Seroprevalence of SARS-CoV-2 IgG Antibodies in Utsunomiya City, Greater Tokyo, after first pandemic in 2020 (U-CORONA): a household- and population-based study

Abstract

Background: The number of confirmed cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in Japan are substantially lower in comparison to the US and UK, potentially due to the under-implementation of polymerase chain reaction (PCR) tests. Studies reported that more than half of the SARS-CoV-2 infections are asymptomatic, confirming the importance for conducting seroepidemiological studies. Although the seroepidemiological studies in Japan observed a reported prevalence of 0.10% in Tokyo, 0.17% in Osaka, and 0.03% in Miyagi, sampling bias was not considered. The study objective was to assess the seroprevalence of SARS-CoV-2 in a random sample of households in Utsunomiya City in Tochigi Prefecture, Greater Tokyo, Japan. Methods: We launched the Utsunomiya COVID-19 seROprevalence Neighborhood Association (U-CORONA) Study to assess the seroprevalence of COVID-19 in Utsunomiya City. The survey was conducted between 14 June 2020 and 5 July 2020, in between the first and second wave of the pandemic. Invitations enclosed with a questionnaire were sent to 2,290 people in 1,000 households randomly selected from Utsunomiya basic resident registry. Written informed consent was obtained from all participants. The level of IgG antibodies to SARS-CoV-2 was assessed by chemiluminescence immunoassay analysis. Results: Among 2,290 candidates, 753 returned the questionnaire and 742 received IgG tests (32.4 % participation rate). Of the 742 participants, 86.8% were 18 years or older, 52.6% were women, 71.1% were residing within 10 km from the test clinic, and 89.2% were living with another person. The age and sex distribution, distance to clinic and police district were similar with those of non-participants, while the proportion of single-person households was higher among non-participants than participants (16.2% vs. 10.8%). We confirmed three positive cases through quantitative antibody testing. No positive cases were found among the people who live in the same household as someone with positive. All cases were afebrile. The estimated unweighted and weighted prevalence of SARS-CoV-2 infection were 0.40% (95% confidence interval: 0.08-1.18%) and 1.23% (95% confidence interval: 0.17-2.28%), respectively. Conclusion: This study suggests the importance of detecting all cases using PCR or antigen testing, not only at a hospital, but also in areas where people assemble. Further prospective studies using this cohort are needed to monitor SARS-CoV-2 antibody levels.

Susceptibility to SARS-CoV-2 Infection Among Children and Adolescents Compared With Adults

“…A total of 18 studies were contact-tracing studies (CTSs), 7,10,12,16-31 with 3 based in schools, [29][30][31] and 14 studies were population screening studies. 7, [32][33][34][35][36][37][38][39][40][41][42][43][44][45] Two were high quality, 33,35 22 were medium quality, 10,12,16,21,22,[24][25][26][27][29][30][31][32]34,36,38,[40][41][42][43][44][45] 7 were low quality, [17][18][19][20]23,28,39 and 1 was uncertain quality. 7,37…”

“…Data from prevalence studies for children and adolescents compared with adults are shown in Figure 4. 7, [32][33][34][35][36][38][39][40][41][42][43][44][45] We did not undertake a meta-analysis of population screening studies given the important differences in the populations, epidemic time points, and methodologies involved.…”

“…35 A total of 10 studies reported seroprevalence, 7,36,38-45 3 being nationally representative. 7,36,38 A lower seroprevalence was identified in children and in some adolescents compared with adults in a number of studies, including a nationally representative study in Spain (ENE-COVID), 36 a Dutch nationally representative study (PIENTER Corona study), 7,37 and city or regional studies from Iran, 39 the US, 40 Switzerland, 41 and Japan, 42 although no difference by age was found in a survey in 133 sentinel cities in 26 Brazilian states. 38 Two community-based studies following localized outbreaks found lower seroprevalence among children and adolescents than adults in Lombardy, Italy, 43 and Thuringia, Germany, 44 with a second German postoutbreak study 45 finding no overall association with age.…”

Interplay between social isolation and loneliness and chronic systemic inflammation during the COVID-19 pandemic in Japan: Results from U-CORONA study

“…The current study used data from the “Utsunomiya COVID-19 seROprevalence Neighborhood Association (U-CORONA)” study initiated to assess the seroprevalence of COVID-19 in Utsunomiya City, Japan ( Nawa et al, 2020 ). The survey was conducted from 14 th June 2020 to 5 th July 2020, after the first but before the second wave of outbreak in Japan.…”

SARS-CoV-2 seroprevalence among healthcare workers in general hospitals and clinics in Japan

“…In Japan, the confirmed cases of COVID-19 remained low as of December 2020 compared with those in Europe or northern America. The low seroprevalence (0.03%-0.40%) of COVID-19 in the general population of Japan was reported in several studies conducted from June to September 2020 (1). However, the prevalence of COVID-19 among healthcare workers in Japan, who are at higher risk for COVID-19 infection (2), is not well characterized.…”