Severity of the Omicron SARS-CoV-2 variant compared with the previous lineages: A systematic review.

The Omicron variant was first detected in October 2021, which evolved from the original SARS-CoV-2 strain and was found to possess many mutations. Immune evasion was one of the notable consequences of these mutations. Despite Omicron exhibiting increased transmissibility, the rates of hospitalizations and deaths among patients infected with this variant were substantially lower when compared to other strains. However, concluding that the Omicron variant is less severe than other variants of SARS-CoV-2 requires consideration of multiple factors, including the vaccination status of infected patients as well as any previous infections with other variants. This review compiled data about any reported indicators of severity in Omicron-infected patients, including studies comparing Omicron with other variants while adjusting for confounders. A comprehensive search was conducted using different databases to target any studies about Omicron. In total, 62 studies met our inclusion criteria and were included in this study. Many studies reported a significantly reduced risk of hospitalization, ICU admission, need for oxygenation/ventilation, and death in Omicron-infected patients compared to patients infected with other variants, such as Delta. Some studies, however, reported comparable severity in Omicron infected patients as to other variants emphasizing a substantial risk for severe illness. Furthermore, the COVID-19 vaccines were less effective against Omicron relative to previous lineages, except after receiving the booster dose. One study recommended vaccination during pregnancy, which may help prevent future cases of severe SARS-CoV-2 pneumonia in neonates and young infants due to the transfer of humoral response from the mother.

Effectiveness of the pre-Omicron COVID-19 vaccines against Omicron in reducing infection, hospitalization, severity, and mortality compared to Delta and other variants: A systematic review.

Despite widespread mass rollout programs, the rapid spread of the SARS-CoV-2 Omicron variant called into question the effectiveness of the existing vaccines against infection, hospitalization, severity, and mortality compared to previous variants. This systematic review summarizes and compares the effectiveness of the COVID-19 vaccines, with respect to the above outcomes in adults, children, and adolescents. A comprehensive literature search was undertaken on several databases. Only 51 studies met our inclusion criteria, revealing that the protection from primary vaccination against Omicron infection is inferior to protection against Delta and Alpha infections and wanes faster over time. However, mRNA vaccine boosters were reported to reestablish effectiveness, although to a lower extent against Omicron. Nonetheless, primary vaccination was shown to preserve strong protection against Omicron-associated hospitalization, severity, and death, even months after last dose. However, boosters provide more robust and longer-lasting protection against hospitalizations due to Omicron as compared to only primary series.

Cancer Patients and the COVID-19 Vaccines: Considerations and Challenges.

Few guidelines exist for COVID-19 vaccination amongst cancer patients, fostering uncertainty regarding the immunogenicity, safety, and effects of cancer therapies on vaccination, which this review aims to address. A literature review was conducted to include the latest articles covering the immunogenicity and safety of COVID-19 vaccination in patients with solid and hematologic cancers receiving various treatments. Lower seropositivity following vaccination was associated with malignancy (compared to the general population), and hematologic malignancy (compared to solid cancers). Patients receiving active cancer therapy (unspecified), chemotherapy, radiotherapy, and immunosuppressants generally demonstrated lower seropositivity compared to healthy controls; though checkpoint inhibition, endocrine therapy, and cyclin dependent kinase inhibition did not appear to affect seropositivity. Vaccination appeared safe and well-tolerated in patients with current or past cancer and those undergoing treatment. Adverse events were comparable to the general population, but inflammatory lymphadenopathy following vaccination was commonly reported and may be mistaken for malignant etiology. Additionally, radiation recall phenomenon was sporadically reported in patients who had received radiotherapy. Overall, while seropositivity rates were decreased, cancer patients showed capacity to generate safe and effective immune responses to COVID-19 vaccination, thus vaccination should be encouraged and hesitancy should be addressed in this population.

Neurological Immune-Related Adverse Events After COVID-19 Vaccination: A Systematic Review.

The coronavirus disease 2019 (COVID-19) pandemic has affected millions of individuals worldwide. The global scientific effort to design an effective vaccine against this virus has led to the development of several vaccine candidates. The expedited rollout of these vaccines has created some public distrust regarding the safety of these new vaccines. This review compiles clinical data from reports of diagnosed immune-related neurological events that have occurred after COVID-19 vaccine administration with the exception of those secondary to hematological abnormalities. A systematic literature search was performed, using several databases, to identify reports of postvaccination adverse neurological events. The search resulted in 18 studies that met our criteria. These studies included 61 patients who had received COVID-19 vaccines and experienced at least 1 neurological adverse effect. The most common neurological event was facial nerve palsy (50% of all events). Other less frequently reported events included the reactivation of herpes zoster, Guillain-Barre syndrome, other demyelinating diseases, and neuropathy. The underlying mechanism was hypothesized to be related to vaccine-induced type 1 interferon production leading to decreased tolerance of the myelin sheath antigens. Other hypotheses include vaccine-induced transient lymphopenia and immune dysregulation. Most of the reported events were time limited and resolved spontaneously. Given the rarity of reported neurological events compared to the total number of vaccines administered, and the similarity in the incidence of events between COVID-19 vaccines and other more common vaccines, there is little evidence to support a causal relationship between COVID-19 vaccines and adverse neurological events.

Systemic inflammation in COVID-19 patients may induce various types of venous and arterial thrombosis: A systematic review.

COVID-19 is a global pandemic with a daily increasing number of affected individuals. Thrombosis is a severe complication of COVID-19 that leads to a worse clinical course with higher rates of mortality. Multiple lines of evidence suggest that hyperinflammation plays a crucial role in disease progression. This review compiles clinical data of COVID-19 patients who developed thrombotic complications to investigate the possible role of hyperinflammation in inducing hypercoagulation. A systematic literature search was performed using PubMed, Embase, Medline and Scopus to identify relevant clinical studies that investigated thrombotic manifestations and reported inflammatory and coagulation biomarkers in COVID-19 patients. Only 54 studies met our inclusion criteria, the majority of which demonstrated significantly elevated inflammatory markers. In the cohort studies with control, D-dimer was significantly higher in COVID-19 patients with thrombosis as compared to the control. Pulmonary embolism, deep vein thrombosis and strokes were frequently reported which could be attributed to the hyperinflammatory response associated with COVID-19 and/or to the direct viral activation of platelets and endothelial cells, two mechanisms that are discussed in this review. It is recommended that all admitted COVID-19 patients should be assessed for hypercoagulation. Furthermore, several studies have suggested that anticoagulation may be beneficial, especially in hospitalized non-ICU patients. Although vaccines against SARS-CoV-2 have been approved and distributed in several countries, research should continue in the field of prevention and treatment of COVID-19 and its severe complications including thrombosis due to the emergence of new variants against which the efficacy of the vaccines is not yet clear.