The goal of this observational cohort study is to evaluate the association between gut microbiota composition, dietary patterns, lifestyle-related factors, and neurodevelopmental outcomes, as well as susceptibility to SARS-CoV-2 infection, in a predominantly school-aged population and their adult contacts (family and teachers).

This study aims to answer the following main questions:

• Are specific gut microbiota profiles and dietary patterns associated with cognitive and behavioral development in non-clinical children and adolescents?
• Can baseline gut microbiota and lifestyle-related factors be associated with susceptibility to SARS-CoV-2 infection during the pandemic period?

The cohort includes more than 900 participants recruited between November and December 2020 in Valencia, Spain, including children and adolescents (approximately 3-19 years of age), as well as their family members and teachers. The cohort is structured into two predefined subcohorts. One subcohort includes children and adolescents and focuses on neurodevelopmental outcomes. The second subcohort includes both pediatric and adult participants and is used to evaluate gut microbiota-related factors in relation to SARS-CoV-2 infection.

Study assessments include stool sample collection for gut microbiota analysis, dietary assessment using validated food frequency questionnaires, and collection of sociodemographic, clinical, anthropometric, lifestyle, and health-related information through standardized questionnaires. Cognitive and behavioral outcomes in children and adolescents are assessed using validated instruments.

The study includes an initial cross-sectional assessment followed by a longitudinal follow-up over a 17-month period. During follow-up, stool samples were collected from participants who became infected with SARS-CoV-2 at different stages of the infection. At the end of the follow-up period, biological samples and study assessments were repeated when available.

The results of this study are expected to contribute to the identification of microbial, dietary, and lifestyle-related biomarkers associated with neurodevelopment and susceptibility to infectious diseases, supporting the development of preventive and non-pharmacological public health strategies.