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. 2023 Dec 14;11(1):ofad614.
doi: 10.1093/ofid/ofad614. eCollection 2024 Jan.

Seroprevalence of Anti-SARS-CoV-2 Remained Extremely Low in Taiwan Until the Vaccination Program Was Implemented

Yun-Yuan Chen  1 , Min-Hui Yang  2 , Jou-Zhen Lai  2 , Jen-Wei Chen  1 , Yun-Long Wang  2 , Sheng-Tang Wei  1 , Sheng-Mou Hou  1   3 , Chien-Jen Chen  4 , Ho-Sheng Wu  2   5
Affiliations

Seroprevalence of Anti-SARS-CoV-2 Remained Extremely Low in Taiwan Until the Vaccination Program Was Implemented

Yun-Yuan Chen et al. Open Forum Infect Dis. .

Abstract

Background: The Taiwanese government made a concerted effort to contain a coronavirus disease 2019 (COVID-19) nosocomial outbreak of variant B.1.429, shortly before universal vaccination program implementation. This study aimed to investigate seroprevalence in the highest-risk regions.

Methods: Between January and February 2021, we retrieved 10 000 repository serum samples from blood donors to examine for antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid (N) and spike (S) antigens. A positive result was confirmed if anti-N and anti-S antibodies were positive. Overall, 2000 donors residing in the highest-risk district and donating blood in January 2021 were further examined for SARS-CoV-2 RNA. We estimated seroprevalence and compared the epidemic curve between confirmed COVID-19 cases and blood donors with positive antibodies or viral RNA.

Results: Twenty-one cases with COVID-19 were confirmed in the nosocomial cluster, with an incidence of 1.27/100 000 in the COVID-affected districts. Among 4888 close contacts of the nosocomial cases, 20 (0.4%) became confirmed cases during isolation. Anti-SARS-CoV-2 was detected in 2 of the 10000 blood donors, showing a seroprevalence of 2/10000 (95% CI, 0.55-7.29). None of the 2000 donors who underwent tests for SARS-CoV-2 RNA were positive. The SARS-CoV-2 infection epidemic curve was observed sporadically in blood donors compared with the nosocomial cluster.

Conclusions: In early 2021, an extremely low anti-SARS-CoV-2 seroprevalence among blood donors was observed. Epidemic control measures through precise close contact tracing, testing, and isolation effectively contained SARS-CoV-2 transmission before universal vaccination program implementation.

Keywords: SARS-CoV-2; nosocomial infection; seroprevalence; transfusion safety.

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Conflict of interest statement

Potential conflicts of interest. All authors: no reported conflicts.

Figures

Figure 1.
Figure 1.
A, Epidemic curve and containment milestones for coronavirus disease 2019 in Taiwan (Numbers were retrieved from OurWorldInData.org) [13]. B, Symptom onset date for 21 confirmed cases [5, 9] and blood donation dates for 2 donors with anti–severe acute respiratory syndrome coronavirus 2 antibodies. Abbreviations: COVID-19, coronavirus disease 2019; EUA, Emergency Use Authorization; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.
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