccination, with the vaccine type and period mediating this risk. For individuals with a history of uveitis, clinicians should consider the potential risk of uveitis recurrence in vaccination strategies and clinical monitoring.

Cases that experienced COVID-19 postvaccination-related thrombosis have been reported after the first dose of ChAdOx1 nCov-19 (Vaxzevria, AstraZeneca) or Ad26.COV2.S (Johnson & Johnson/Janssen) vaccine. These rare thrombotic events were observed within the expected vaccine-induced seroconversion period and could be attributed to platelet-activating (auto)antibodies against platelet factor 4 (PF4). Newly, vaccine-induced, cross-reactive anti-PF4 antibodies could explain this observation. An in-silico analysis using the Basic Local Alignment Search Tool was used to identify sequence similarity between PF4 and antigens contained in or encoded by ChAdOx1 nCov-19 or Ad26.COV2.S vaccines. Only one sequence within the signaling peptide of the SARS-CoV-2 spike protein exhibited a high percent identity (85.71%) with PF4. This sequence overlaps with a proven immunogenic peptide recognized from convalescent COVID-19 sera and could be responsible for the formation of platelet-activating immunocomplexes in susceptible patients. Manipulation of the immunogenicity of this particular sequence within the encoded SARS-CoV-2 spike protein signaling peptide may eliminate this iatrogenic severe adverse effect.

Objective: To quantify the comparative risk of thrombosis with thrombocytopenia syndrome or thromboembolic events associated with use of adenovirus based covid-19 vaccines versus mRNA based covid-19 vaccines., Design: International network cohort study., Setting: Routinely collected health data from contributing datasets in France, Germany, the Netherlands, Spain, the UK, and the US., Participants: Adults (age ≥18 years) registered at any contributing database and who received at least one dose of a covid-19 vaccine (ChAdOx1-S (Oxford-AstraZeneca), BNT162b2 (Pfizer-BioNTech), mRNA-1273 (Moderna), or Ad26.COV2.S (Janssen/Johnson & Johnson)), from December 2020 to mid-2021., Main Outcome Measures: Thrombosis with thrombocytopenia syndrome or venous or arterial thromboembolic events within the 28 days after covid-19 vaccination. Incidence rate ratios were estimated after propensity scores matching and were calibrated using negative control outcomes. Estimates specific to the database were pooled by use of random effects meta-analyses., Results: Overall, 1 332 719 of 3 829 822 first dose ChAdOx1-S recipients were matched to 2 124 339 of 2 149 679 BNT162b2 recipients from Germany and the UK. Additionally, 762 517 of 772 678 people receiving Ad26.COV2.S were matched to 2 851 976 of 7 606 693 receiving BNT162b2 in Germany, Spain, and the US. All 628 164 Ad26.COV2.S recipients from the US were matched to 2 230 157 of 3 923 371 mRNA-1273 recipients. A total of 862 thrombocytopenia events were observed in the matched first dose ChAdOx1-S recipients from Germany and the UK, and 520 events after a first dose of BNT162b2. Comparing ChAdOx1-S with a first dose of BNT162b2 revealed an increased risk of thrombocytopenia (pooled calibrated incidence rate ratio 1.33 (95% confidence interval 1.18 to 1.50) and calibrated incidence rate difference of 1.18 (0.57 to 1.8) per 1000 person years). Additionally, a pooled calibrated incidence rate ratio of 2.26 (0.93 to 5.52) for venous thrombosis with thrombocytopenia syndrome was seen with Ad26.COV2.S compared with BNT162b2., Conclusions: In this multinational study, a pooled 30% increased risk of thrombocytopenia after a first dose of the ChAdOx1-S vaccine was observed, as was a trend towards an increased risk of venous thrombosis with thrombocytopenia syndrome after Ad26.COV2.S compared with BNT162b2. Although rare, the observed risks after adenovirus based vaccines should be considered when planning further immunisation campaigns and future vaccine development., Competing Interests: Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/disclosure-of-interest/ and declare: support from the EMA for the submitted work; DP-A receives funding from the UK National Institute for Health Research (NIHR) in the form of a senior research fellowship and from the Oxford NIHR Biomedical Research Centre. XL receives the Clarendon