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Multicenter Study
. 2024 Nov 11:12:e18384.
doi: 10.7717/peerj.18384. eCollection 2024.

Seroprevalence and silent infection rate during SARS-CoV-2 pandemic among children and adolescents in Western Pomerania: a multicenter, cross-sectional study-the COVIDKID study

Marcus Vollmer #  1 , Daniela Kuthning #  2 , Jana Gramenz  2 , Arevik Scholz  2 , Robin Michael  2 , Nico Wittmann  2   3 , Udo Gesser  4 , Christian Niesytto  5 , Antje Vogler  6 , Vanda Tuxhorn  7 , Ute Lenschow  8 , Anja Lange  2 , Kristina Linnemann  9 , Holger Lode  10 , Lars Kaderali  1 , Almut Meyer-Bahlburg  2   3
Affiliations
Multicenter Study

Seroprevalence and silent infection rate during SARS-CoV-2 pandemic among children and adolescents in Western Pomerania: a multicenter, cross-sectional study-the COVIDKID study

Marcus Vollmer et al. PeerJ. .

Abstract

Background: Limited data on SARS-CoV-2 seroprevalence in rural areas of northern Germany necessitate comprehensive cohort studies. We aimed to evaluate the seroprevalence, silent infection (SI) rates and risk factors for infections among children and adolescents in Western Pomerania from December 2020 to August 2022.

Methods: In this cross-sectional study, serum or plasma samples from children and adolescents (6 months to 17 years) were collected during routine blood draw. SARS-CoV-2 specific antibodies (S1 and nucleocapsid) and their neutralizing capacity were analyzed using commercially available enzyme-linked immunosorbent and neutralization assays. Socio-demographic data and information about SARS-CoV-2 infection or vaccination were obtained. Multivariable logistic regression was used to identify independent risk factors for SARS-CoV-2 infections and SI.

Results: A total of 1,131 blood samples were included into the study. Overall, SARS-CoV-2 seroprevalence was 25.1%, strongly influenced by the pandemic course, predominant virus variants, age and approval of vaccination. SI rate was 5.4% (95%-CI [3.7%-6.8%]) among unvaccinated and undiagnosed children over the entire study period with highest rates among adolescents. Main risk factor despite the time at risk for silent infections was an infected household member (Odds ratio = 9.88, 95%-CI [4.23-22.9], p < 0.001). Factors associated with overall infections (known and silent) also include the infection of a household member (Odds ratio = 17.8, 95%-CI [10.7-29.6], p < 0.001).

Conclusions: We believe that the introduction of governmental measures and systematic test strategies in schools strongly impacted on the SI rate, as we suspect that asymptomatic cases have already been identified, resulting in surprisingly low SI identified in our study.

Keywords: Covid-19; IgA-S1; IgG-S1; NCP-IgG; Pandemic; Pediatric; SARS-CoV-2; Serology; Seroprevalence; Silent infection.

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Conflict of interest statement

Almut Meyer-Bahlburg received funding for the project by the Ministry for Economics, Labour and Health Mecklenburg-Vorpommern. Lars Kaderali was a member of the Corona Expert Council advising the Federal Government of Germany.

Figures

Figure 1
Figure 1. Infection rates in children and adolescents in the study region of Western Pomerania, Germany.
Regional incidences per 1,000 children for each age group printed as 7-day average, with single infections shown as dots. Dominating variants were calculated from variant PCR (change points were defined at 50% domination). Study periods of the COVIDKID study are defined at these change points. Start of vaccination campaigns for adults and children are indicated by green bars, mandatory wearing of masks is indicated in red. Red areas showing lockdown measures depending on restriction intensity and relaxations labeled at major events.
Figure 2
Figure 2. Anti-SARS-CoV-2 IgG response and seropositivity.
Anti-SARS-CoV-2-antibodies are evident in children and adolescents. (A) Anti-S1 IgG response and (B) seropositivity of all study participants at time of study inclusion, contingent upon self-disclosed SARS-CoV-2 vaccination and infection status. Vertical blue line indicates manufacturer’s recommended cut-off (ratio IgG-S1 ≥ 1.1). Seropositivity (green boxes in B) was inferred based on defined rules. Samples with missing information about infection and vaccination status were categorized as “unknown”.
Figure 3
Figure 3. Estimated rates of recovered or SARS-CoV-2-vaccinated children and seroprevalence.
Seroprevalences across age groups were estimated using LOESS. Dashed lines shows the official vaccination start in the study region depending on the respective age group.
Figure 4
Figure 4. Anti-SARS-CoV-2-antibodies in time course.
Individual anti-S1 antibodies of recruited participants related to their anamnestic infection and vaccination status. Dashed lines indicating vaccination approvals in respective age groups, red areas indicating infection control measures in Western Pomerania, depending on harshness of restrictions.
Figure 5
Figure 5. Sensitivity of serological tests before and after emerging Omicron variants.
(A) Correlation of IgG-S1 ratio with other serological tests in relation to the time since self-reported infection in children and adolescents, (B) Sensitivity of serological tests in combination with the IgG-S1 ratio and the dominating variant at the time of infection. Horizontal and vertical lines indicate the manufacturer’s cut-offs for the respective tests.
See this image and copyright information in PMC

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