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Background: Whether acute respiratory illnesses (ARIs), often associated with virus detection, are associated with lower risk for subsequent ARI remains unclear. We assessed the association between symptomatic ARI and subsequent ARI in young children.Methods: In a prospective cohort of Peruvian children <3 years, we examined the impact of index ARI on subsequent ARI risk. Index ARI were matched with ≤3 asymptomatic observations and followed over 28 days. We compared risk of subsequent ARI between groups using conditional logistic regression adjusting for several covariates, accounting for repeat observations from individual children.Results: Among 983 index ARI, 339 (34%) had an ARI event during follow-up, compared with 876/2826 (31%) matched asymptomatic observations. We found no significant association of index ARI and subsequent ARI risk during follow-up overall (adjusted odds ratio [aOR], 1.10; 95% confidence interval [CI], .98-1.23) or when limited to index ARI with respiratory viruses detected (aOR, 1.03; 95% CI, .86-1.24). Similarly, when the outcome was limited to ARI in which viruses were detected, no significant association was seen (aOR, 1.05; 95% CI, .87-1.27).Conclusions: ARIs were not associated with short-term protection against subsequent ARI in these children. Additional longitudinal studies are needed to understand drivers of recurrent ARI in young children. [ABSTRACT FROM AUTHOR]

Objectives: We examined the association of nasopharyngeal (NP) pneumococcal co-colonization (>1 pneumococcal serotype) and pneumococcal density in young Peruvian children enrolled in a prospective cohort study., Methods: NP swabs collected monthly from children aged <3 years during both asymptomatic and acute respiratory illness (ARI) periods underwent culture-enriched microarray for pneumococcal detection and serotyping and lytA polymerase chain reaction for density assessment. We examined the serotypes commonly associated with co-colonization and the distribution of densities by co-colonization, age, current ARI, and other covariates. The association of co-colonization and pneumococcal density was assessed using a multivariable mixed-effects linear regression model, accounting for repeated measures and relevant covariates., Results: A total of 27 children contributed 575 monthly NP samples. Pneumococcus was detected in 302 of 575 (53%) samples, and co-colonization was detected in 61 of these 302 (20%). The total densities were higher during ARI than non-ARI periods and lowest among the youngest children, increasing with age. In the multivariable analysis, there was no significant association between pneumococcal density and co-colonization (coefficient estimate 0.22, 95% confidence interval 0.11-0.55; reference: single-serotype detections). Serotypes 23B and 19F were detected significantly more frequently as single isolates., Conclusion: Pneumococcal co-colonization was common and not associated with increased pneumococcal density. Differential propensity for co-colonization was observed among individual serotypes., Competing Interests: Declarations of Competing Interest L. M. H. has received grant support from Pfizer for unrelated work. K. M. E. reports grant funding from the National Institutes of Health and Centers for Disease Control and Prevention; has served as a consultant to Bionet and IBM; and has served as a member of Data Safety and Monitoring Boards for Sanofi, X-4 Pharma, Seqirus, Moderna, Pfizer, Merck, and Roche. C. F. L. is a member of the World Health Organization COVID-19 vaccine effectiveness working group and reports grant funding from CureVac AG, PATH, and HilleVax from work not related to the current work. C. G. G. has served as a consultant to Pfizer, Merck, and Sanofi-Pasteur for unrelated work and received research support from Sanofi-Pasteur. All other authors report no potential conflicts of interest., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)