Fund and Brasenose College scholarship (University of Oxford) to support her DPhil study. DP-A’s research group has received research grants from the EMA; Innovative Medicines Initiative; and Amgen, Chiesi, and UCB Biopharma; and consultancy or speaker fees from Astellas, Amgen, AstraZeneca, and UCB Biopharma. LHJ works for a research group who receives unconditional research grants from Yamanouchi, Pfizer-Boehringer Ingelheim, Novartis, GSK, Chiesi, Astra-Zeneca, Amgen, Janssen Research and Development. PR works for a research group who receives unconditional research grants from Yamanouchi, Pfizer-Boehringer Ingelheim, Novartis, GSK, Chiesi, Astra-Zeneca, Amgen, Janssen Research and Development. CC has no conflicts of interest. None of these declarations relate to the content of this paper., (© Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: People living with HIV (PLWH) have been reported to have a higher risk of more severe COVID-19 disease and death. We assessed the ability of the Ad26.CoV2.S vaccine to elicit neutralizing activity against the Delta variant in PLWH relative to HIV-negative individuals. We also examined effects of HIV status and suppression on Delta neutralization response in SARS-CoV-2-infected unvaccinated participants., Methods: We enrolled participants who were vaccinated through the SISONKE South African clinical trial of the Ad26.CoV2.S vaccine in healthcare workers (HCWs). PLWH in this group had well-controlled HIV infection. We also enrolled unvaccinated participants previously infected with SARS-CoV-2. Neutralization capacity was assessed by a live virus neutralization assay of the Delta variant., Results: Most Ad26.CoV2.S vaccinated HCWs were previously infected with SARS-CoV-2. In this group, Delta variant neutralization was 9-fold higher compared with the infected-only group and 26-fold higher relative to the vaccinated-only group. No decrease in Delta variant neutralization was observed in PLWH relative to HIV-negative participants. In contrast, SARS-CoV-2-infected, unvaccinated PLWH showed 7-fold lower neutralization and a higher frequency of nonresponders, with the highest frequency of nonresponders in people with HIV viremia. Vaccinated-only participants showed low neutralization capacity., Conclusions: The neutralization response of the Delta variant following Ad26.CoV2.S vaccination in PLWH with well-controlled HIV was not inferior to HIV-negative participants, irrespective of past SARS-CoV-2 infection. In SARS-CoV-2-infected and nonvaccinated participants, HIV infection reduced the neutralization response to SARS-CoV-2, with the strongest reduction in HIV viremic individuals., (© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.)

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

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a life-threatening syndrome of aggressive thrombosis, often profound thrombocytopenia, and frequently overt disseminated intravascular coagulation. It has been associated with 2 adenovirus vector COVID-19 vaccines: ChAdOx1 nCoV-19 (AstraZeneca) and Ad26.COV2.S (Janssen). Unlike the myriad of other conditions that cause thrombosis and thrombocytopenia, VITT has an important distinguishing feature: affected individuals have platelet activating anti-PF4 antibodies that appear in a predictable time frame following vaccination. The reported incidence of VITT differs between jurisdictions; it is dependent on accurate ascertainment of cases and accurate estimates of the size of the vaccinated population. The incidence ranges from 1 case per 26,500 to 127,3000 first doses of ChAdOx1 nCoV-19 administered. It is estimated at 1 case per 518,181 second doses of ChAdOx1 nCoV-19 administered, and 1 case per 263,000 Ad26.COV2.S doses administered. There are no clear risk factors for VITT, including sex, age, or comorbidities. VITT is a rare event, but its considerable morbidity and mortality merit ongoing pharmacovigilance, and accurate case ascertainment., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: Thrombosis with thrombocytopenia syndrome (TTS) is a potentially life-threatening condition associated with adenoviral-vectored COVID-19 vaccination. It presents similarly to spontaneous heparin-induced thrombocytopenia. Twelve cases of cerebral venous sinus thrombosis after