key: cord-1012006-bj8wn9dh authors: Nakamura, A.; Sato, R.; Ando, S.; Oana, N.; Nozaki, E.; Endo, H.; Miyate, Y.; Soma, J.; Miyata, G. title: Seroprevalence of Antibodies to SARS-CoV-2 in Healthcare Workers in Non-epidemic Region: A Report from Iwate Prefecture in Japan date: 2020-06-17 journal: nan DOI: 10.1101/2020.06.15.20132316 sha: ca4a011511a6f4054f47f3e5893412284117667d doc_id: 1012006 cord_uid: bj8wn9dh Background: As of June 8, 2020, Iwate is the only one of 47 prefectures in Japan with no confirmed coronavirus disease 2019 (COVID-19) cases. Serological survey for COVID-19 antibodies is crucial in area with low prevalence as well as epidemic area when addressing health and social issues caused by COVID-19. Rapid, accurate and easy-to-use antibody tests as well laboratory-based antibody tests are necessary for confirming immunity in a given community. Methods:Serum samples from healthcare workers (n = 1,000, mean 40 {+/-} 11 years) of Iwate Prefectural Central Hospital, Iwate, Japan were tested for the prevalence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies. Two laboratory-based quantitative tests (Abbott Architect SARS-CoV-2 IgG and Roche Elecsys Anti-SARS-CoV-2 assays) and one point-of-care (POC) qualitative test (Alfa Instant-view plus COVID-19 Test) were performed simultaneously. Sensitivity and specificity were 100%, 99.6% in Abbott assay; 100%, 99.8% in Roche assay; 97.8%, 94.6% in Alfa POC test, respectively. Results:The laboratory-based quantitative tests showed positive in 4 of 1,000 samples (0.4%) (95% CI: 0.01 to 0.79): 4/1,000 (0.4%) (95% CI: 0.01 to 0.79) in Abbott; 0/1,000 (0%) in Roche. Positive samples were not detected for both Abbott and Roche assays. The POC qualitative test showed positive in 33 of 1,000 samples (3.3%) (95% CI: 2.19 to 4.41), showing higher rates than those of the laboratory-based quantitative tests. There were no samples with simultaneous positive reaction for two quantitative tests and a POC test. Conclusions: Infected COVID-2 cases were not confirmed by a retrospective serological study in healthcare workers of our hospital. The POC qualitative tests with lower specificity have the potential for higher false positive reactions than the laboratory-based quantitative tests in areas with very low prevalence of COVID-19. antibodies is crucial in area with low prevalence as well as epidemic area when addressing health and social issues caused by COVID-19. Rapid, accurate and easy-to-use antibody tests as well laboratory-based antibody tests are necessary for confirming immunity in a given community. Serum samples from healthcare workers (n = 1,000, mean 40 ± 11 years) of Iwate Prefectural Central Hospital, Iwate, Japan were tested for the prevalence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies. Two laboratory-based quantitative tests (Abbott Architect ® SARS-CoV-2 IgG and Roche Elecsys ® Anti-SARS-CoV-2 assays) and one point-of-care (POC) qualitative test (Alfa Instant-view ® plus COVID-19 Test) were performed simultaneously. Sensitivity and specificity were 100%, 99.6% in Abbott assay; 100%, 99.8% in Roche assay; 97.8%, 94.6% in Alfa POC test, respectively. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted June 17, 2020. . https://doi.org/10.1101/2020.06.15.20132316 doi: medRxiv preprint The laboratory-based quantitative tests showed positive in 4 of 1,000 samples (0.4%) (95% CI: 0.01 to 0.79): 4/1,000 (0.4%) (95% CI: 0.01 to 0.79) in Abbott; 0/1,000 (0%) in Roche. Positive samples were not detected for both Abbott and Roche assays. The POC qualitative test showed positive in 33 of 1,000 samples (3.3%) (95% CI: 2.19 to 4 .41), showing higher rates than those of the laboratory-based quantitative tests. There were no samples with simultaneous positive reaction for two quantitative tests and a POC test. Infected COVID-2 cases were not confirmed by a retrospective serological study in healthcare workers of our hospital. The POC qualitative tests with lower specificity have the potential for higher false positive reactions than the laboratory-based quantitative tests in areas with very low prevalence of COVID-19. (Abstract: 285 words) All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. RT-PCR = real-time reverse transcriptase polymerase chain reaction SARS-CoV-2 = acute respiratory syndrome coronavirus 2 All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. developed and they can be reliable as using in areas with high prevalence of COVID-19 (6) . Although they have the potential for poorly accuracy as using in area with low prevalence, the availability of them in non-epidemic area has not been well studied. Our primary endpoint was to examine the prevalence of COVID-19 of healthcare workers in All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. This was a retrospective study evaluating the prevalence of COVID-19 antibodies in healthcare workers in Iwate Prefecture Central Hospital using currently available immunoassays for detection of antibodies specific to the SARS-CoV-2 virus. Iwate All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted June 17, 2020. were read visually after 10 min. Weak signals for IgM and IgG, together