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Seroprevalence of Unidentified SARS-CoV-2 Infection in Hong Kong During 3 Pandemic Waves.
Boon, Siaw S; Wong, Martin C S; Ng, Rita W Y; Leung, Danny T M; Chen, Zigui; Lai, Christopher K C; Ho, Wendy C S; Huang, Junjie; Wong, Barry K C; Fung, Kitty S C; Chan, Paul K S.
  • Boon SS; Department of Microbiology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
  • Wong MCS; Jockey Club School of Public Health and Primary Care, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.
  • Ng RWY; Department of Microbiology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
  • Leung DTM; Department of Chemical Pathology, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.
  • Chen Z; Department of Microbiology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
  • Lai CKC; Department of Microbiology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
  • Ho WCS; Department of Microbiology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
  • Huang J; Jockey Club School of Public Health and Primary Care, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.
  • Wong BKC; Department of Pathology, United Christian Hospital, Hong Kong, China.
  • Fung KSC; Department of Pathology, United Christian Hospital, Hong Kong, China.
  • Chan PKS; Department of Microbiology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
JAMA Netw Open ; 4(11): e2132923, 2021 11 01.
Article in English | MEDLINE | ID: covidwho-1516695
ABSTRACT
Importance Seroprevalence studies inform the extent of infection and assist evaluation of mitigation strategies for the COVID-19 pandemic.

Objective:

To estimate the prevalence of unidentified SARS-CoV-2 infection in the general population of Hong Kong. Design, Setting, and

Participants:

A prospective cross-sectional study was conducted in Hong Kong after each major wave of the COVID-19 pandemic (April 21 to July 7, 2020; September 29 to November 23, 2020; and January 15 to April 18, 2021). Adults (age ≥18 years) who had not been diagnosed with COVID-19 were recruited during each period, and their sociodemographic information, symptoms, travel, contact, quarantine, and COVID-19 testing history were collected. Main Outcomes and

Measures:

The main outcome was prevalence of SARS-CoV-2 infection. SARS-CoV-2 IgG antibodies were detected by an enzyme-linked immunosorbent assay based on spike (S1/S2) protein, followed by confirmation with a commercial electrochemiluminescence immunoassay based on the receptor binding domain of spike protein.

Results:

The study enrolled 4198 participants (2539 [60%] female; median age, 50 years [IQR, 25 years]), including 903 (22%), 1046 (25%), and 2249 (53%) during April 21 to July 7, 2020; during September 29 to November 23, 2020; and during January 15 to April 18, 2021, respectively. The numbers of participants aged 18 to 39 years, 40 to 59 years, and 60 years or older were 1328 (32%), 1645 (39%), and 1225 (29%), respectively. Among the participants, 2444 (58%) stayed in Hong Kong since November 2019 and 2094 (50%) had negative SARS-CoV-2 RNA test results. Only 170 (4%) reported ever having contact with individuals with confirmed cases, and 5% had been isolated or quarantined. Most (2803 [67%]) did not recall any illnesses, whereas 737 (18%), 212 (5%), and 385 (9%) had experienced respiratory symptoms, gastrointestinal symptoms, or both, respectively, before testing. Six participants were confirmed to be positive for anti-SARS-CoV-2 IgG; the adjusted prevalence of unidentified infection was 0.15% (95% CI, 0.06%-0.32%). Extrapolating these findings to the whole population, there were fewer than 1.9 unidentified infections for every recorded confirmed case. The overall prevalence of SARS-CoV-2 infection in Hong Kong before the roll out of vaccination was less than 0.45%. Conclusions and Relevance In this cross-sectional study of participants from the general public in Hong Kong, the prevalence of unidentified SARS-CoV-2 infection was low after 3 major waves of the pandemic, suggesting the success of the pandemic mitigation by stringent isolation and quarantine policies even without complete city lockdown. More than 99.5% of the general population of Hong Kong remain naive to SARS-CoV-2, highlighting the urgent need to achieve high vaccine coverage.
Subject(s)

Full text: Available Collection: International databases Database: MEDLINE Document Type: Article Main subject: Pandemics / Population Health / COVID-19 Testing / SARS-CoV-2 / COVID-19 Subject: Pandemics / Population Health / COVID-19 Testing / SARS-CoV-2 / COVID-19 Type of study: Diagnostic study / Observational study / Prevalence study / Risk factors / Screening study Language: English Journal: JAMA Netw Open Year: 2021

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Full text: Available Collection: International databases Database: MEDLINE Document Type: Article Main subject: Pandemics / Population Health / COVID-19 Testing / SARS-CoV-2 / COVID-19 Subject: Pandemics / Population Health / COVID-19 Testing / SARS-CoV-2 / COVID-19 Type of study: Diagnostic study / Observational study / Prevalence study / Risk factors / Screening study Language: English Journal: JAMA Netw Open Year: 2021
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