vaccination with the Ad26.COV2.S COVID-19 vaccine (Janssen/Johnson & Johnson) have previously been described., Objective: To describe surveillance data and reporting rates of all reported TTS cases after COVID-19 vaccination in the United States., Design: Case series., Setting: United States., Patients: Case patients receiving a COVID-19 vaccine from 14 December 2020 through 31 August 2021 with thrombocytopenia and thrombosis (excluding isolated ischemic stroke or myocardial infarction) reported to the Vaccine Adverse Event Reporting System. If thrombosis was only in an extremity vein or pulmonary embolism, a positive enzyme-linked immunosorbent assay for antiplatelet factor 4 antibodies or functional heparin-induced thrombocytopenia platelet test result was required., Measurements: Reporting rates (cases per million vaccine doses) and descriptive epidemiology., Results: A total of 57 TTS cases were confirmed after vaccination with Ad26.COV2.S ( n  = 54) or a messenger RNA (mRNA)-based COVID-19 vaccine ( n  = 3). Reporting rates for TTS were 3.83 per million vaccine doses (Ad26.COV2.S) and 0.00855 per million vaccine doses (mRNA-based COVID-19 vaccines). The median age of patients with TTS after Ad26.COV2.S vaccination was 44.5 years (range, 18 to 70 years), and 69% of patients were women. Of the TTS cases after mRNA-based COVID-19 vaccination, 2 occurred in men older than 50 years and 1 in a woman aged 50 to 59 years. All cases after Ad26.COV2.S vaccination involved hospitalization, including 36 (67%) with intensive care unit admission. Outcomes of hospitalizations after Ad26.COV2.S vaccination included death (15%), discharge to postacute care (17%), and discharge home (68%)., Limitations: Underreporting and incomplete case follow-up., Conclusion: Thrombosis with thrombocytopenia syndrome is a rare but serious adverse event associated with Ad26.COV2.S vaccination. The different demographic characteristics of the 3 cases reported after mRNA-based COVID-19 vaccines and the much lower reporting rate suggest that these cases represent a background rate., Primary Funding Source: Centers for Disease Control and Prevention.

In hundreds of patients worldwide, vaccination against COVID-19 with adenovirus vector vaccines (ChAdOx1 nCoV-19; Ad26.COV2.S) triggered platelet-activating anti-platelet factor 4 (PF4) antibodies inducing vaccine-induced immune thrombotic thrombocytopenia (VITT). In most VITT patients, platelet-activating anti-PF4-antibodies are transient and the disorder is discrete and non-recurring. However, in some patients platelet-activating antibodies persist, associated with recurrent thrombocytopenia and sometimes with relapse of thrombosis despite therapeutic-dose anticoagulation. Anti-PF4 IgG antibodies measured by enzyme-immunoassay (EIA) are usually detectable for longer than platelet-activating antibodies in functional assays, but duration of detectability is highly assay-dependent. As more than 1 vaccination dose against COVID-19 is required to achieve sufficient protection, at least 69 VITT patients have undergone subsequent vaccination with an mRNA vaccine, with no relevant subsequent increase in anti-PF4 antibody titers, thrombocytopenia, or thrombotic complications. Also, re-exposure to adenoviral vector-based vaccines in 5 VITT patients was not associated with adverse reactions. Although data are limited, vaccination against influenza also appears to be safe. SARS-CoV-2 infection reported in 1 patient with preceding VITT did not influence anti-PF4 antibody levels. We discuss how these temporal characteristics of VITT provide insights into pathogenesis., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: The Ad26.COV2.S vaccine was highly effective against severe-critical coronavirus disease 2019 (Covid-19), hospitalization, and death in the primary phase 3 efficacy analysis., Methods: We conducted the final analysis in the double-blind phase of our multinational, randomized, placebo-controlled trial, in which adults were assigned in a 1:1 ratio to receive single-dose Ad26.COV2.S (5×10 10 viral particles) or placebo. The primary end points were vaccine efficacy against moderate to severe-critical Covid-19 with onset at least 14 days after administration and at least 28 days after administration in the per-protocol population. Safety