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Research Letter
September 14, 2020

Frequency of Children vs Adults Carrying Severe Acute Respiratory Syndrome Coronavirus 2 Asymptomatically

Author Affiliations
  • 1Pediatric Emergency Department, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy
  • 2Department of Clinical Sciences and Community Health, Università degli Studi di Milano, Milan, Italy
  • 3Pediatric Highly Intensive Care Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy
  • 4Pediatric Intermediate Care Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy
  • 5Emergency Department, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy
JAMA Pediatr. 2021;175(2):193-194. doi:10.1001/jamapediatrics.2020.3595

Children have been suggested as the facilitators of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission and amplification,1 because many affected children might be asymptomatic.2,3 Accordingly, social and public health policies, such as school closure, have been implemented in many countries. However, the role of children in asymptomatically carrying SARS-CoV-2 needs to be further explored. In this study, we investigated the frequency of individuals carrying SARS-CoV-2 among children admitted for noninfectious conditions and without any SARS-CoV-2–associated symptoms or signs and compare it with the frequency of individuals carrying SARS-CoV-2 among a similar adult population.


At the Fondazione Ca’ Granda Ospedale Maggiore Policlinico in Milan, Italy, all patients who require hospitalization after accessing either the pediatric emergency department (for participants younger than 18 years) or the adult emergency department (for individuals 18 years and older) immediately undergo a nasopharyngeal swab for the detection of SARS-CoV-2, regardless of their symptoms. If the first sample has negative results, a second one is administered within 12 to 48 hours. For this study, eligible patients were those admitted for noninfectious conditions to this hospital from March 1 to April 30, 2020. We excluded individuals presenting with any signs or symptoms possibly associated with SARS-CoV-2 infection and those with a history of close and prolonged contact with individuals who had tested positive for SARS-CoV-2 or had a history of symptoms or signs consistent with COVID-19 in the previous 21 days. Individuals with only 1 nasopharyngeal swab available were also excluded. The Milano Area 2 ethics committee approved the study, which included a waiver of informed consent because of the retrospective nature of the investigation.

Data on age, sex, the reason for admission, and development of any SARS-CoV-2 signs of infection in the following 48 hours were retrospectively collected. A comparison of proportions between the pediatric and adult cohorts was made with the 2-tailed Fisher test. An odds ratio and its 95% CIs were calculated as a measure of risk of carrying SARS-CoV-2. Significance was assumed when P < .05. Statistical analysis was performed using the open-source statistical language R, version 3.5.3 (R Foundation for Statistical Computing).


In the study period, 881 children presented to the pediatric emergency department, and 83 children (34 girls and 49 boys; median [interquartile range] age, 5.3 [1.1-11.0] years) fulfilled the eligibility criteria. In the same period, among the 3610 adults presenting to the adult emergency department, 131 (51 women and 80 men; median [interquartile range] age, 77 [57-84] years) were included. The reasons for admission of the included individuals are given in the Table. Children were found to be less frequently positive than adults (1 in 83 children [1.2%] vs 12 in 131 adults [9.2%]; P = .02), with an odds ratio of 0.12 (95% CI, 0.02-0.95) compared with adults. Eleven of 12 adults were positive for SARS-CoV-2 at the first swab. None of the included individuals developed signs or symptoms of SARS-CoV-2 infection in the 48 hours after the admission.

Table.  Characteristics of the Included Children and Adults (N = 214)
Characteristics of the Included Children and Adults (N = 214)


In this study conducted among individuals hospitalized in Milan, one of the cities with the highest SARS-CoV-2 burden in the world, about 1% of children and 9% of adults without any symptoms or signs of SARS-CoV-2 infection tested positive for the virus. It has been estimated that approximately 80% of adults with SARS-CoV-2 are asymptomatic.4 The few available reports5 on children are from China and suggest that children who are asymptomatic might be 15% of individuals positive for SARS-CoV-2. In this study, children without symptoms and signs of SARS-CoV-2 carried the virus less frequently than adults, suggesting that their role as facilitators of the spreading of SARS-CoV-2 infection could be reconsidered. Along with this potential important implication, some limitations should be acknowledged: first, we retrospectively analyzed only cases requiring hospitalization, and second, we report a single-center experience. However, these preliminary results can help understanding the epidemiology of SARS-CoV-2 infections. Particularly, these data do not support the hypothesis that children are at higher risk of carrying SARS-CoV-2 asymptomatically than adults.

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Article Information

Accepted for Publication: May 26, 2020.

Corresponding Author: Carlo Agostoni, MD, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Via della Commenda 9, 20122 Milan, Italy (carlo.agostoni@unimi.it).

Published Online: September 14, 2020. doi:10.1001/jamapediatrics.2020.3595

Author Contributions: Drs Agostoni and Costantino had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the analysis.

Concept and design: Milani, Rocchi, Agostoni, Costantino.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Milani, Costantino.

Critical revision of the manuscript for important intellectual content: Bottino, Rocchi, Marchisio, Elli, Agostoni.

Statistical analysis: Milani.

Administrative, technical, or material support: Bottino, Rocchi, Elli.

Supervision: Marchisio, Agostoni, Costantino.

Conflict of Interest Disclosures: None reported.

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1 Comment for this article
COVID-19 Asymptomatic Children Versus Adults
Michael McAleer, PhD(Econometrics),Queen's | Asia University, Taiwan
Whether  children have a higher risk of being COVID-19 asymptomatic carriers than adults is an empirical issue, so the research findings from Milan, Italy for the 2-month period, 1 March to 30 April 2020, are highly informative.

The comparison was made between a sample of 83 children, with a mean age of 5.3 years, versus 131 adults, with a mean age of 77 years.

Given the age gap of almost three generations, conditioning on factors such as neurological or cardiac disease hardly seems necessary.

The striking primary finding that children are at not at a higher risk
than adults of carrying being asymptomatic carriers would be strengthened significantly by:

(1) follow-up analysis of the patients in the sample;

(2) extending the sample period beyond 30 April 2020;

(3) using data from a wide range of countries with varying stages of COVID-19 infections;

(4) using age cohorts that are much narrower, including teenagers, and young, medium aged and older adults;

(5) extending psychiatric disorders to include information on stress, anxiety, and mental health issues from prolonged and sustained social distancing, isolation, quarantining and lock downs;

(6) decomposing "other conditions" into drug taking and self harm.