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Seroprevalence of SARS-CoV-2 and risk factors for infection among children in Uganda: a serial cross-sectional study

Background: Understanding the burden of COVID-19 infection in pediatric populations is crucial for guiding public health interventions and policies. However, there are few age-stratified data available on COVID-19 infection in children, including in Uganda. This study describes the seroprevalence of SARS-CoV-2 and risk factors for infection among children across Uganda at two survey timepoints. In addition, data are reported on COVID-19 related knowledge, attitudes, and practices from Ugandan households, including adult vaccination status. Methods: Baseline cross-sectional community surveys were carried out in 12 communities from April to May 2021 (post-Alpha wave), followed by surveys in 32 communities from November 2021 to March 2022 during the Omicron wave. A household questionnaire was administered and blood samples were collected to assay for presence of malaria parasites by microscopy and SARS-CoV-2 seropositivity using a Luminex assay. Seroprevalence was estimated at the survey and community level. Mixed-effects logistic regression models measured associations between individual and household-level factors with SARS-CoV-2 seropositivity among children, adjusting for household clustering. Results: More households reported disruptions in daily life at baseline compared to follow-up, though economic impacts lingered. By the follow-up survey, 52.7% of eligible adults had received at least one COVID-19 vaccine dose. Overall adjusted seroprevalence in children was higher at follow-up compared to baseline (71.6% versus 19.2%, p < 0.001). Seroprevalence in children ranged across communities from 6-37% in the baseline survey and 50-90% in the follow-up survey. At baseline, children from the poorest households were more likely to be infected. Increasing age remained the only consistent risk factor for SARS-CoV-2 seroconversion at both timepoints. Conclusions: Results indicate that a larger number of children were infected during the Delta and Omicron waves of COVID-19 compared to the Alpha wave. This study is the largest seroprevalence survey in children in Uganda, providing evidence that most children were infected with SARS-CoV-2 before the vaccine was widely available to pediatric populations. Pediatric infections were vastly underreported by case counts, highlighting the importance of seroprevalence surveys in assessing disease burden when testing and reporting rates are limited and many cases are mild or asymptomatic.