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Background: The pathogenicity and virulence of the Omicron strain have weakened significantly pathogenesis of Omicron variants. Accumulating data indicated accessory proteins play crucial roles in host immune evasion and virus pathogenesis of SARS-CoV-2. Therefore, the impact of simultaneous deletion of accessory protein ORF7a, ORF7b and ORF8 on the clinical characteristics and specific immunity in Omicron breakthrough infected patients (BIPs) need to be verified. Methods: Herein, plasma cytokines were identified using a commercial Multi-cytokine detection kit. Enzyme-linked immunosorbent assay and pseudovirus neutralization assays were utilized to determine the titers of SARS-CoV-2 specific binding antibodies and neutralizing antibodies, respectively. In addition, an enzyme-linked immunospot assay was used to quantify SARS-CoV-2 specific T cells and memory B cells. Results: A local COVID-19 outbreak was caused by the Omicron BA.2 variant, which featured a deletion of 871 base pairs (∆871 BA.2), resulting in the removal of ORF7a, ORF7b, and ORF8. We found that hospitalized patients with ∆871 BA.2 had significantly shorter hospital stays than those with wild-type (WT) BA.2. Plasma cytokine levels in both ∆871 BA.2 and WT BA.2 patients were within the normal range of reference, and there was no notable difference in the titers of SARS-CoV-2 ancestor or Omicron-specific binding IgG antibodies, neutralizing antibody titers, effector T cells, and memory B cells frequencies between ∆871 BA.2 and WT BA.2 infected adult patients. However, antibody titers in ∆871 BA.2 infected adolescents were higher than in adults. Conclusions: The simultaneous deletion of ORF7a, ORF7b, and ORF8 facilitates the rapid clearance of the BA.2 variant, without impacting cytokine levels or affecting SARS-CoV-2 specific humoral and cellular immunity in Omicron-infected individuals. [ABSTRACT FROM AUTHOR]

Little information is available for antibody levels against SARS‐CoV‐2 variants of concern induced by Omicron breakthrough infection and a third booster with an inactivated vaccine (InV) or Ad5‐nCoV in people with completion of two InV doses. Plasma was collected from InV pre‐vaccinated Omicron‐infected patients (OIPs), unvaccinated OIPs between 0 and 22 days, and healthy donors (HDs) 14 days or 6 months after the second doses of an InV and 14 days after a homogenous booster or heterologous booster of Ad5‐nCoV. Anti‐Wuhan‐, Anti‐Delta‐, and Anti‐Omicron‐receptor binding domain (RBD)‐IgG titers were detected using enzyme‐linked immunosorbent assay. InV pre‐vaccinated OIPs had higher anti‐Wuhan‐, anti‐Delta‐, and anti‐Omicron‐RBD‐IgG titers compared to unvaccinated OIPs. Anti‐Wuhan‐RBD‐IgG titers sharply increased in InV pre‐vaccinated OIPs 0–5 days postinfection (DPI), while the geometric mean titers (GMTs) of anti‐Delta‐ and anti‐Omicron‐RBD‐IgG were 3.3‐fold and 12.0‐fold lower. Then, the GMT of anti‐Delta‐ and anti‐Omicron‐RBD‐IgG increased to 35 112 and 28 186 during 11–22 DPI, about 2.6‐fold and 3.2‐fold lower, respectively, than the anti‐Wuhan‐RBD‐IgG titer. The anti‐Wuhan‐, anti‐Delta‐, and anti‐Omicron‐RBD‐IgG titers declined over time in HDs after two doses of an InV, with 25.2‐fold, 5.6‐fold, and 4.5‐fold declination, respectively, at 6 months relative to the titers at 14 days after the second vaccination. Anti‐Wuhan‐, anti‐Delta‐, and anti‐Omicron‐RBD‐IgG titers elicited by a heterologous Ad5‐nCoV booster were significantly higher than those elicited by an InV booster, comparable to those in InV pre‐vaccinated OIPs. InV and Ad5‐nCoV boosters could improve humoral immunity against Omicron variants. Of these, the Ad5‐nCoV booster is a better alternative. [ABSTRACT FROM AUTHOR]