Early Viral Clearance and Antibody Kinetics of COVID-19 Among Asymptomatic Carriers

Abstract

Asymptomatic carriers contribute to the spread of Coronavirus Disease 2019 (COVID-19), but their clinical characteristics, viral kinetics, and antibody responses remain unclear. A total of 56 COVID-19 patients without symptoms at admission and 19 age-matched symptomatic patients were enrolled. RNA of SARS-CoV-2 was tested using transcriptase quantitative PCR, and the total antibodies (Ab), IgG, IgA, and IgM against the SARS-CoV-2 were tested using Chemiluminescence Microparticle Immuno Assay. Among 56 patients without symptoms at admission, 33 cases displayed symptoms and 23 remained asymptomatic throughout the follow-up period. 43.8% of the asymptomatic carriers were children and none of the asymptomatic cases had recognizable changes in C-reactive protein or interleukin-6, except one 64-year-old patient. The initial threshold cycle value of nasopharyngeal SARS-CoV-2 in asymptomatic carriers was similar to that in pre-symptomatic and symptomatic patients, but the positive viral nucleic acid detection period of asymptomatic carriers (9.63 days) was shorter than pre-symptomatic patients (13.6 days). There were no obvious differences in the seropositive conversion rate of total Ab, IgG, and IgA among the three groups, though the rates of IgM varied largely. The average peak IgG and IgM COI of asymptomatic cases was 3.5 and 0.8, respectively, which is also lower than those in symptomatic patients with peaked IgG and IgM COI of 4.5 and 2.4 (p < 0.05). Young COVID-19 patients seem to be asymptomatic cases with early clearance of SARS-CoV-2 and low levels of IgM generation but high total Ab, IgG, and IgA. Our findings provide empirical information for viral clearance and antibody kinetics of asymptomatic COVID-19 patients.

Evaluation of the SARS-CoV-2 positivity ratio and upper respiratory tract viral load among asymptomatic individuals screened before hospitalization or surgery in Flanders, Belgium

“…Young COVID-19 patients are known to be mainly asymptomatic or pauci-symptomatic [ 7 , 31 ]. Children may act as hidden drivers of the pandemic, although schools were found not to be a high risk setting for transmission of SARS-CoV-2 during the first and second wave of infections and several studies found that school closures did not contribute to the control of the epidemic [ 32 , 33 ].…”

“…Real-time RT-PCR is considered the reference standard for SARS-CoV-2 detection with lower cycle threshold (Ct) values corresponding to higher viral RNA concentrations and higher infectiousness [ 2 ]. Some studies reported lower SARS-CoV-2 viral loads in the nasopharynx/oropharynx of asymptomatic patients (children and adults) with shorter viral shedding compared to symptomatic patients [ 3 – 7 ]. Other studies observed similar viral loads in respiratory tract samples from asymptomatic or pre-symptomatic persons compared to symptomatic patients and long-term virus shedding in asymptomatic patients [ 2 , 8 – 10 ].…”

Antibody Response against SARS-CoV-2 Infection: Implications for Diagnosis, Treatment and Vaccine Development

“…In another recent study on 38 samples from 13 COVID-19 patients with known date of symptom onset, 33% of patients seroconverted for IgG between 3rd and 7th day pso [17]. Although, in this regard, some studies didn't report any significant difference among different type of patients (asymptomatic, pre-symptomatic, and symptomatic) [10,12,18], another two analytic studies underlined a major proportion of early responders among hospitalized [6,19] and severe patients [20]. In particular Iyer et al [19] reported that the median time to seroconversion to SARS-CoV-2 RBD was, on average,4 days earlier for ospitalized patients compared with non-hospitalized patients, suggesting an association between antibody kinetics and disease severity.…”

“…Regarding the kinetics of antibody response, studies have generally observed an increase of both IgG and IgM during the first 3 weeks post-symptoms onset (pso); at 3-4 weeks pso almost all patients presented seroconversion while both antibodies types reach the peak [10]. After the third week, IgM begin to decrease, while IgG remain stable for longer time and sustained levels were detected until 6-7 months so far, even if a great variability was observed among patients [9,[12][13][14][15][16]. However, interestingly, some studies that focused on the analysis of patients' serum starting from first days pso, have reported that most SARS-CoV-2 infected patients mount an early antibody response.…”

“…In another recent study on 38 samples from 13 COVID-19 patients with known date of symptom onset, 33% of patients seroconverted for IgG between 3rd and 7th day pso [ 17 ]. Although, in this regard, some studies didn’t report any significant difference among different type of patients (asymptomatic, pre-symptomatic, and symptomatic) [ 10 , 12 , 18 ], another two analytic studies underlined a major proportion of early responders among hospitalized [ 6 , 19 ] and severe patients [ 20 ]. In particular Iyer et al.…”