SARS-CoV-2 can potentially cause nosocomial outbreaks. Although high secondary attack rates (SARs) among adult roommates have been reported, data on pediatric settings are limited. This study aimed to evaluate the SAR of symptomatic SARS-CoV-2 infections in shared rooms in a children’s hospital.
A retrospective chart review from January 1, 2023, to December 31, 2023, was conducted at the National Center for Child Health and Development, one of the largest tertiary children’s hospitals in Japan. According to hospital policy, nucleic acid amplification tests for SARS-CoV-2 were required for all hospitalized patients who developed new-onset fever or respiratory symptoms during the study period. If the test result was positive, confirmed cases with SARS-CoV-2 infection were immediately transferred to an isolation ward, and their remaining roommates were closely monitored for 5 days following the diagnosis of the index case. The SAR of symptomatic SARS-CoV-2 infections among roommates was calculated.
Eighteen patients were identified as index cases with whom a total of 53 roommates had contact. Among these exposed roommates, secondary symptomatic SARS-CoV-2 infections occurred in 2 shared rooms, and the SAR within 5 days after the exposure from the index case was 5.7% (3/53).
The SAR of symptomatic SARS-CoV-2 infections in the largest tertiary children’s hospital in Japan was not high in this study. Further studies are warranted to validate our findings and to establish effective isolation and surveillance strategies for SARS-CoV-2 in hospitalized children.
Introduction
Health care–associated viral infections in children can be transmitted from roommates, family members, and health care workers.1,2 To develop an effective strategy for controlling hospital-acquired viral infections, it is essential to investigate data on the transmission of these viruses in hospital settings.
Although strict infection control measures, including comprehensive screening and isolation, are important to prevent outbreaks, they can result in excessive testing, increased costs, a greater demand for human resources, delayed diagnosis and treatment of underlying diseases, and prolonged isolation from caregivers. It is therefore essential to pursue a sustainable, balanced, and effective infection control strategy.
In adults, high secondary attack rates (SARs) of 12.3%-23.3% for SARS-CoV-2 have been documented in shared hospital rooms.3,4 Given these high SARs, it has been postulated that the screening and isolation of roommates are essential if a patient develops COVID-19 in a shared room. However, the pediatric data on this subject are limited. Therefore, we conducted a retrospective study to evaluate the SAR of symptomatic SARS-CoV-2 infections among roommates in a children’s hospital who had contact with the index cases.
Methods
Study Environment
The National Center for Child Health and Development (NCCHD) is one of the largest tertiary children’s hospitals in Japan, with 490 beds and a total of 71 shared rooms available in the general pediatric ward. There are 4 beds in the shared rooms; the distance between each bed is greater than 2 meters. There is also an isolation ward for patients with COVID-19. Due to the repeated epidemics of SARS-CoV-2 and other respiratory pathogens, the health care workers were required to wear masks and eye guards, in addition to the standard precautions, when caring for the patients.5 In October 2023, the protocol for using eye guards was modified. Previously, universal eye protection was required at all times; however, the new protocol requires eye protection only during droplet-contact precautions. In addition, family members with a fever or any respiratory or gastrointestinal symptoms were not allowed to visit their children. Visitors were also required to wear masks at all times during hospital visits.
The study period was from January 1, 2023, to December 31, 2023 (Omicron variant, including XBB.1.5, XBB.1.16, EG.5, and others, epidemic period).6 According to the hospital policy for strict COVID-19 infection control, all hospitalized patients developing new-onset symptoms of fever, nasal discharge, sore throat, and cough were subject to SARS-CoV-2 nucleic acid amplification tests (NAATs) of FilmArray Respiratory Panel 2.1 (BioFire Diagnostics) or ID NOW COVID-19 assay (Abbott Laboratories) to determine whether the symptoms were caused by SARS-CoV-2 infection. Due to the hospital rule, FilmArray was preferentially used in inpatient setting owing to its broader diagnostic capabilities, whereas ID NOW was used in special circumstances, such as when FilmArray was unavailable. Once the patients were diagnosed with COVID-19 (index cases), they were immediately transferred to the dedicated COVID-19 isolation ward. In addition, the roommates of the index case were closely monitored in the same room for more than 5 days in preparation for subsequent cases of COVID-19. Routine NAATs for SARS-CoV-2 were not performed on asymptomatic roommates. However, NAATs were performed if they developed symptoms such as fever and respiratory symptoms during the observation period.
