SARS-CoV-2 infection- induced seroprevalence among children and associated risk factors during pre- and omicron-dominant wave, from January 2021 through November 2022, Thailand: Longitudinal study

Abstract

Background Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection can be asymptomatic in young children. Therefore, the true rate of infection is likely underestimated. Few data are available on the rate of infections in young children, and studies on the SARS-CoV-2 seroprevalence among children during omicron wave are limited. Our study aims to assess the SARS-CoV-2 infection-induced seroprevalence among children and estimated the associated risk factors for seropositivity. Methods A longitudinal serological survey was conducted from January 2021 through November 2022. Samples were tested for anti-nucleocapsid (N) IgG, anti-receptor binding domain (RBD) IgG using a chemiluminescent microparticle immunoassay (CMIA) and detected anti-RBD Immunoglobulin (Ig) using an electrochemiluminescence immunoassay (ECLIA). The vaccination and SARS-CoV-2 infection history were collected. Results A total of 452 serum samples were obtained from 249 children aged 5–7 years old who were annually followed-up in the longitudinal serological survey. Of these, 191 participants provided samples at two serial time points, including during the pre-and omicron dominant wave. Overall, seroprevalence induced by SARS-CoV-2 infection was increased from 9.1% (95%CI: 0.6-12.6%) during the pre-omicron wave to 49.7% (95%CI: 35.9-66.8%) during the omicron wave. Amongst seropositive individuals, the infection-induced seroprevalence was lower in vaccinated participants than those with no vaccination (40.4% vs. 57.4%; risk ratio, 0.71; 95%CI: 0.52–0.95). Nevertheless, the ratio of seropositive cases per recalled infection was 1.56 during the omicron dominant wave. In addition, overall seroprevalence induced by infection, vaccination and hybrid immunity was 76.6% (151/197; 95%CI: 54.6-97.9%) between January and November 2022. Conclusions our study reports an increase in infection-induced seroprevalence among children during the omicron wave. These findings highlight that estimating seroprevalence is crucial to monitor SARS-CoV-2 exposure, particularly in asymptomatic infection, and help to optimize public health policies and determine the effect of immunization in the pediatric population.

Safety and effectiveness of vaccines against COVID-19 in children aged 5–11 years: a systematic review and meta-analysis

“… 26 , 27 Studies were primarily done in high-income countries (eg, the USA, Canada, and Israel), and assessed a complete primary schedule of BNT162b2 vaccine (n=46 [90%]). Three (6%) studies only assessed the effect of a single dose of either BNT162b2 or mRNA-1273, 28 , 29 , 30 and nine (18%) studies assessed the effect of a monovalent 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 or bivalent (BNT162b2 bivalent [against original strain or omicron BA.4 or BA.5]) 39 booster vaccination ( appendix 1 pp 26–33 ). Participants' age was in line with the authorised age group (ie, 5–11 years for studies on BNT162b2 or BNT162b2 bivalent and 6–11 years for studies on mRNA-1273; appendix 1 pp 26–33 ).…”

“…As recommended in the ROBINS-I guidance, outcomes rated with a critical risk of bias were not included in data synthesis. 15 Excluded outcomes were SARS-CoV-2 infections in one study, 36 COVID-19-related hospitalisation in three studies, 27 , 40 , 41 ICU admissions in two studies, 27 , 41 deaths reported in one study, 41 and myocarditis in one study ( appendix 1 pp 34–36; appendix 2 ). 35 …”

Seroprevalence of severe acute respiratory syndrome coronavirus 2 N antibodies between December 2021 and march 2023 in Japan

“…The seroprevalence of antibodies against the N protein in Japan was reported to be 3.5% in February to March 2022 [1] and cumulative confirmed cases as of May 2023 exceeded 33.8 million (28.2% of the Japanese population). Unlike other countries where seroprevalence rates exceeded 50% [3, 4, 6–10], most of the Japanese population had not been infected at that time, suggesting the possibility of future SARS-CoV-2 epidemics in Japan.…”

“…The threat of SARS-CoV-2 is subsiding as most people have acquired sufficient antibodies through vaccination and/or infection to prevent severe COVID-19; more than 80% of the populations of major industrialized countries have antibodies against the S protein induced by vaccination and/or infection [1–5]. In contrast, the seroprevalence of antibodies against the N protein elicited by SARS-CoV-2 infection ranged from 44.4% to 80.2% in the United States, England, Spain, Slovenia, Switzerland, and Thailand between March and November 2022 after the emergence of the omicron variants [3, 4, 6–10]. The positive rate was higher among younger individuals than among the elderly [8].…”

Clinical manifestations and outcomes of coronavirus disease 2019 among pediatric liver transplant recipients in the delta and omicron variant pandemic: A retrospective study

“…[14] The increased prevalence of the disease after the omicron variant pandemic was also demonstrated in healthy Thai children. [15] While the patients infected with the omicron variant may be younger than the delta variant, [14] our patients’ ages were comparable in both periods of the pandemic.…”