One in 3,000 Unaware of COVID-19 Infection... "Small Sample Limits Generalization" (Update)

Central Disease Control Headquarters Announces Antibody Survey Results
0 Positive Cases out of 1,555 in First Round, 1 Positive out of 1,440 in Second Round
"Sample Size Too Small to Infer Undiagnosed Confirmed Cases"

At Seongnim Baptist Church in Gwangju Buk-gu Gakhwa-dong, where a COVID-19 cluster infection occurred, church members are undergoing diagnostic tests ahead of the end of their self-quarantine.

[Asia Economy Reporter Choi Dae-yeol] According to an antibody survey conducted by health authorities on approximately 3,000 general citizens for the novel coronavirus infection (COVID-19), only one person tested positive. This survey was conducted to check whether antibodies formed after recovery from COVID-19 infection had developed, indicating that the number of undetected patients infected within the community is very low. However, authorities note that since the sample size is still small, there are limitations in explaining the overall situation in South Korea based solely on the data collected so far.

According to the antibody survey results announced by the Central Disease Control Headquarters on the 14th, the first survey conducted from late April to mid-June, targeting 1,555 cases, showed no positive antibody or neutralizing antibody responses. The first survey was conducted in 14 cities and provinces excluding Daegu, Sejong, and Daejeon.

The second survey, conducted from mid-June to mid-August, targeted 1,440 cases and showed one positive response. The second survey was conducted in 13 cities and provinces, including Daegu, Sejong, and Daejeon. The government conducts an annual National Health and Nutrition Examination Survey targeting 10,000 general citizens nationwide, and this year, the COVID-19 antibody item was newly included in the survey. Separately from the National Health and Nutrition Examination Survey, a previous survey conducted in May on 1,500 patients visiting medical institutions in the southwestern area of Seoul also showed one positive response.

Jung Eun-kyung, head of the Central Disease Control Headquarters (Director of the Korea Disease Control and Prevention Agency, left), and Jung Kyung-tae, head of the Vaccine Research Division, are answering reporters' questions related to antibody testing methods following the regular briefing on the domestic COVID-19 outbreak status and interim investigation results of confirmed cases held on the afternoon of the 14th at the Korea Disease Control and Prevention Agency in Cheongju, Chungbuk.

Antibody Survey Using Rapid Kits Has Lower Accuracy
Expanding Survey Scope to Estimate Undiagnosed Confirmed Cases

Depending on whether only the sample size from the second survey is used as the population or if the samples from both the first and second surveys are combined, the antibody prevalence rate is less than 0.1% in either case. It is approximately 0.03% or 0.07%, and health authorities stated that it is currently limited to estimate the total number of infected individuals in the country based on this. In Daegu, where a past outbreak occurred, a university survey targeting visitors to hospitals in Daegu and Gyeongsan showed a 7.6% antibody prevalence rate; however, the authorities explained that it is difficult to compare directly because the sample quality and quantity were different, and the diagnostic method used was a rapid test with limitations.

Looking at overseas cases, test results vary depending on the testing method used. In Spain, where rapid kits were used nationwide, some areas showed rates as high as 10%, while others showed nearly 2%. In New York City, USA, where the outbreak was severe, antibody prevalence was reported to be as high as 24.7%. Rapid kits have lower reliability as they can react to common coronaviruses as well. Our authorities applied both antibody tests (IgM and IgG) and neutralizing antibody tests that actually neutralize the virus for the survey.

At a briefing on the same day, Jung Eun-kyung, head of the Central Disease Control Headquarters, explained, "According to expert advice, the second survey results are limited in explaining the current epidemic situation as the specimen collection period was before mid-last month." She added, "Since the neutralizing antibody test detects antibodies with protective effects, the positive rate tends to be low, and experts believe that the positive rate is not high because widespread regional infections like those in the US and Europe have not occurred." She further noted, "With only about 1,500 to 3,000 specimens, there is a limitation in the sample size to detect positive rates or undiagnosed positive cases."

To improve testing effectiveness and monitor actual positive rate trends, the survey scope will be expanded by increasing the number of subjects in the National Health and Nutrition Examination Survey and conducting PCR tests on military recruits. Additional surveys are being prepared for about 3,300 general citizens and medical staff in the Daegu and Gyeongsan areas, as well as 10,000 military recruits. Furthermore, approximately 10,000 representative regional specimens will be secured to conduct the same survey.

This content was produced with the assistance of AI translation services.