Association of Age and Pediatric Household Transmission of SARS-CoV-2 Infection | Infectious Diseases | JN Learning | AMA Ed Hub [Skip to Content]
[Skip to Content Landing]

Association of Age and Pediatric Household Transmission of SARS-CoV-2 Infection

Educational Objective
To identify the key insights or developments described in this article
1 Credit CME
Key Points

Question  Are there differences in the odds of household transmission of SARS-CoV-2 by younger children compared with older children?

Findings  In this cohort study of 6280 households with pediatric index cases, the adjusted odds of household transmission by children aged 0 to 3 years was 1.43 compared with children aged 14 to 17 years.

Meaning  Younger children may have greater risk of transmitting SARS-CoV-2 to caregivers and siblings in the household than older children.


Importance  As a result of low numbers of pediatric cases early in the COVID-19 pandemic, pediatric household transmission of SARS-CoV-2 remains an understudied topic.

Objective  To determine whether there are differences in the odds of household transmission by younger children compared with older children.

Design, Setting, and Participants  This population-based cohort study took place between June 1 and December 31, 2020, in Ontario, Canada. Private households in which the index case individual of laboratory-confirmed SARS-CoV-2 infection was younger than 18 years were included. Individuals were excluded if they resided in apartments missing suite information, in households with multiple index cases, or in households where the age of the index case individual was missing.

Exposures  Age group of pediatric index cases categorized as 0 to 3, 4 to 8, 9 to 13, and 14 to 17 years.

Main Outcomes and Measures  Household transmission, defined as households where at least 1 secondary case occurred 1 to 14 days after the pediatric index case.

Results  A total of 6280 households had pediatric index cases, and 1717 households (27.3%) experienced secondary transmission. The mean (SD) age of pediatric index case individuals was 10.7 (5.1) years and 2863 (45.6%) were female individuals. Children aged 0 to 3 years had the highest odds of transmitting SARS-CoV-2 to household contacts compared with children aged 14 to 17 years (odds ratio, 1.43; 95% CI, 1.17-1.75). This association was similarly observed in sensitivity analyses defining secondary cases as 2 to 14 days or 4 to 14 days after the index case and stratified analyses by presence of symptoms, association with a school/childcare outbreak, or school/childcare reopening. Children aged 4 to 8 years and 9 to 13 years also had increased odds of transmission (aged 4-8 years: odds ratio, 1.40; 95% CI, 1.18-1.67; aged 9-13 years: odds ratio, 1.13; 95% CI, 0.97-1.32).

Conclusions and Relevance  This study suggests that younger children may be more likely to transmit SARS-CoV-2 infection compared with older children, and the highest odds of transmission was observed for children aged 0 to 3 years. Differential infectivity of pediatric age groups has implications for infection prevention within households, as well as schools/childcare, to minimize risk of household secondary transmission. Additional population-based studies are required to establish the risk of transmission by younger pediatric index cases.

Sign in to take quiz and track your certificates

Buy This Activity

JN Learning™ is the home for CME and MOC from the JAMA Network. Search by specialty or US state and earn AMA PRA Category 1 CME Credit™ from articles, audio, Clinical Challenges and more. Learn more about CME/MOC

CME Disclosure Statement: Unless noted, all individuals in control of content reported no relevant financial relationships. If applicable, all relevant financial relationships have been mitigated.

Article Information

Corresponding Author: Sarah A. Buchan, PhD, Public Health Ontario, 661 University Ave, Floor 17, Toronto, ON M5G 1M1, Canada (

Accepted for Publication: May 19, 2021.

Published Online: August 16, 2021. doi:10.1001/jamapediatrics.2021.2770

Correction: This article was corrected on September 20 2021, to fix a typo in Table 2.

Author Contributions: Ms Paul and Dr Buchan 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 data analysis.

Concept and design: Paul, Daneman, Schwartz, Science, Brown, Buchan.

Acquisition, analysis, or interpretation of data: Paul, Schwartz, Science, Brown, Whelan, Chan, Buchan.

Drafting of the manuscript: Paul.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Paul, Schwartz, Brown.