or separate, were considered positive. All tests were conducted at room temperature according to each manufacturer's instruction. In this study, a serum sample showing positive for both Abbott and Roche quantitative assays was considered an infected COVID-19 case. A serum sample All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. showing positive for either Abbott or Roche assay was a non-infected case. The prevalence of COVID-19 was determined by the number of infected cases divided by the number of measured samples. Continuous variables are expressed as mean ± SD, and categorical variables as numbers and percentages. The 95% CIs for positive rates for the tests were presented in this study. Overall, serum samples from 1,000 employees (264 men, 736 women; mean age 40 ± 11 years) were analyzed in this study. Positive reactions were found in 4 of 1,000 (0.4%) (95% CI: 0.01 to 0.79) using Abbott quantitative assay; 0 of 1,000 (0%) using Roche quantitative assay. Presence of COVID-19 cases, which were defined as positive reaction to SARS-CoV-2 IgG antibodies using Abbott and Roche quantitative assays, was not confirmed. The POC qualitative test showed positive in 33 of 1,000 samples (3.3%) (95% CI: 2.19 to 4.41), showing higher rates than those of the laboratory-based quantitative tests. There were no samples with simultaneous positive reaction for two quantitative tests and a POC test. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted June 17, 2020. positive Roche assay responses. These results suggest that it seems to be early to judge the accuracy of COCID-2 prevalence using the antibody tests with low specificity even with high specificity in the area with low prevalence The COVID-19 epidemic of Japan has reached a peak on April 11, 2020 as assessed by daily infected cases, with the number of 714 cases (4). After the peak, the number of COVID-19 cases gradually decreased and returned to the early onset levels in January. As of May 30, the total number of confirmed cases was 16,650, and 891 peoples have died (4), however infectious cases of Japan are recognized to be relatively small as compared with those of other developed countries. With flattening of epidemic curve as a result of the nation adhering to staying at home and social distancing, the All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted June 17, 2020. . https://doi.org/10.1101/2020.06.15.20132316 doi: medRxiv preprint focus has been shifted to widespread testing for COVID-19 antibodies from the RT-PCR test for diagnosis of SARS-CoV-2 infection. Serological tests to detect antibodies against the SARS-CoV-2 are crucial not only for assessment of the immunity of individuals but also for the monitoring the spread of virus and social immunity. In the epicenter showing explosive growth of infected cases such as New York State, the prevalence of COVID-19 has been reported to be as high rate as 10% to 15% (9), whereas in the areas where the spread of infection has been minimized such as Santa Clara County, California, US, it has shown to be a lower rate (<1% to 3%) (10). In Japan, the positive rate of SARS-CoV-2 specific IgG antibodies was 3.3% in 1,000 outpatients visited Kobe City Medical Center General Hospital, Kobe (11); 5.9% in 202 blood samples obtained from two community clinics in Tokyo (12). According to the Ministry of Health, labor and Welfare, in order to examine the performance of five commercially available test kits, an antibody tests were conducted with donated blood collected in Tohoku region in late April, and showed that COVID-19 antibodies were detected in 2 of 500 samples, with a positive rate of 0.4% (4). These data and our results are highly suggestive of low prevalence of COVID-19 in Tohoku district compared with that in Tokyo, Osaka, and Kobe city. Iwate Prefecture has been alone among the 47 prefectures in Japan with no All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted June 17, 2020. . https://doi.org/10.1101/2020.06.15.20132316 doi: medRxiv preprint reporting COVID-19 cases since Japan has officially recorded its first case on January 2020 (5), It seems that such situation with no infected cases have never been reported for state-sized regions in other major countries. As of May 30, more than 6,000 inquiries for RT-PCR tests had been made to a local hotline for residents with possible COVID-19 symptoms; however Iwate had conducted only 730 (11.9%) tests which were the lowest level in Japan (5) . While RT-PCR tests have generally limited to symptomatic patients or patients with known exposure, Iwate had added another hurdle, requiring the tests to be approved by some medical experts until the end of April. Even though it is unclear the reason why Iwate has been skirted SARS-CoV-2, the hospitalized patients with COVID-19 symptoms including coronavirus-infected pneumonia have never been observed so far. COVID-19 cases in neighboring prefectures like Miyagi and Aomori Prefecture (4) suggest that Iwate may actually harbor SARS-CoV-2 cases but has not detected them due to a low level of tests. Our hospital is located in Morioka, the capital city in the center of Iwate Prefecture, and has given