Data Collection
We retrospectively extracted confirmed pediatric cases aged younger than 15 years with SARS-CoV-2 by NAATs during hospitalization. To accurately estimate SARs following the index cases, we excluded the following: (1) cases without roommates, (2) difficult-to-identify index cases (multiple COVID-19 cases found in the same room simultaneously), (3) cases with a history of laboratory-confirmed SARS-CoV-2 infection within 90 days, and (4) cases with a secondary attack of COVID-19 from another patient in the same shared room. The remaining cases were thus defined as index cases. Subsequently, the roommates of the index cases were identified through an examination of the bed map records. These roommates were classified as “contacts” if they had shared the room with an index case for a period exceeding 12 hours, during which the index case was infectious (48 hours prior to onset of symptoms or later). The clinical information was collected from the electronic medical records: inpatients’ symptoms such as fever, nasal discharge, sore throat, and cough were the subjects to be documented in the nursing and medical records. Thus, we reviewed whether the roommates showed any new-onset symptoms within 5 days after the contact with the index and the symptomatic roommates were diagnosed with SARS-CoV-2 infection by NAATs. The SAR was defined as the number of roommates who developed symptomatic SARS-CoV-2 infections within 5 days of the last exposure to the index case, divided by the number of all exposed roommates. The median and IQRs of consecutive numbers were calculated using Microsoft Excel.
Ethical Considerations
Given the retrospective nature of this study and the use of data pertaining to SARS-CoV-2 from an electronic medical record, the requirement for informed consent was waived. The data collection was conducted with the opt-out methodology, following the ethical guidelines for human research in Japan. The study was approved by the NCCHD ethics committee (approval number: 2023–253).
Results
A total of 1329 hospitalized patients in the general wards underwent NAATs between January 1 and December 31, 2023. FilmArray Respiratory Panel 2.1 was used for 1309 patients (98.5%), whereas ID NOW COVID-19 assay was used for 20 patients (1.5%). Among them, 49 patients (3.7%) tested positive for SARS-CoV-2, and 18 patients were identified as index cases. The index cases had contact with 53 roommates (Figure 1).
Regarding the index cases (n = 18), 8 patients (44%) were found to be immunocompromised given a history of solid organ or hematopoietic cell transplantation, current chemotherapy treatment, or the use of immunosuppressive medications. Similarly, among the roommates (n = 53), 19 patients (36%) were immunocompromised (Table 1). The SAR of symptomatic SARS-CoV-2 infection among the roommates was 5.7% (3/53). The secondary attacks occurred in 2 rooms that were shared by multiple children. One index case was a 1-year-old, immunocompetent child who developed a symptomatic SARS-CoV-2 infection. Subsequently, 2 out of the 3 immunocompetent roommates, aged 6 months and 6 years, developed symptomatic SARS-CoV-2 infections (Supplemental Figure 1). Another index case was a 1-year-old female infant undergoing chemotherapy for a solid tumor who developed symptomatic SARS-CoV-2 infection. One of the 3 roommates, aged 2 years, who was also undergoing chemotherapy in preparation for hematopoietic cell transplantation, subsequently developed a symptomatic SARS-CoV-2 infection. No further transmission of SARS-CoV-2 was identified from the roommates exposed to symptomatic SARS-CoV-2 infections. None of the 18 index and 3 secondary-infected cases developed severe COVID-19 requiring high-flow oxygen supplementation, ventilator support, or other intensive care unit management.
Characteristics of COVID-19 Index Cases and the Roommates
| Characteristics | Index (N = 18) | Roommates (N = 53) |
|---|---|---|
| Female sex, n (%) | 7 (39) | 30 (57) |
| Median age, years (IQR) | 3.9 (1.7–7.9) | 5.3 (1.9–11.7) |
| Onset of illness, median hospital days (IQR)a | 17.5 (5–106.25) | |
| Median number of roommates (IQR) | 3 (3–3) | |
| Duration of sharing room with index, median hours (IQR) | 55 (33–67) | |
| Immunocompromised condition, n (%) | ||
| Solid organ transplantation | 3 (17) | 8 (15) |
| Hematopoietic cell transplantation | 0 (0) | 1 (1.9) |
| Chemotherapy | 3 (17) | 9 (17) |
| Other | 2 (11) | 1 (1.9) |
| Mechanical ventilation, n (%) | 3 (17) | 3 (5.7) |
| Characteristics | Index (N = 18) | Roommates (N = 53) |
|---|---|---|
| Female sex, n (%) | 7 (39) | 30 (57) |
| Median age, years (IQR) | 3.9 (1.7–7.9) | 5.3 (1.9–11.7) |
| Onset of illness, median hospital days (IQR)a | 17.5 (5–106.25) | |
| Median number of roommates (IQR) | 3 (3–3) | |
| Duration of sharing room with index, median hours (IQR) | 55 (33–67) | |
| Immunocompromised condition, n (%) | ||
| Solid organ transplantation | 3 (17) | 8 (15) |
| Hematopoietic cell transplantation | 0 (0) | 1 (1.9) |
| Chemotherapy | 3 (17) | 9 (17) |
| Other | 2 (11) | 1 (1.9) |
| Mechanical ventilation, n (%) | 3 (17) | 3 (5.7) |
Days of hospitalization in which index case developed SARS-CoV-2 infection.
