Contact with young children is a major risk factor for pneumococcal colonization in older adults

Background Important questions remain about the sources of transmission of pneumococcus to older adults in the community. This is a critical question for understanding the potential indirect effects of using pneumococcal conjugate vaccines (PCVs) in children and older adults. For non-institutionalized individuals, the most likely source of adult-to-adult transmission is in the household. The goal of this study was to characterize the dynamics and risk factors for acquisition of pneumococcus in older adults. Methods We designed a longitudinal study to sample adults >60 years of age living in the same household (New Haven, CT, USA), and without younger contacts residing in the household. Saliva samples and questionnaires regarding social behaviors and health status were obtained every 2 weeks for a period of 10 weeks. DNA extracted from culture-enriched saliva was tested using qPCR for pneumococcus genes piaB and lytA . Results Across two study seasons (November 2020-August 2021, November 2021-September 2022), 121 individuals from 61 households were followed for 6 study visits; 62 individuals were enrolled in both seasons. Overall, 52/1088 (4.8%) samples tested positive for pneumococcus based on piaB , with 27/121 (22.3%) individuals colonized on at least one time point. Several individuals were colonized at multiple timepoints including two individuals who were colonized throughout the 10-week sampling period; two others were colonized at 5 of 6 time points. In 5 instances, both members of the household were carriers in the same season, though not necessarily at the same time point. Pneumococcal carriage was substantially higher among individuals who had contact with children (10.0% vs 1.6%). Participants who reported recent contact with <5-year-olds and 5-9-year-olds had particularly elevated prevalence (13.8%; 14.1%, respectively). Conclusions Contact with young children was the most important factor that influenced pneumococcal acquisition rates. While there were several instances where both adult household members were colonized at the same time or at sequential visits, these individuals also both typically had contact with children. ### Competing Interest Statement ALW has received consulting and/or advisory board fees from Pfizer, Merck, Diasorin, PPS Health, Primary Health, Co-Diagnostics, and Global Diagnostic Systems for work unrelated to this project, and is Principal Investigator on research grants from Pfizer, Merck, NIH RADx UP and SalivaDirect, Inc. to Yale University and from NIH RADx, Balvi.io and Shield T3 to SalivaDirect, Inc.. DMW has received consulting fees from Pfizer, Merck, GSK, and Matrivax for work unrelated to this project and is Principal Investigator on research grants and contracts with Pfizer and Merck to Yale University. ### Funding Statement This study was conducted as a collaboration between Yale School of Public Health and Pfizer. Yale School of Public Health is the study sponsor. The study protocol was designed by the Yale researchers in consultation with Pfizer. The decision to publish was made by the Yale researchers in consultation with Pfizer; all authors agree with the decision to publish and with the results of the study. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study was approved by the Institutional Review Board at Yale School of Medicine (Protocol ID #2000026100). Demographic data and samples were collected after the study participant had acknowledged that they had understood the study protocol and provided digitally signed-informed consent, collected in the Research Electronic Data Capture (REDCap) electronic data capture tools hosted at Yale University. All participant information and samples collected were assigned anonymized study identifiers. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors