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

Abstract

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.

Impact of Omicron-Variant SARS-CoV-2 Infection on Depression and Anxiety: A Community-Based Study in Korea

“…Coronaviruses can cause psychopathological effects through two pathways: direct viral infection of the central nervous system or indirect effects via immune response [ 27 ]. Considering the relatively mild nature of the Omicron variant [ 28 ], there may have been a smaller biological inflammatory response, leading to a potentially reduced effect on depression and anxiety levels. This is consistent with a previous study conducted on SARS-CoV-2 infected inpatients, where patients with Omicron variant infection exhibited decreased depression and anxiety symptoms [ 29 ].…”

The Course of COVID-19 and Long COVID: Identifying Risk Factors among Patients Suffering from the Disease before and during the Omicron-Dominant Period

“…On the other hand, patients of the Omicron-dominant period were more likely to complain about coughing. A systematic review by Arabi et al concluded that the Omicron variant is less severe, with a related pandemic wave reporting lower rates of hospitalization, intensive care unit admissions, deaths, and patients needing oxygenation/ventilation [ 34 ]. Other studies performed in Poland complemented these findings, indicating that the Delta variant is associated with a more severe disease course and a higher risk of death relative to Omicron [ 3 , 35 ].…”

“…Since most cells of the throat and nose lack this protein, Omicron invades them via endocytosis [ 51 ]. Consequently, despite the greater transmissibility of Omicron, it infects the upper respiratory tract, while other strains infect the lower respiratory tract, making Omicron less harmful to humans [ 34 , 52 ].…”

The relative prevalence of the Omicron variant within SARS-CoV-2 infected cohorts in different countries: A systematic review

“…It was reported that patients infected with the Delta variant of the SARS-Cov-2 virus had more severe symptoms than the patients infected with the Omicron variant. 89 Vieillard-Baron et al, 19 for example, found that Omicron patients were 64% less likely to develop pneumonia than Delta patients. Ulloa et al 18 also determined that the risk of hospitalization amongst Omicron patients was reduced by 65% (compared to Delta patients), and the risk of admission to the ICU (intensive care unit) or death was reduced by 83% (compared to Delta patients).…”