Two-Year Seroprevalence Surveys of SARS-CoV-2 Antibodies among Outpatients and Healthcare Workers in Ehime, Japan

Suemori, Koichiro; Taniguchi, Yumi; Okamoto, Ai; Murakami, Akiko; Ochi, Fumihiro; Aono, Harutaka; Hato, Naohito; Osawa, Haruhiko; Miyamoto, Hitoshi; Sugiyama, Takashi; Yamashita, Masakatsu; Tauchi, Hisamichi; Takenaka, Katsuto

doi:10.7883/yoken.jjid.2022.155

Cited by 2 publications

(2 citation statements)

References 15 publications

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“…We examined the time course of seroprevalence of antibodies against SARS-CoV-2 by age group by analyzing >60,000 samples from Japan over a 25-month period. In addition to previous studies (18,19), our study expands knowledge about SARS-CoV-2 seroprevalence in the country. Diagnostic testing to identify persons infected with SARS-CoV-2 is important for gaining a better understanding of the epidemiologic situation of COVID-19.…”

Section: Discussionmentioning

confidence: 52%

Age-Stratified Seroprevalence of SARS-CoV-2 Antibodies before and during the Vaccination Era, Japan, February 2020–March 2022

Yamayoshi¹,

Iwatsuki‐Horimoto²,

Okuda³

et al. 2022

Emerg. Infect. Dis.

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despite the development of effective vaccines and therapeutics, >500 million persons had been infected with the virus and ≈6 million had died (1). In Japan, with a population of ≈125 million, the reported numbers are ≈7 million infections and ≈30,000 deaths by that time (2); however, the actual number of infected persons must be higher than the reported figure because not all infected persons undergo diagnostic testing.A serologic survey can retrospectively find persons who have been infected with the virus (3). Antibodies against the SARS-CoV-2 spike protein are generated by vaccination and natural infection. In contrast, antibodies against other components of the virus, such as the nucleoprotein, represent a history of SARS-CoV-2 natural infection but not vaccination with the COVID-19 vaccines currently available in Japan. Analyses of seroprevalence in several countries have revealed that the actual incidence of SARS-CoV-2 infection is much higher than the reported COVID-19 cases (3). For example, in the United States, the seroprevalence of antibodies against the SARS-CoV-2 nucleoprotein ranged from 3% to 10% in 2020 (4-7), and this number reached roughly 20%-60% in 2021 (8,9). However, diagnostic tests confirmed only a Age-Stratified Seroprevalence of SARS-CoV-2 Antibodies before and during the Vaccination Era, Japan,

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Section: Discussionmentioning

confidence: 52%

Age-Stratified Seroprevalence of SARS-CoV-2 Antibodies before and during the Vaccination Era, Japan, February 2020–March 2022

Yamayoshi¹,

Iwatsuki‐Horimoto²,

Okuda³

et al. 2022

Emerg. Infect. Dis.

View full text Add to dashboard Cite

show abstract

“…The present study investigated the time course of seroprevalence of antibodies against SARS-CoV-2 by age group, analyzing over 60,000 samples from Japan. Although several previous studies have reported SARS-CoV-2 seroprevalence in Japan (18,19), our study is the largest to collect samples from a wide area over a period of 25 months. Diagnostic testing to identify SARS-CoV-2-infected people is important for gaining a better understanding of the epidemiological situation of COVID-19; however, it is virtually impossible to contain the epidemic through testing alone (20).…”

Section: Discussionmentioning

confidence: 99%

Age-stratified seroprevalence of antibodies against SARS-CoV-2 in the pre- and post-vaccination era, February 2020–March 2022, Japan

Yamayoshi

Iwatsuki‐Horimoto

Okuda

et al. 2022

Preprint

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Japan has reported a small number of COVID-19 cases relative to other countries. Because not all infected people receive diagnostic tests for COVID-19, the reported number of COVID-19 cases must be lower than the actual number of infections. Assessments of the presence of antibodies against the spike protein of SARS-CoV-2 can retrospectively determine the history of natural infection and vaccination. In this study, we assessed SARS-CoV-2 seroprevalence by analyzing over 60,000 samples collected in Japan from February 2020 to March 2022. The results showed that about 5% of the Japanese population had been infected with the virus by January 2021. The seroprevalence increased with the administration of vaccinations to adults; however, among the elderly, it was not as high as the vaccination rate, probably due to poor immune responses to the vaccines and waning immunity. The infection was spread during the epidemic waves caused by the SARS-CoV-2 Delta and Omicron variants among children who were not eligible for vaccination. Nevertheless, their seroprevalence was as low as 10% as of March 2022. Our study underscores the low incidence of SARS-CoV-2 infection in Japan and the effects of vaccination on immunity at the population level.

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Two-Year Seroprevalence Surveys of SARS-CoV-2 Antibodies among Outpatients and Healthcare Workers in Ehime, Japan

Cited by 2 publications

References 15 publications

Age-Stratified Seroprevalence of SARS-CoV-2 Antibodies before and during the Vaccination Era, Japan, February 2020–March 2022

Age-Stratified Seroprevalence of SARS-CoV-2 Antibodies before and during the Vaccination Era, Japan, February 2020–March 2022

Age-stratified seroprevalence of antibodies against SARS-CoV-2 in the pre- and post-vaccination era, February 2020–March 2022, Japan

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