high-quality medical research and service for the people who live in this region. By means of connecting with all other clinics and hospitals by a medical network system, our hospital has played a central role for disease treatment and prevention. On April 7, the state of emergency was declared by the prime minister of Japan (13), and All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted June 17, 2020. . https://doi.org/10.1101/2020.06.15.20132316 doi: medRxiv preprint 13 the residents in Iwate were required to stay in their home. Because of difficulties in taking a blood sample as part of random sampling from residents in Iwate, we determined the COVID-19 prevalence of healthcare workers in our hospital. Moreover, it will be essential for an assessment of nosocomial infection and provide the underlying data to prevent the spread of infection, potentially leading to a second wave of COVID-19, even though infected cases have never been found in our hospital. We believe that our study will provide the data for informing epidemic models and making public policy decisions. Recently, several commercial SARS-CoV-2 immunoassays have been developed and available for assessing the immune condition of individuals. They are also essential for control of epidemic infection and making decisions of public policy. In an infectious disease model with very low prevalence, it is recommended to choose an antibody test with a very high specificity (perhaps ≥ 99.5%) resulting a high positive predictive value (14). In this study, two laboratory-based quantitative tests with a specificity of 99.5% or more (99.6% in Abbott assay; 99.8% in Roche assay) were used, positive results were detected in 4 (0.4%) samples in the former while no positive results in the later. As was expected, there were relatively more false positive COVID-19 antibody results in the POC qualitative test, which specificity was relatively All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted June 17, 2020. . https://doi.org/10.1101/2020.06.15.20132316 doi: medRxiv preprint low (94.6%). To determine the prevalence of COVID-19 in a given populations, antibody tests with high accuracy and consistent performance are needed not only in Iwate Prefecture but also in other areas in current Japan. This study has several limitations. First, it was a survey from a single medical institution with a relatively small blood samples. Moreover, the participants in this study were limited to healthcare workers in our hospital, so younger or older people were not enrolled in this study. Second, positive and negative control tests are significant for the full validation of COVID-19 antibodies and the assessment of non-specific binding. In this study, attempts to use the positive or negative control test have presented difficulties because of no identified infected cases and the stay-at-home order. Third, there is still a problem in reliability of antibody tests for COVID-19 and development of accurate tests should be needed. However, they are essential as an epidemiologic tool even in a given population with low prevalence to track progression towards herd immunity for a long time In conclusion, the positive rate of SARS-CoV-2 antibodies in healthcare workers of our hospital was 0%. Our results suggest the presence of no COVID-19 cases in Iwate Prefecture and the necessity of the antibody tests with high specificity in the areas with very low prevalence. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. This study did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors. The authors declare that they have no competing interests. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted June 17, 2020. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted June 17, 2020. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted June 17, 2020. . https://doi.org/10.1101/2020.06.15.20132316 doi: medRxiv preprint A new coronavirus associated with human respiratory disease in China Overlapping and discrete aspects of the pathology and pathogenesis of the emerging human pathogenic coronaviruses SARS-CoV, MERS-CoV, and 2019-nCoV World Health Organization declares global emergency: A review of the 2019 novel coronavirus (COVID-19) Ministry of Health and Labor of Japan Information on the Coronavirus (COVID-19) -Iwate Prefecture Antibody Testing For Covid-19 US Food and Drug Administration The authors gratefully acknowledge clinical laboratory technologists in Iwate Prefectural Central Hospital for their technical work with blood sampling and measurement.All rights reserved. No reuse allowed without permission.(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint this version posted June 17, 2020. . https://doi.org/10.1101/2020.06.15.20132316 doi: medRxiv preprint All rights reserved. No reuse allowed without permission.(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. All rights reserved. No reuse allowed without permission.(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint this version posted June 17, 2020. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint this version posted June 17, 2020. . https://doi.org/10.1101/2020.06.15.20132316 doi: medRxiv preprint