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Background and Objective: Childcare attendance is a common risk factor for acute respiratory illness (ARI) in young children. Our goal was to better understand the specific respiratory viruses that predominate in childcare, which may support the development of tailored illness prevention and intervention strategies in childcare settings., Methods: Using data from a prospective household cohort of ARI surveillance, we assessed specimen from 1418 ARIs reported by 359 childcare-aged children over 6 study seasons (2012/2013 through 2017/2018). Respiratory swabs were tested by polymerase chain reaction for 9 respiratory viruses. A mixed-effect logistic regression model was used to compare odds of various viral detection outcomes. The Shannon's Diversity index was used to compare the richness (ie, number of species) and diversity (ie, relative species abundance) associated with respiratory viruses detected in both groups., Results: At least 1 virus was detected in 75.5% of childcare-associated ARIs and in 80.1% of homecare ARIs. Compared with illnesses among homecare children, childcare illnesses were associated with significantly higher odds of detected adenovirus (odds ratio = 1.86, 95% confidence interval = 1.05-3.28) and human metapneumovirus (odds ratio = 1.76, 95% confidence interval = 1.03-3.0). The pool of viruses associated with childcare ARI was found to be significantly richer and more diverse than that of viruses associated with homecare ARI ( P < 0.0001)., Conclusions: Children attending childcare experience a higher risk of adenovirus and human metapneumovirus infection and are regularly exposed to a rich and diverse pool of respiratory viruses in childcare environments. Our results underscore the necessity of thorough and multifaceted viral prevention strategies in childcare settings., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

While influenza virus diversity and antigenic drift have been well characterized on a global scale, the factors that influence the virus’ rapid evolution within and between human hosts are less clear. Given the modest effectiveness of seasonal vaccination, vaccine-induced antibody responses could serve as a potent selective pressure for novel influenza variants at the individual or community level. We used next generation sequencing of patient-derived viruses from a randomized, placebo-controlled trial of vaccine efficacy to characterize the diversity of influenza A virus and to define the impact of vaccine-induced immunity on within-host populations. Importantly, this study design allowed us to isolate the impact of vaccination while still studying natural infection. We used pre-season hemagglutination inhibition and neuraminidase inhibition titers to quantify vaccine-induced immunity directly and to assess its impact on intrahost populations. We identified 166 cases of H3N2 influenza over 3 seasons and 5119 person-years. We obtained whole genome sequence data for 119 samples and used a stringent and empirically validated analysis pipeline to identify intrahost single nucleotide variants at ≥1% frequency. Phylogenetic analysis of consensus hemagglutinin and neuraminidase sequences showed no stratification by pre-season HAI and NAI titer, respectively. In our study population, we found that the vast majority of intrahost single nucleotide variants were rare and that very few were found in more than one individual. Most samples had fewer than 15 single nucleotide variants across the entire genome, and the level of diversity did not significantly vary with day of sampling, vaccination status, or pre-season antibody titer. Contrary to what has been suggested in experimental systems, our data indicate that seasonal influenza vaccination has little impact on intrahost diversity in natural infection and that vaccine-induced immunity may be only a minor contributor to antigenic drift at local scales. [ABSTRACT FROM AUTHOR]

Background Out-of-home child care (CC) is a risk factor for viral acute respiratory infection (ARI) in young children. Little is known, however, about differences in frequencies of viral infection between CC children and those cared for exclusively at home. Methods Using surveillance data from the HIVE household cohort in southeast Michigan from 2014–2018 (4 seasons), we analyzed 1022 illness cases from 354 children aged 0–6 years. Age groups were dichotomized as infants (aged <2 years) and toddlers/preschoolers (aged 2–6 years). Households were prospectively enrolled and nasal respiratory swabs were collected from children upon report of acute illness symptoms. We used real-time RT–PCR to test for 18 respiratory viruses. Results We detected at least one virus in 855 illness cases (83% of all illnesses reported). Age at first illness onset in all four seasons was significantly younger among CC children than homecare children (P < 0.001) across all 4 years (average difference = 1.25 years). CC children <2 years had slightly lower odds of viral detection during illness (OR = 0.89, 95% CI [0.49, 1.61]) but higher odds at ages 2–6y (1.07 [0.65, 1.76]); neither was statistically significant. Neither CC nor homecare children were significantly more or less at risk for any particular pathogen—expect for rhinovirus in the <2-year group, where odds of rhinovirus infection were 58% lower (OR = 0.42) in CC children compared with homecare counterparts (95% CI, 0.21–0.83). Conversely, CC attendees under 3 more frequently had influenza, RSV, hMPV, parainfluenza, and coronavirus; however, none of these associations were significant. Odds of coinfection (> 1 virus detected) were higher among CC children, but not significant (OR = 1.4 [0.63, 2.96] and 1.2 [0.77, 1.88] in <2 year and 2–6 year age groups, respectively). Among all children <7 year, the mean number of pathogens detected was not different between CC and homecare individuals (1.20 vs. 1.23, P = 0.16). Conclusion As expected, results indicated that CC attendees aged 0–6y experienced illness episodes earlier in life compared with homecare children. Our analysis also indicated that, compared with children cared for at home, CC children were less at risk for rhinovirus infection when young but could potentially be at higher risk for viruses of greater clinical concern. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]