Publications by authors named "Brian Pui Chun Chan"

The COVID-19 pandemic has had a major impact on global health and economy, which was significantly mitigated by the availability of COVID-19 vaccines. The levels of systemic and mucosal antibodies against SARS-CoV-2 correlated with protection. However, there is limited data on how vaccine type and booster doses affect mucosal antibody response, and how the breadth of mucosal and systemic antibodies compares.

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Background: De novo amino acid substitutions (DNS) frequently emerge among immunocompromised patients with chronic SARS-CoV-2 infection. While previous studies have reported these DNS, their significance has not been systematically studied.

Methods: We performed a review of DNS that emerged during chronic SARS-CoV-2 infection.

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Autoantibodies against angiotensin-converting enzyme 2 (ACE2) are frequently reported in patients during coronavirus disease 2019 (COVID-19) with evidence for a pathogenic role in severe infection. However, little is known of the prevalence or clinical significance of ACE2 autoantibodies in late convalescence or following COVID-19 vaccination. In this study, we measured ACE2 autoantibodies in a cohort of 182 COVID-19 convalescent patients, 186 COVID-19 vaccine recipients, and 43 adolescents with post-mRNA vaccine myopericarditis using two ACE2 enzymatic immunoassays (EIAs).

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Chronic kidney disease (CKD) patients are at higher risk of severe COVID-19. Humoral and cellular immunity from prior infection or vaccination are important for protection, but the neutralizing antibody (nAb) response against SARS-CoV-2 variants is impaired. We investigated the variant-specific nAb and T cell immunity among CKD patients.

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Background: Vaccination reduces COVID-19-related hospitalization among older adults. However, how SARS-CoV-2 infection and vaccine regimens affect vaccine-elicited immunity remain unclear.

Methods: This is a cross-sectional study recruiting adults aged ≥70 years with comorbidities in Hong Kong.

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The SARS-CoV-2 Omicron variant has led to a major wave of COVID-19 in Hong Kong between January and May 2022. Here, we used seroprevalence to estimate the combined incidence of vaccination and SARS-CoV-2 infection, including subclinical infection which were not diagnosed at the acute stage. The overall seropositive rate of IgG against receptor binding domain (anti-RBD IgG) increased from 52.

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Monitoring population protective immunity against SARS-CoV-2 variants is critical for risk assessment. We hypothesize that Hong Kong's explosive Omicron BA.2 outbreak in early 2022 could be explained by low herd immunity.

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Background: SARS-CoV-2 Omicron variant evades immunity from past infection or vaccination and is associated with a greater risk of reinfection among recovered COVID-19 patients. We assessed the serum neutralizing antibody (NAb) activity against Omicron variant (Omicron NAb) among recovered COVID-19 patients with or without vaccination.

Methods: In this prospective cohort study with 135 recovered COVID-19 patients, we determined the serum NAb titers against ancestral virus or variants using a live virus NAb assay.

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Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant BA.2 sublineage has increased rapidly in Europe and Asia since January 2022. Here, we report the epidemiological and genomic analysis of a large single-source BA.

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Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can infect human and other mammals, including hamsters. Syrian (Mesocricetus auratus) and dwarf (Phodopus sp.) hamsters are susceptible to SARS-CoV-2 infection in the laboratory setting.

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The novel SARS-CoV-2 Omicron variant may increase the risk of re-infection and vaccine breakthrough infections as it possesses key mutations in the spike protein that affect neutralizing antibody response. Most studies on neutralization susceptibility were conducted using specimens from adult COVID-19 patients or vaccine recipients. However, since the paediatric population has an antibody response to SARS-CoV-2 infection that is distinct from the adult population, it is critical to assess the neutralization susceptibility of pediatric serum specimens.

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Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) omicron variant, designated as a variant of concern by the World Health Organization, carries numerous spike mutations that are known to evade neutralizing antibodies elicited by coronavirus disease 2019 (COVID-19) vaccines. A deeper understanding of the susceptibility of omicron variant to vaccine-induced neutralizing antibodies is urgently needed for risk assessment.

Methods: Omicron variant strains HKU691 and HKU344-R346K were isolated from patients using TMPRSS2-overexpressing VeroE6 cells.

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