Antibody seroprevalence in the epicenter Wuhan, Hubei, and six selected provinces after containment of the first epidemic wave of COVID-19 in China

Abstract

Background China implemented containment measures to stop SARS-CoV-2 transmission in response to the COVID-19 epidemic. After the first epidemic wave, we conducted population-based serological surveys to determine extent of infection, risk factors for infection, and neutralization antibody levels to assess the real infections in the random sampled population. Methods We used a multistage, stratified cluster random sampling strategy to conduct serological surveys in three areas - Wuhan, Hubei Province outside Wuhan, and six provinces selected on COVID-19 incidence and containment strategy. Participants were consenting individuals >1 year old who resided in the survey area >14 days during the epidemic. Provinces screened sera for SARS-CoV-2-specific IgM, IgG, and total antibody by two lateral flow immunoassays and one magnetic chemiluminescence enzyme immunoassay; positive samples were verified by micro-neutralization assay. Findings We enrolled 34,857 participants (overall response rate, 92%); 427 were positive by micro-neutralization assay. Wuhan had the highest weighted seroprevalence (4•43%, 95% confidence interval [95%CI]=3•48%-5•62%), followed by Hubei-ex-Wuhan (0•44%, 95%CI=0•26%-0•76%), and the other provinces (<0•1%). Living in Wuhan (adjusted odds ratio aOR=13•70, 95%CI= 7•91–23•75), contact with COVID-19 patients (aOR=7•35, 95%CI=5•05–10•69), and age over 40 (aOR=1•36, 95%CI=1•07–1•72) were significantly associated with SARS-CoV-2 infection. Among seropositives, 101 (24%) reported symptoms and had higher geometric mean neutralizing antibody titers than among the 326 (76%) without symptoms (30±2•4 vs 15±2•1, p <0•001). Interpretation The low overall extent of infection and steep gradient of seropositivity from Wuhan to the outer provinces provide evidence supporting the success of containment of the first wave of COVID-19 in China. SARS-CoV-2 infection was largely asymptomatic, emphasizing the importance of active case finding and physical distancing. Virtually the entire population of China remains susceptible to SARS-CoV-2; vaccination will be needed for long-term protection. Funding This study was supported by the Ministry of Science and Technology (2020YFC0846900) and the National Natural Science Foundation of China (82041026, 82041027, 82041028, 82041029, 82041030, 82041032, 82041033).

COVID-19 in children and the importance of COVID-19 vaccination

“…Therefore, relying on hospitalization or testing rates alone underestimates the true disease burden [ 6 , 7 ]. Li et al found that the SARS-CoV-2 infection rate of children at the early stage of the epidemic in Wuhan was 2.4%–3.1%, with the overall infection rate of 4.4% [ 8 ]. Subsequent studies have shown consistently that children and adolescents are as likely to be infected as the adult population [ 9 – 11 ].…”

COVID-19 vaccination program in the mainland of China: a subnational descriptive analysis on target population size and current progress

“…The secondary goal is to protect the high-risk population, which is more vulnerable to severe clinical illness once infected, including people with underlying conditions and older adults 60 years of age or above [11,13]. Considering variations in the risk of severe outcomes given SARS-CoV-2 infection across age groups [14,15], we further categorized the target population into (1) individuals aged 60 or over at least one underlying condition; (2) The tertiary goal is to contain SARS-CoV-2 transmission, and thus the target population includes other individuals under 60 years of age without underlying conditions, i.e., working-age people (18-59 years), school-aged children (6-17 years) and younger children (0-5 years) [11,13]. The detailed definition of priority groups is presented in Additional file 1: Table S1.…”

“…Author details 1 Shanghai Institute of Infectious Disease and Biosecurity, School of Public Health, Fudan University, Shanghai, China. 2 Key Laboratory of Public Health Safety, Ministry of Education, Fudan University, Shanghai, China. 3 Department of Infectious Diseases, Huashan Hospital, Fudan University, Shanghai, China.…”

“…almost the entire population is still susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) [2], China is facing substantial risks of both imported COVID-19 cases and a domestic resurgence in the long run, with over 20 outbreaks of varying scales (from dozens to hundreds of COVID-19 cases reported) occurring frequently in the past year [3]. Relying on stringent NPIs, such as citywide nucleic acid testing and travel restriction [4][5][6], these local outbreaks were quickly contained.…”

Seroprevalence of SARS-CoV-2 antibodies in Seattle, Washington: October 2019–April 2020

“…antibody positivity in parts of the world that had more cases early on in the pandemic, including other parts of the United States (3.2-6.9%) [9], Wuhan, China (4.4%) [15], Spain (4.6%) [16], Geneva (4.8%) [17], Ariano Irpino, Italy (5.6%) [18], and northern Iran (22.2%) [19].…”