Introduction The common reported adverse effects of COVID-19 vaccination consist of the injection site's local reaction followed by several non-specific flu-like symptoms. However, rare cases of vaccine-induced immune thrombotic thrombocytopenia (VITT) and cerebral venous sinus thrombosis (CVST) after viral vector vaccines (ChAdOx1 nCoV-19 vaccine, Ad26.COV2 vaccine) have been reported. Herein we systemically reviewed the reported cases of CVST and VITT following the COVID-19 vaccination. Methods This systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. We searched PubMed until May 19, 2021, and the following Keywords were used: COVID Vaccine & Neurology, AstraZeneca COVID vaccine, ChAdOx1 nCoV-19 COVID vaccine, AZD1222 COVID vaccine, Janssen COVID vaccine, Johnson & Johnson COVID vaccine, Ad26.COV2 COVID vaccine. The authors evaluated the abstracts and titles of each article for screening and inclusion. English reports about post-vaccine CVST and VITT in humans were collected. Results Until May 19, we found 877 articles with the searched terms. We found 12 articles, which overall present clinical features of 36 patients with CVST and VITT after the ChAdOx1 nCoV-19 vaccine. Moreover, two articles were noted, which present 13 patients with CVST and VITT after Ad26.COV2 vaccine. The majority of the patients were females. Symptom onset occurred within one week after the first dose of vaccination (Range 4–19 days). Headache was the most common presenting symptom. Intracerebral hemorrhage (ICH) and/or Subarachnoid hemorrhage (SAH) were reported in 49% of the patients. The platelet count of the patients was between 5 and 127 cells×109/l, PF4 IgG Assay and d-Dimer were positive in the majority of the reported cases. Among 49 patients with CVST, at least 19 patients died (39%) due to complications of CVST and VITT. Conclusion Health care providers should be familiar with the clinical presentations, pathophysiology, diagnostic criteria, and management consideration of this rare but severe and potentially fatal complication of the COVID-19 vaccination. Early diagnosis and quick initiation of the treatment may help to provide patients with a more favorable neurological outcome.

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Purpose The purpose of this study is to meta-analytically compare the effect of differentiation strategy formulation on financial and non-financial performance to explore the agency problem. Design/methodology/approach This study was conducted using a meta-analysis approach and CMA2 software. Hypotheses has been tested using cumulative effect sizes. Then, the cumulative effect sizes if some subsamples are also tested for robustness check by manipulation of circumstances. Findings Based on the findings, differentiation affects performance dimensions. However, spite of shareholders’ wealth maximization, differentiation has a smaller effect on financial performance (as the proxy of shareholders’ wealth) compared with operational performance. Meanwhile, the robustness test showed that the results in all subcategories has also confirmed, and this supports the results. Research limitations/implications The results catch attentions of shareholders to review the elements of management evaluation in the corporate governance system in a way that they focus more on stakeholders’ interests in developing differentiation strategy. Limitations of this study is firstly based on limitations of meta-analysis approach, which provide general results of relevant studies so that the local conditions of each firm should be considered in deploying implications. Originality/value Exploring the overall schema of firms (from past to present and in different research conditions) regarding the impact of differentiation strategy on performance has been the originality of this research because of potentials of meta-analysis against past field studies. This originality led to the discovery of the general confusion of firms in the development of differentiation strategy so that it emphasizes operational performance more than financial performance.