








key: cord-338333-yvm3d6xy
authors: Tu, Danna; Shu, Junhua; Wu, Xiaoli; Li, Heng; Xia, Zhi; Zhang, Yanfang; Fang, Yaohui; Shen, Shu; Guan, Wuxiang; Wang, Hualin; Huang, Zhaoxuan; Wang, Guirong; Zhou, Xiaoqin; Deng, Fei
title: Immunological detection of serum antibodies in pediatric medical workers exposed to varying levels of SARS-CoV-2
date: 2020-07-25
journal: J Infect
DOI: 10.1016/j.jinf.2020.07.023
sha: 
doc_id: 338333
cord_uid: yvm3d6xy

• Pediatric healthcare workers are at risk for SARS-CoV-2 transmission from children and aerosols increase SARS-CoV-2 infection rate. • ELISA and dual-target fluorescence accurately detect SARS-CoV-2 antibodies indicated that antibody detection should be considered as an auxiliary diagnosis of COVID-19. • Antibody positive subjects tested negative for SARS-CoV-2 neutralizing antibodies and SARS-CoV-2 antibodies diminish to near undetectable levels within two months.

Highlights Pediatric healthcare workers are at risk for SARS-CoV-2 transmission from children and aerosols increase SARS-CoV-2 infection rate.

ELISA and dual-target fluorescence accurately detect SARS-CoV-2 antibodies indicated that antibody detection should be considered as an auxiliary diagnosis of COVID-19.

Antibody positive subjects tested negative for SARS-CoV-2 neutralizing antibodies and SARS-CoV-2 antibodies diminish to near undetectable levels within two months.

Dear Editor:

Since the initial reports of COVID-19 disease outbreak in Wuhan, China, it has continued to spread rapidly with cases identified in virtually all countries, worldwide [1] . The population is generally susceptible to SARS-CoV-2, including children and pregnant women, and medical staffs are a high-risk population for this disease. In this journal, Chen et al. have reported the high SARS-CoV-2 antibody prevalence among healthcare workers exposed to COVID-19 patients [2] .

Here we would like to share our finding about the serum antibodies analyzed in a special group of pediatric medical workers exposed to varying levels of SARS-CoV-2 after Wuhan severe epidemic of COVID-19.

A preliminary study suggests children can be infected with SARS-CoV-2 like adults but are less likely to be symptomatic or develop severe symptoms [3, 4] . The asymptomatic or mildly symptomatic children might transmit the disease [5]. Therefore they are tested for SARS-CoV-2 less often than adults, leading to an underestimate of the true numbers of children infected [6] .

Laboratory tests play a pivotal role in the diagnosis and management of COVID-19; the current gold standard being real-time reverse transcription polymerase chain reaction (rRT-PCR) on respiratory tract specimens [7] . The measurement of specific COVID-19 antibodies (both IgG and IgM) should serve as an additional, non-invasive tool for disease detection and management, especially in patients who present late, with a low viral load. Due to the high infection rate of medical workers and the uncertainty of child-to-person transmission, we chose a special group of pediatric medical workers as the research subjects to investigate their infection status with SARS-CoV-2 and analyze possible causes. This study also helps clarify the potential of different immunological techniques for antibody detection as an auxiliary diagnosis of COVID-19.

On March 19-20, 2020, pediatric medical workers (n = 325) in one hospital but not the designated hospital for COVID-19 in Wuhan were recruited. They were divided into three groups depends on their level of contact with confirmed and/or suspected COVID-19 cases during the outbreak: i. close contact group (contact with confirmed and/or suspected cases of COVID-19), ii.

non-close contact group (contact only with non-COVID-19 patients), and iii. non-contact group (no contact with any patients). Three different immunological detection methods were used to measure SARS-CoV-2 serum antibodies: colloidal gold-based detection, enzyme-linked immunosorbent assay (ELISA), and dual-target immuno-fluorescence assay (DTFA) (details in the Supplementary methods). The overall positive rate for SARS-CoV-2 IgG and IgM antibodies in the pediatric medical workers was 43.08 and 5.85%, respectively. For the close contact, non-close contact, and non-contact groups, respectively, the DTFA positive rates for IgG were 41.36, 14.68, and 12.50% (P < 0.05), and the ELISA positive rates for IgG were 34.55, 10.91, and 4.17% (P < 0.05) and 8.38, 0.91, and 0% for IgM (P < 0.05). Colloidal gold detection results were negative for IgG and only two participants tested positive for IgM, both in the close contact group.

It suggests the colloidal gold detection kit used in this research is not sensitive enough to be useful in accurate antibody detection, whereas the DTFA and ELISA positive rate performed similarly.

We further conducted a multivariate logistic regression analysis using antibody results as the independent variables to investigative the relationship of positive serum antibody results, with the performance of aerosol procedures, exposure levels to COVID-19 cases, clinical symptoms (including fever, cough, headache, stuffy nose, runny nose, sneezing, pharyngalgia, diarrhea, fatigue, etc.), chest CT imaging changes, and age of participant ( Table 2 ). The results showed that Although we cannot clearly track antibody kinetics for asymptomatic infections, we can observe that the majority of participants with positive IgG antibodies had a significant decline in antibody levels after one month. That means the SARS-CoV-2 antibodies diminish to near undetectable levels within two months.

This research revealed that pediatric medical workers are a high-risk group for infection by SARS-CoV-2, and the higher the exposure levels to COVID-19 patients and aerosol production, the greater chance of being infected. Meanwhile, we found that pediatric workers had lower levels of IgG antibodies than patients with COVID-19 [2] . Children-to-person transmission is almost inevitable, but pediatric medical workers often have no or only mild clinical symptoms and also cannot produce enough antibodies to neutralize the virus. The antibody protection that healthcare workers obtained after infection by SARS-CoV-2 in this study, could not be maintained for a long time and no NAbs were detected to provide them with sufficient protection.

None. Table 1 Test results of serum antibodies in pediatric medical workers exposed to different levels of SARS-CoV-2 

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