key: cord-1030508-t97gg9qm
authors: Torres, Juan P.; Sauré, Denis; Basso, Leonardo J.; Zuñiga, Marcela; Cazor, Andre; O'Ryan, Miguel
title: SARS-COV-2 IgG positivity in vaccinated and non-vaccinated Chilean children: a national cross-sectional study in Schools
date: 2022-04-25
journal: Int J Infect Dis
DOI: 10.1016/j.ijid.2022.04.039
sha: 626a3be853832cc9f50916f00c6e1fda280cddbb
doc_id: 1030508
cord_uid: t97gg9qm

nan

inactivated Sinovac vaccine. We previously reported a national COVID-19 IgG seropositivity study in adults vaccinated with either vaccines demonstrating the utility of large cross-sectional immunologic surveys using lateral flow tests (LFT) (Sauré 2022) . We report here IgG seropositivity in vaccinated and non-vaccinated Chilean school-aged children, receiving the inactivated vaccine from Sinovac (CoronaVac) or the mRNA vaccine from Pfizer/BioNTech (BNT162b2) within one to twenty weeks before sample collection, or no vaccine. Data on IgG seropositivity among vaccinated children with inactivated as compared to mRNA vaccines is currently non-existent, and can provide important information for decision makers worldwide.

We performed SARS-CoV-2 IgG testing using the Onsite (CTK Biotech Inc, US) LFT. This was the same LFT used in adults (Sauré 2022) , with a reported sensitivity and specificity of 96.7% and 98.1% (CTK Biotech 2021). In conjunction with the Chilean Ministries of Education and Health, 24 schools located in the 3 most populated regions in Chile were invited to take part in the study.

Briefly, all parent/children pairs were invited to participate through a letter sent by school authorities. Accepting parents signed informed consent and children over 8 years of age an assent.

Children of every accepting parent were tested. Trained staff in each school obtained basic information from the parent/caregiver of the child participant including type of vaccine and vaccination dates, age, gender, country of origin, general medical history, previous Covid-19 IgG or PCR testing, home address and usual transportation method to school. A finger prick blood was obtained in the child as previously described (Sauré 2022) . Tests were read on site and results (positive, negative, or not conclusive) as well as surveillance data were instantly uploaded through a web interface to a database harbored at the Instituto Sistemas Complejos de Ingeniería, as in previous reports (Sauré 2022) . The study was approved by the Comité de Ética de Investigación en Seres Humanos (Universidad de Chile, Santiago, Chile).

As of December 24, 2021, a total of 2302 children have been included as described in Table 1 .

While most Sinovac recipients were 6-11 years old (920), Pfizer/BioNTech recipients were almost exclusively 12-18 years old (647). IgG positivity was significantly higher for Pfizer compared to Sinovac recipients for all study variables except comorbidities (Table 1) . For 670 children receiving the Pfizer/BioNTech vaccine seropositivity was 91.7% three to four weeks after the second dose, with figures above 90% by 20 weeks after full vaccination (Figure 1 ). For 1506 children receiving Sinovac, seropositivity was 91.8 % three to four weeks after the second dose, with a declining trend thereafter (Figure 1 ).

In school-aged Chilean children, SARS-CoV-2 IgG seropositivity surpassed 90% two weeks after administration of a second dose in the case of the inactivated vaccine (Sinovac), and up to 10 weeks in the case of the mRNA vaccine (Pfizer/BioNTech). Compared to the adult population (Sauré 2022 ), children showed a slightly weaker response to the mRNA vaccine and a slightly stronger response to the inactivated vaccine, in terms of the overall proportion of seropositive individuals in the short-term period after vaccination. Yet, as for the case of adults, the seropositivity for the inactivated vaccine declines over time, suggesting that a booster dose will most likely be required 

This study was supported by funds provided by the Ministerio de Salud, Gobierno de Chile. The Ministerio de Salud had no role in designing the study, provided the lateral flow tests used in the study, and funded filed work.

This study was approved by the Ethics Committee for Clinical Investigation in Humans, from the Faculty of Medicine, Universidad de Chile. 

COVID-19 Vaccines in Children and Adolescents

CTKBiotech.com. 2021. Instructions for users

A wake-up call: COVID-19 and its impact on children's health and wellbeing

Immunogenicity, and Efficacy of the BNT162b2 Covid-19 Vaccine in Adolescents

Safety, tolerability, and immunogenicity of an inactivated SARS-CoV-2 vaccine (CoronaVac) in healthy children and adolescents: a double-blind, randomised, controlled, phase 1/2 clinical trial

Dynamic IgG seropositivity after rollout of CoronaVac and BNT162b2 COVID-19 vaccines in Chile: a sentinel surveillance study

Evaluation of the BNT162b2 Covid-19 Vaccine in Children 5 to 11 Years of Age

Incidence Rates and Clinical Outcomes of SARS-CoV-2 Infection With the Omicron and Delta Variants in Children Younger Than 5 Years in the US

to 4 weeks after first dose (light blue-shaded region) or after second dose for recipients of Sinovac or Pfizer vaccines with no prior positive PCR result

*The data exclude participants with incomplete information (n=6), inconsistent vaccination status information (n=86), region other than those listed (n=1), and vaccinated with vaccines other than Sinovac or Pfizer (n=11)

previously obtained which resulted positive ***Includes 4 cases of Hypertension, 4 cases of Diabetes and one case of Cancer

All authors declare not to have any conflict of interest. This work was partially supported by a grant from ANID PIA AFB 180003 (Instituto Sistemas Complejos de Ingeniería, ISCI. Field work and LFTs were funded by Subsecretaría de Redes Asistenciales, Ministerio de Salud, Chile. We