and key secondary and exploratory end points were also assessed., Results: Median follow-up in this analysis was 4 months; 8940 participants had at least 6 months of follow-up. In the per-protocol population (39,185 participants), vaccine efficacy against moderate to severe-critical Covid-19 at least 14 days after administration was 56.3% (95% confidence interval [CI], 51.3 to 60.8; 484 cases in the vaccine group vs. 1067 in the placebo group); at least 28 days after administration, vaccine efficacy was 52.9% (95% CI, 47.1 to 58.1; 433 cases in the vaccine group vs. 883 in the placebo group). Efficacy in the United States, primarily against the reference strain (B.1.D614G) and the B.1.1.7 (alpha) variant, was 69.7% (95% CI, 60.7 to 76.9); efficacy was reduced elsewhere against the P.1 (gamma), C.37 (lambda), and B.1.621 (mu) variants. Efficacy was 74.6% (95% CI, 64.7 to 82.1) against severe-critical Covid-19 (with only 4 severe-critical cases caused by the B.1.617.2 [delta] variant), 75.6% (95% CI, 54.3 to 88.0) against Covid-19 leading to medical intervention (including hospitalization), and 82.8% (95% CI, 40.5 to 96.8) against Covid-19-related death, with protection lasting 6 months or longer. Efficacy against any severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection was 41.7% (95% CI, 36.3 to 46.7). Ad26.COV2.S was associated with mainly mild-to-moderate adverse events, and no new safety concerns were identified., Conclusions: A single dose of Ad26.COV2.S provided 52.9% protection against moderate to severe-critical Covid-19. Protection varied according to variant; higher protection was observed against severe Covid-19, medical intervention, and death than against other end points and lasted for 6 months or longer. (Funded by Janssen Research and Development and others; ENSEMBLE ClinicalTrials.gov number, NCT04505722.)., (Copyright © 2022 Massachusetts Medical Society.)

Background and Objectives: Cerebral venous sinus thrombosis (CVST) as a part of the thrombosis and thrombocytopenia syndrome is a rare adverse drug reaction of severe acute respiratory syndrome coronavirus disease 2 (SARS-CoV-2) vaccination. Estimated background rate of CVST with thrombocytopenia is 0.1 per million per month. We assessed the age-stratified risk of CVST with and without thrombocytopenia after SARS-CoV-2 vaccination., Methods: We estimated the absolute risk of CVST with and without thrombocytopenia within 28 days of a first dose of 4 SARS-CoV-2 vaccinations using data from the European Medicines Agency's EudraVigilance database (until June 13, 2021). As a denominator, we used data on vaccine delivery from 31 European countries. For 22.8 million adults from 25 countries, we estimated the absolute risk of CVST after the first dose of ChAdOx1 nCov-19 per age category., Results: The absolute risk of CVST within 28 days of first-dose vaccination was 7.5 (95% confidence interval [CI] 6.9-8.3), 0.7 (95% CI 0.2-2.4), 0.6 (95% CI 0.5-0.7), and 0.6 (95% CI 0.3-1.1) per million of first doses of ChAdOx1 nCov-19, Ad26.COV2.S, BNT162b2, and mRNA-1273, respectively. The absolute risk of CVST with thrombocytopenia within 28 days of first dose vaccination was 4.4 (95% CI 3.9-4.9), 0.7 (95% CI 0.2-2.4), 0.0 (95% CI 0.0-0.1), and 0.0 (95% CI 0.0-0.2) per million of first doses of ChAdOx1 nCov-19, Ad26.COV2.S, BNT162b2, and mRNA-1273, respectively. In recipients of ChAdOx1 nCov-19, the absolute risk of CVST, both with and without thrombocytopenia, was the highest in the 18- to 24-year-old group (7.3 per million, 95% CI 2.8-18.8 and 3.7 per million, 95% CI 1.0-13.3, respectively). The risk of CVST with thrombocytopenia in ChAdOx1 nCov-19 recipients was the lowest in the age group ≥70 years (0.2, 95% CI 0.0-1.3). Age <60 years compared to ≥60 years was a predictor for CVST with thrombocytopenia (incidence rate ratio 5.79, 95% CI 2.98-11.24, p < 0.001)., Discussion: The risk of CVST with thrombocytopenia within 28 days of first-dose vaccination with ChAdOx1 nCov-19 was higher in younger age groups. The risk of CVST with thrombocytopenia was slightly increased in patients receiving Ad26.COV2.S compared with the estimated background risk. The risk of CVST with thrombocytopenia was not increased in recipients of SARS-CoV-2 mRNA vaccines., (© 2021 American Academy of Neurology.)