Discussion
In the current study of the children’s hospital, the SAR of symptomatic SARS-CoV-2 infections among the remaining roommates following index cases was 5.7% (3/53) when the isolation of index cases was conducted promptly.
Although the data regarding the SAR among hospitalized children are limited, it has been reported that the SARs from children were lower than those from adults in household settings in the pre-Omicron era.7,8 The SARs of health care–associated SARS-CoV-2 infections among adult patients were reported as 12.3%–23.3%.3,4 However, the SAR in this pediatric study revealed a much lower rate. Whereas adult patients may ambulate and interact with one another within a shared room or ward, pediatric patients, particularly neonates and infants, are confined to fenced beds and are thus less mobile. Therefore, the probability of SARS-CoV-2 transmission within a hospital room may be lower in pediatric patients than in adult patients.
SARS-CoV-2 infection in children can result in severe clinical courses, such as pneumonia, myocarditis, and acute encephalopathy; however, such severe diseases are much less common than those in adults, and asymptomatic infections occur frequently due to the emergence of variants and the implementation of vaccinations.9,10 In the current study, the index and roommates with COVID-19 did not experience severe clinical course, and no further COVID-19 transmission was observed among the roommates. Given the relatively low risk of secondary transmission and severe disease, it is estimated that the risk of hospitalized children who contract SARS-CoV-2 developing severe disease is low. Taking these findings into account, cohort isolation of roommates to monitor the secondary attack of COVID-19 is no longer used in our hospital. In our opinion, active surveillance for asymptomatic SARS-CoV-2 infections is not an essential intervention for the children’s hospital infection control.
There are some limitations in this study. First, the transmission was not confirmed by strain level; thus, the homology of SARS-CoV-2 was not identified between the index case and their roommates. However, the study aimed rather to identify a practical strategy for hospital infection control. Second, this study was conducted at a single medical center with a relatively small sample size. Because the shared room spaces and the infection control protocols, such as when to use personal protective equipment and when to isolate SARS-CoV-2 cases, may vary among children’s hospitals, a multicenter study is necessary to validate the risk of secondary attack of COVID-19 in shared rooms among children. Third, the study lacked information regarding the vaccination history of the study subjects. However, given that the history of vaccination against SARS-CoV-2 did not influence the risk of secondary transmission in the household setting, it is presumed that the presence of vaccination history has a minimal impact on the findings of the present study.11 Lastly, the SAR in the current study may be overestimated. Because we did not account for asymptomatic shedding of SARS-CoV-2 from health care workers and family members, the SAR may include silent transmission from these individuals.
Conclusion
To our knowledge, this is the first report that analyzed the SAR of symptomatic SARS-CoV-2 infections among hospitalized children in shared rooms. The SAR in the largest tertiary children’s hospitals in Japan was not high in this current study. Given the estimated lower risk of SARS-CoV-2 transmission and the favorable clinical course of COVID-19 in children compared with adults, a pediatric-specific, effective infection prevention and surveillance strategy for COVID-19 should be established.
Dr Ikuse conceptualized and designed the study; led data collection, analysis, and interpretation; drafted the initial manuscript; reviewed and revised the manuscript; and approved the final manuscript as submitted. Dr Yamada supervised data collection, analysis, and interpretation; critically reviewed and revised the manuscript; and approved the final manuscript as submitted. Drs Kasai, Aiba, Matsui, Funaki, Shoji, and Ogimi contributed to the design of the study; supervised data interpretation; critically reviewed and revised the manuscript; and approved the final manuscript as submitted. Mses Kato, Miura, and Sugahara contributed to the study design and data interpretation and approved the final manuscript as submitted.
CONFLICT OF INTEREST DISCLOSURES: There are no conflicts of interest in this study.
FUNDING: This research received no specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Acknowledgments
We thank all NCCHD staff who cared for confirmed or suspected cases of SARS-CoV-2 infection.
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