tetano
Editor, Senior Moderator
J Epidemiol
. 2021 Nov 13.
doi: 10.2188/jea.JE20210324. Online ahead of print.
Serologic survey of IgG against SARS-CoV-2 among hospital visitors without a history of SARS-CoV-2 infection in Tokyo, 2020-2021
Takahiro Sanada[SUP] 1 [/SUP], Tomoko Honda[SUP] 1 [/SUP], Fumihiko Yasui[SUP] 1 [/SUP], Kenzaburo Yamaji[SUP] 1 [/SUP], Tsubasa Munakata[SUP] 1 [/SUP], Naoki Yamamoto[SUP] 1 [/SUP], Makoto Kurano[SUP] 2 [/SUP], Yusuke Matsumoto[SUP] 1 [/SUP], Risa Kohno[SUP] 1 [/SUP], Sakiko Toyama[SUP] 1 [/SUP], Yoshiro Kishi[SUP] 3 [/SUP], Takuro Horibe[SUP] 3 [/SUP], Yudai Kaneko[SUP] 3 [/SUP], Mayumi Kakegawa[SUP] 3 [/SUP], Kazushige Fukui[SUP] 4 [/SUP], Takeshi Kawamura[SUP] 4 [/SUP], Wang Daming[SUP] 5 [/SUP], Chungen Qian[SUP] 6 [/SUP], Fuzhen Xia[SUP] 7 [/SUP], Fan He[SUP] 7 [/SUP], Syudo Yamasaki[SUP] 8 [/SUP], Atsushi Nishida[SUP] 8 [/SUP], Takayuki Harada[SUP] 9 [/SUP], Masahiko Higa[SUP] 1 [/SUP], Yuko Tokunaga[SUP] 1 [/SUP], Asako Takagi[SUP] 1 [/SUP], Masanari Itokawa[SUP] 10 [/SUP], Tatsuhiko Kodama[SUP] 4 [/SUP], Michinori Kohara[SUP] 1 [/SUP]
Affiliations
Abstract
Background: Tokyo, the capital of Japan, is a densely populated city of >13 million people and thus 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. This cross-sectional study therefore estimated the anti-SARS-CoV-2 IgG seroprevalence in Tokyo.
Methods: Leftover serum of 23,234 hospital visitors was tested for antibodies against SARS-CoV-2 using an iFlash 3000 chemiluminescence immunoassay analyzer (Shenzhen YHLO Biotech) 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.
Results: The 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.
Conclusions: The 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.
Keywords: COVID-19; IgG seroprevalence; SARS-CoV-2; Tokyo; hospital visitors.
. 2021 Nov 13.
doi: 10.2188/jea.JE20210324. Online ahead of print.
Serologic survey of IgG against SARS-CoV-2 among hospital visitors without a history of SARS-CoV-2 infection in Tokyo, 2020-2021
Takahiro Sanada[SUP] 1 [/SUP], Tomoko Honda[SUP] 1 [/SUP], Fumihiko Yasui[SUP] 1 [/SUP], Kenzaburo Yamaji[SUP] 1 [/SUP], Tsubasa Munakata[SUP] 1 [/SUP], Naoki Yamamoto[SUP] 1 [/SUP], Makoto Kurano[SUP] 2 [/SUP], Yusuke Matsumoto[SUP] 1 [/SUP], Risa Kohno[SUP] 1 [/SUP], Sakiko Toyama[SUP] 1 [/SUP], Yoshiro Kishi[SUP] 3 [/SUP], Takuro Horibe[SUP] 3 [/SUP], Yudai Kaneko[SUP] 3 [/SUP], Mayumi Kakegawa[SUP] 3 [/SUP], Kazushige Fukui[SUP] 4 [/SUP], Takeshi Kawamura[SUP] 4 [/SUP], Wang Daming[SUP] 5 [/SUP], Chungen Qian[SUP] 6 [/SUP], Fuzhen Xia[SUP] 7 [/SUP], Fan He[SUP] 7 [/SUP], Syudo Yamasaki[SUP] 8 [/SUP], Atsushi Nishida[SUP] 8 [/SUP], Takayuki Harada[SUP] 9 [/SUP], Masahiko Higa[SUP] 1 [/SUP], Yuko Tokunaga[SUP] 1 [/SUP], Asako Takagi[SUP] 1 [/SUP], Masanari Itokawa[SUP] 10 [/SUP], Tatsuhiko Kodama[SUP] 4 [/SUP], Michinori Kohara[SUP] 1 [/SUP]
Affiliations
- PMID: 34776499
- DOI: 10.2188/jea.JE20210324
Abstract
Background: Tokyo, the capital of Japan, is a densely populated city of >13 million people and thus 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. This cross-sectional study therefore estimated the anti-SARS-CoV-2 IgG seroprevalence in Tokyo.
Methods: Leftover serum of 23,234 hospital visitors was tested for antibodies against SARS-CoV-2 using an iFlash 3000 chemiluminescence immunoassay analyzer (Shenzhen YHLO Biotech) 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.
Results: The 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.
Conclusions: The 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.
Keywords: COVID-19; IgG seroprevalence; SARS-CoV-2; Tokyo; hospital visitors.