Currently, the world is coping with the COVID-19 pandemic with a few vaccines. So far, the European Medicine Agency has approved four of them. However, following widespread vaccination with the recombinant adenoviral vector-based Oxford-AstraZeneca vaccine, available only in the United Kingdom and Europe, many concerns have emerged, especially the report of several cases of the otherwise rare cerebral sinus vein thrombosis and splanchnic vein thrombosis. The onset of thrombosis particularly at these unusual sites, about 5--14 days after vaccination, along with thrombocytopenia and other specific blood test abnormalities, are the main features of the vaccine side effects. The acronym vaccine-induced prothrombotic immune thrombocytopenia (VIPIT) has been coined to name this new condition, with the aim of highlighting the difference from the classic heparin-induced thrombocytopenia (HIT). VIPIT seems to primarily affect young to middle-aged women. For this reason, the vaccine administration has been stopped or limited in a few European countries. Coagulopathy induced by the Oxford-AstraZeneca vaccine (and probably by Janssen/Johnson & Johnson vaccine as well in the USA) is likely related to the use of recombinant vector DNA adenovirus, as experimentally proven in animal models. Conversely, Pfizer and Moderna vaccines use mRNA vectors. All vaccine-induced thrombotic events should be treated with a nonheparin anticoagulant. As the condition has some similarities with HIT, patients should not receive any heparin or platelet transfusion, as these treatments may potentially worsen the clinical course. Aspirin has limited rational use in this setting and is not currently recommended. Intravenous immunoglobulins may represent another potential treatment, but, most importantly, clinicians need to be aware of this new unusual postvaccination syndrome., (Copyright © 2021 Italian Federation of Cardiology - I.F.C. All rights reserved.)

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a newly described hematologic disorder, which presents as acute thrombocytopenia and thrombosis after administration of the ChAdOx1 nCov-19 (AstraZeneca) and Ad26.COV2.S (Johnson & Johnson) adenovirus-based vaccines against COVID-19. Due to positive assays for antibodies against platelet factor 4 (PF4), VITT is managed similarly to autoimmune heparin-induced thrombocytopenia (HIT) with intravenous immunoglobulin (IVIG) and non-heparin anticoagulation. We describe a case of VITT in a 50-year-old man with antecedent alcoholic cirrhosis who presented with platelets of 7 × 10 3 /μL and portal vein thrombosis 21 days following administration of the Ad26.COV2.S COVID-19 vaccine. The patient developed progressive thrombosis and persistent severe thrombocytopenia despite IVIG, rituximab and high-dose steroids and had persistent anti-PF4 antibodies over 30 days after his initial presentation. As such, delayed therapeutic plasma exchange (TPE) was pursued on day 32 of admission as salvage therapy, with a sustained improvement in his platelet count. Our case serves as proof-of-concept of the efficacy of TPE in VITT., (© 2021 Wiley Periodicals LLC.)

On February 27, 2021, the Food and Drug Administration (FDA) issued an Emergency Use Authorization (EUA) for the adenovirus-vectored COVID-19 vaccine (Janssen Biotech, Inc., a Janssen Pharmaceutical company, Johnson & Johnson), and on February 28, 2021, the Advisory Committee on Immunization Practices (ACIP) issued an interim recommendation for its use as a single-dose primary vaccination in persons aged ≥18 years (1,2). On April 13, 2021, CDC and FDA recommended a pause in the use of Janssen COVID-19 vaccine after reports of thrombosis with thrombocytopenia syndrome (TTS), a rare condition characterized by low platelets and thrombosis, including at unusual sites such as the cerebral venous sinus (cerebral venous sinus thrombosis [CVST]), after receipt of the vaccine.