Abstract
BackgroundTokyo, the capital of Japan, is a densely populated city of >13 million people, so the population is at high risk of epidemic severe acute respiratory coronavirus 2 (SARS-CoV-2) infection. A serologic survey of anti–SARS-CoV-2 IgG would provide valuable data for assessing the city’s SARS-CoV-2 infection status. Therefore, this cross-sectional study estimated the anti–SARS-CoV-2 IgG seroprevalence in Tokyo.MethodsLeftover serum of 23,234 hospital visitors was tested for antibodies against SARS-CoV-2 using an iFlash 3000 chemiluminescence immunoassay analyzer (Shenzhen YHLO Biotech, Shenzhen, China) with an iFlash–SARS-CoV-2 IgG kit (YHLO) and iFlash–SARS-CoV-2 IgG-S1 kit (YHLO). Serum samples with a positive result (≥10 AU/mL) in either of these assays were considered seropositive for anti–SARS-CoV-2 IgG. Participants were randomly selected from patients visiting 14 Tokyo hospitals between September 1, 2020 and March 31, 2021. No participants were diagnosed with coronavirus disease 2019 (COVID-19), and none exhibited COVID-19-related symptoms at the time of blood collection.ResultsThe overall anti–SARS-CoV-2 IgG seroprevalence among all participants was 1.83% (95% confidence interval [CI], 1.66–2.01%). The seroprevalence in March 2021, the most recent month of this study, was 2.70% (95% CI, 2.16–3.34%). After adjusting for population age, sex, and region, the estimated seroprevalence in Tokyo was 3.40%, indicating that 470,778 individuals had a history of SARS-CoV-2 infection.ConclusionsThe estimated number of individuals in Tokyo with a history of SARS-CoV-2 infection was 3.9-fold higher than the number of confirmed cases. Our study enhances understanding of the SARS-CoV-2 epidemic in Tokyo.
Highlights
Coronavirus disease 2019 (COVID-19), a flu-like illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV2), emerged in Central China in late 2019 and rapidly spread worldwide
None of the participants had a previous diagnosis of COVID-19, and no participants exhibited any COVID-19-related symptoms at the time of blood collection
By the end of March 2021, a total of 120,986 patients in Tokyo had been diagnosed with SARS-CoV2 infection using reverse transcription-polymerase chain reaction (RT-PCR) or antigen testing in Tokyo; the estimated number of Tokyo residents infected with SARS-CoV-2 was 3.9-fold higher than the number of confirmed cases, which suggests that 74.3% of infections were undiagnosed
Summary
Coronavirus disease 2019 (COVID-19), a flu-like illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV2), emerged in Central China in late 2019 and rapidly spread worldwide. Seroprevalence of Anti–SARS-CoV-2 IgG in Tokyo, 2020–2021 contrast to severe cases, many SARS-CoV-2 infections are asymptomatic.[3] these patients exhibit no clinical symptoms or signs, viral RNA can be detected in samples of saliva or nasopharyngeal and throat swabs. Both symptomatic and asymptomatic patients can potentially transmit the virus to others; the ability to identify asymptomatic patients would aid in controlling COVID-19. A serologic survey of anti–SARS-CoV-2 IgG would provide valuable data for assessing the city’s SARS-CoV-2 infection status. This cross-sectional study estimated the anti–SARS-CoV-2 IgG seroprevalence in Tokyo
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