# SARS-CoV-2 Infection Among Children in Rondônia, Western Brazilian Amazon: SARS-CoV-2 Among Children in Rondônia

## TL;DR

This study examines SARS-CoV-2 infection in children in Rondônia, Brazil, finding high positivity rates in unvaccinated and ineligible age groups, with Delta and Omicron variants being prevalent.

## Contribution

The study provides insights into SARS-CoV-2 infection patterns in children in the Western Brazilian Amazon, including variant prevalence and vaccination status.

## Key findings

- Children aged 10–14 years had the highest SARS-CoV-2 positivity rate.
- Delta variant (AY.99.2) was the most prevalent, followed by Omicron (BA.1.1) and Gamma (P.1).
- Most cases were in unvaccinated or ineligible children, with mild symptoms and a median viral load of 7.26 log10 copies/mL.

## Abstract

We analyzed 364 children symptomatic or asymptomatic for respiratory symptoms, aged 0.1 month–17 years, selected from primary healthcare units of different municipalities of Rondônia from June 2021 to September 2022. Data were collected from medical and electronic records for epidemiological characterization. The positive cohort (n = 96) was quantified using a real-time (RT) qPCR and sequenced by next-generation sequencing. Whole-genome sequences were obtained, SARS-CoV-2 strains were classified using the Pango system, and the maximum likelihood method was used for phylogenetic analyses. Among the patients, 59.34% (216/364) were male and 40.66% (148/364) were female. Children aged 10–14 years showed the highest rate of SARS-CoV-2 positivity. At the time of collection, 54.12% (197/364) of the patients were not age-eligible for immunization against COVID-19. The unvaccinated group accounted for 34.07% (124/364), with the highest proportion in the age groups of 5–9 and 10–14 years. Most patients exhibited mild symptoms. Seventy-nine high-quality genomes were obtained: Delta variant of concern (VOC) was the most prevalent (most abundant strain: AY.99.2), Omicron VOC was reported in 26 individuals (most frequent subvariant: BA.1.1), and Gamma VOC with 22 cases (12 cases of P.1 strain). The viral load showed a median of 7.26 log10 copies/mL, with a mean symptom duration of 4 days. Most of the cases were from children who were unvaccinated and age-ineligible for immunization and were associated with Delta and Omicron VOCs with an increase in subvariants during the study period.