* ACIP rapidly convened two emergency meetings to review reported cases of TTS, and 10 days after the pause commenced, ACIP reaffirmed its interim recommendation for use of the Janssen COVID-19 vaccine in persons aged ≥18 years, but included a warning regarding rare clotting events after vaccination, primarily among women aged 18-49 years (3). In July, after review of an updated benefit-risk assessment accounting for risks of Guillain-Barré syndrome (GBS) and TTS, ACIP concluded that benefits of vaccination with Janssen COVID-19 vaccine outweighed risks. Through ongoing safety surveillance and review of reports from the Vaccine Adverse Event Reporting System (VAERS), additional cases of TTS after receipt of Janssen COVID-19 vaccine, including deaths, were identified. On December 16, 2021, ACIP held an emergency meeting to review updated data on TTS and an updated benefit-risk assessment. At that meeting, ACIP made a recommendation for preferential use of mRNA COVID-19 vaccines over the Janssen COVID-19 vaccine, including both primary and booster doses administered to prevent COVID-19, for all persons aged ≥18 years. The Janssen COVID-19 vaccine may be considered in some situations, including for persons with a contraindication to receipt of mRNA COVID-19 vaccines., Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. Allison Lale reports personal fees from the Medical Library Association, outside the submitted work. No other potential conflicts of interest were disclosed.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in pregnancy is associated with a higher risk for severe morbidity and mortality when compared with infection in non-pregnant women of childbearing age. An increasing number of countries recommend immunization against SARS-CoV-2 in pregnant women. Recent studies provide preliminary and supportive evidence on safety, immunogenicity and effectiveness of coronavirus disease 2019 (COVID-19) vaccines in pregnant women; however, important knowledge gaps remain which warrant further studies. This collaborative consensus paper provides a review of the current literature on COVID-19 vaccines in pregnant women, identifies knowledge gaps and outlines priorities for future research to optimize protection against SARS-CoV-2 in the pregnant women and their infants., Competing Interests: SE: Research support from GSK, Sanofi and Vifor. Speaker’s fees from GSK, Pfizer, Novartis, Sanofi Pasteur and MSD in the past three years. BA is supported by Michael Smith Health Research BC. MO’R: Received research funding for Phase III Covid-19 vaccine trial from Janssen; Received research funding for Phase II Pneumococcal conjugate vaccine trial from Pfizer. VD-B: no conflict of interest to declare. SM: Institution received funding on COVID-19 from BMGF, South African Medical Research Council and Novavax. Also, participating in clinical trials of Pfizer/Biontech and JJ Covid-19 vaccines in pregnant women. MS is a member of the data safety and monitoring board for Janssen and CEPI and received research grants and/or consultancy fees from Astra Zeneca, Janssen, Pfizer, Sanofi, Seqirus, Takeda, MSD and GSK. KF is a member of the Australian Technical Advisory Group on Immunisation noting that this paper represents her own personal view; received honoraria as a member of the vaccine advisory boards for Seqiris and Sanofi Pasteur in the last 5 years. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Abu-Raya, Madhi, Omer, Amirthalingam, Giles, Flanagan, Zimmermann, O’Ryan, Safadi, Papaevangelou, Maertens, Wanlapakorn, Diaz-Brito, Tommelein and Esposito.)

Although much less common than deep vein thrombosis of the lower extremities or lungs, clots in unusual locations, including the splanchnic, cerebral, retinal, upper-extremity, and renal locations, present with significant morbidity and mortality. In the last 2 decades, treatment of clots in these unusual locations is primarily managed medically, with interventional and surgical approaches reserved for more severe or refractory cases. The hematologist is well positioned to provide consultation to organ-specific specialties (ie, neurosurgery, hepatology, ophthalmology), especially because acquired and congenital hypercoagulability plays a major role, and anticoagulation is often the primary treatment. Historically, treatment has been based on expert opinion, but systematic reviews and meta-analyses have recently been published. Various societies have produced guidelines for the treatment of clots in unusual locations; however, randomized clinical trial data remain scarce. In the last few years, increasing data have emerged concerning the efficacy of the direct oral anticoagulants in treating clots in unusual locations. Cases have recently been described highlighting atypical thrombosis associated with COVID-19 infection as well as with the ChAdOx1 nCoV-19 (AstraZeneca) vaccine and Johnson and Johnson's Janssen Ad26.COV2.S vaccine. This article reviews clots in unusual locations with an emphasis on the splanchnic (mesenteric, portal, splenic, hepatic) and cerebral circulation. Through a case-based approach, key questions are posed, and data are presented to help guide diagnosis and treatment., (Copyright © 2021 by The American Society of Hematology.)

