What is the correlation between specific COVID-19 clinical characteristics and anti-SARS-CoV-2 antibody titers?

By Tarun Sai LomteNov 3 2022Reviewed by Aimee Molineux

In a recent study posted to Research Square* preprint server, researchers investigated the associations between clinical characteristics of coronavirus disease 2019 (COVID-19) and immunoglobulin G (IgG) antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

*Important notice: Research Square publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Background

To date, more than 628 million COVID-19 cases have been recorded, with more than 6.5 million deaths worldwide. A COVID-19 outbreak occurred in one of the largest schools in Jerusalem, Israel, in late May 2020, affecting nearly 200 students and staff members. This was one of the most extensive outbreaks in a single academic institution prompting real-time polymerase chain reaction (RT-PCR) testing for almost everyone in the school community.

Multiple studies have demonstrated that anti-SARS-CoV-2 IgG and IgM antibodies could be detected in sera of adult individuals within 20 days post-symptom onset. Further, reports suggest that these antibodies last for at least seven months in adults. However, there is limited information on how long the anti-SARS-CoV-2 antibodies persist in younger populations after symptomatic or asymptomatic COVID-19.

The study and findings

In the current study, researchers evaluated the correlations between anti-SARS-CoV-2 IgG and clinical features of COVID-19 in a heterogeneous population comprising students, staff, and their household members. Blood samples were collected from the students and staff members of Hebrew Gymnasium (high school) in December 2020. Moreover, samples were obtained from their household members.

The participants provided clinical data, demographic information, and RT-PCR result data through online questionnaires. Samples were excluded from analysis if clinical data were lacking. Likewise, participants were excluded if they tested SARS-CoV-2-positive before or after June 2020. Samples were tested for anti-SARS-CoV-2 IgG antibodies by enzyme-linked immunosorbent assay (ELISA) using the DiaSorin’s LIAISON SARS-CoV-2 kit.

There were 532 participants with available data. Of these, 395 were students and their household members, and 137 were staff and their household members. Most participants were female, and the average age was 31 years. The proportion of infected household members was significantly higher among students’ households than among households of staff.

Myalgia and fever were less common in students during acute COVID-19 than in other study groups. Other acute and residual symptoms were comparable among participants. Anti-SARS-CoV-2 IgG antibodies were detected in 120 (out of 150) PCR-positive subjects seven months after testing SARS-CoV-2-positive, implying 80% sensitivity of the serologic test.

PCR-positive but seronegative individuals had fewer PCR-positive and COVID-19-symptomatic household members than PCR-positive and seropositive individuals. Sixteen participants reported PCR-negative status but were found seropositive. These individuals showed fewer symptoms during acute illness and had fewer PCR-positive and symptomatic household members.

Mean IgG antibody levels of PCR-positive and seropositive individuals were significantly higher than seropositive but PCR-negative participants. IgG levels were significantly higher in seropositive students than in other seropositive individuals. The IgG titers were not significantly different between symptomatic and asymptomatic participants.

A multivariable linear regression model showed the correlation of some symptoms (fever, rash, and weakness) with higher IgG titers during acute illness. COVID-19-related hospitalization, chronic immune suppression, and diabetes were associated with elevated IgG titers. There was an inverse relationship between age and IgG titers.

Conclusions

In summary, the findings indicated 80% sensitivity of serologic testing seven months after infection compared to 100% sensitivity when tested 20 days or later post-infection. Participants’ age was inversely related to IgG titers. Specifically, mean IgG titers of children and adolescents were 150% higher than those of adults aged 18 or above. Recall bias was likely given the study’s retrospective and self-reporting design.

*Important notice: Research Square publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.