Importance: Little is known about the factors associated with COVID-19 vaccine adverse effects in a real-world population., Objective: To evaluate factors potentially associated with participant-reported adverse effects after COVID-19 vaccination., Design, Setting, and Participants: The COVID-19 Citizen Science Study, an online cohort study, includes adults aged 18 years and older with a smartphone or internet access. Participants complete daily, weekly, and monthly surveys on health and COVID-19-related events. This analysis includes participants who provided consent between March 26, 2020, and May 19, 2021, and received at least 1 COVID-19 vaccine dose., Exposures: Participant-reported COVID-19 vaccination., Main Outcomes and Measures: Participant-reported adverse effects and adverse effect severity. Candidate factors in multivariable logistic regression models included age, sex, race, ethnicity, subjective social status, prior COVID-19 infection, medical conditions, substance use, vaccine dose, and vaccine brand., Results: The 19 586 participants had a median (IQR) age of 54 (38-66) years, and 13 420 (68.8%) were women. Allergic reaction or anaphylaxis was reported in 26 of 8680 participants (0.3%) after 1 dose of the BNT162b2 (Pfizer/BioNTech) or mRNA-1273 (Moderna) vaccine, 27 of 11 141 (0.2%) after 2 doses of the BNT162b2 or mRNA-1273 vaccine or 1 dose of the JNJ-78436735 (Johnson & Johnson) vaccine. The strongest factors associated with adverse effects were vaccine dose (2 doses of BNT162b2 or mRNA-1273 or 1 dose of JNJ-78436735 vs 1 dose of BNT162b2 or mRNA-1273; odds ratio [OR], 3.10; 95% CI, 2.89-3.34; P < .001), vaccine brand (mRNA-1273 vs BNT162b2, OR, 2.00; 95% CI, 1.86-2.15; P < .001; JNJ-78436735 vs BNT162b2: OR, 0.64; 95% CI, 0.52-0.79; P < .001), age (per 10 years: OR, 0.74; 95% CI, 0.72-0.76; P < .001), female sex (OR, 1.65; 95% CI, 1.53-1.78; P < .001), and having had COVID-19 before vaccination (OR, 2.17; 95% CI, 1.77-2.66; P < .001)., Conclusions and Relevance: In this real-world cohort, serious COVID-19 vaccine adverse effects were rare and comparisons across brands could be made, revealing that full vaccination dose, vaccine brand, younger age, female sex, and having had COVID-19 before vaccination were associated with greater odds of adverse effects. Large digital cohort studies may provide a mechanism for independent postmarket surveillance of drugs and devices.

The ChAdOx1 nCoV-19 (ChA) (AstraZeneca) and Ad26.COV2.S (AD26) (Janssen) vaccines are virus-based coronavirus disease 2019 (COVID-19) vaccines used worldwide. In spring 2021, venous blood clots and thrombocytopenia were described in some vaccine recipients. We evaluated the frequency of severe adverse events (SAEs) documented in the EudraVigilance European database in young adult (18-64 years old) and older (≥65 years old) vaccine recipients up to 23 June 2021 and related them to coagulation disorders and arterial, cardiac, and nervous system events. Comparison between the frequency of SAEs and SAE-related deaths in ChA and AD26 vs. BNT162b2 COVID-19 (BNT) (Pfizer/BioNTech) vaccine recipients demonstrated: 1) ChA and AD26 recipients than BNT recipients had higher frequencies of not only SAEs caused by venous blood clots and hemorrhage, but also thromboembolic disease and arterial events, including myocardial infarction and stroke; 2) a corresponding higher frequency of SAE-related deaths. The frequency was higher in both young adults and older adults. Comparison between the frequency of SAEs and SAE-related deaths in AD26 vs. ChA recipients demonstrated in AD26 recipients: 1) lower frequency of thrombocytopenia; 2) lower frequency of SAEs in young adult recipients; 3) higher frequency of SAEs in older recipients. Interestingly, most of the venous thrombotic SAEs associated with ChA and AD26 vaccines were not associated with thrombocytopenia, suggesting that TTS (thrombosis with thrombocytopenia syndrome) is not the only type of thrombosis observed following virus-based vaccines. In conclusion, both virus-based COVID-19 vaccines show more SAEs than BNT, but the frequency of the SAE type in the different age groups differs, suggesting that the mechanisms responsible of SAEs overlap only partly., (Copyright © 2021 Elsevier Ltd. All rights reserved.)