Administrative, technical, or material support: Paul, Schwartz, Buchan.

Supervision: Science, Buchan.

Conflict of Interest Disclosures: Dr Buchan reported grants from Canadian Institutes of Health Research for research on influenza, respiratory syncytial virus, and COVID-19 and grants from Canadian Immunity Task Force for COVID-19 vaccines outside the submitted work. No other disclosures were reported.

Funding/Support: This study did not have a direct funding source but was supported by Public Health Ontario.

Role of the Funder/Sponsor: The sponsor had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Additional Contributions: We thank James Johnson, MPH, and Arezou Saedi, MD, for conducting the address-matching work; Trevor van Ingen, MPH, for providing the neighborhood-level data; and Semra Tibebu, MPH, for cleaning the individual-level household size variable. These individuals made their contributions as part of their roles as paid employees of Public Health Ontario at the time of the study.

Zhang  J , Litvinova  M , Liang  Y ,  et al.  Changes in contact patterns shape the dynamics of the COVID-19 outbreak in China.   Science. 2020;368(6498):1481-1486. doi:10.1126/science.abb8001PubMedGoogle ScholarCrossref
Zhu  Y , Bloxham  CJ , Hulme  KD ,  et al.  A meta-analysis on the role of children in severe acute respiratory syndrome coronavirus 2 in household transmission clusters.   Clin Infect Dis. 2021;72(12):e1146-e1153. doi:10.1093/cid/ciaa1825PubMedGoogle ScholarCrossref
Chang  T-H , Wu  J-L , Chang  L-Y .  Clinical characteristics and diagnostic challenges of pediatric COVID-19: a systematic review and meta-analysis.   J Formos Med Assoc. 2020;119(5):982-989. doi:10.1016/j.jfma.2020.04.007PubMedGoogle ScholarCrossref
Hyde  Z .  Difference in SARS-CoV-2 attack rate between children and adults may reflect bias.   Clin Infect Dis. 2021;ciab183. doi:10.1093/cid/ciab183PubMedGoogle Scholar
Goldstein  E , Lipsitch  M , Cevik  M .  On the effect of age on the transmission of SARS-CoV-2 in households, schools and the community.   medRxiv. Preprint posted July 28, 2020. doi:10.1101/2020.07.19.20157362Google Scholar
van der Hoek  W , Backer  JA , Bodewes  R ,  et al.  De rol van kinderen in de transmissie van SARS-CoV-2.   Ned Tijdschr Geneeskd. 2020;164(25):D5140.PubMedGoogle Scholar
Ludvigsson  JF .  Children are unlikely to be the main drivers of the COVID-19 pandemic: a systematic review.   Acta Paediatr. 2020;109(8):1525-1530. doi:10.1111/apa.15371PubMedGoogle ScholarCrossref
Arnedo-Pena  A , Sabater-Vidal  S , Meseguer-Ferrer  N ,  et al  COVID-19 secondary attack rate and risk factors in household contacts in Castellon (Spain): preliminary report.   Rev Enf Emerg. 2020;19(2):64-70.Google Scholar
Jing  Q-L , Liu  M-J , Zhang  Z-B ,  et al.  Household secondary attack rate of COVID-19 and associated determinants in Guangzhou, China: a retrospective cohort study.   Lancet Infect Dis. 2020;20(10):1141-1150. doi:10.1016/S1473-3099(20)30471-0PubMedGoogle ScholarCrossref
Dattner  I , Goldberg  Y , Katriel  G ,  et al  The role of children in the spread of COVID-19: using household data from Bnei Brak, Israel, to estimate the relative susceptibility and infectivity of children.   medRxiv. Preprint posted October 11, 2020. doi:10.1101/2020.06.03.20121145Google Scholar
Sun  K , Wang  W , Gao  L ,  et al.  Transmission heterogeneities, kinetics, and controllability of SARS-CoV-2.   Science. 2021;371(6526):eabe2424. doi:10.1126/science.abe2424PubMedGoogle Scholar
Li  F , Li  Y-Y , Liu  M-J ,  et al.  Household transmission of SARS-CoV-2 and risk factors for susceptibility and infectivity in Wuhan: a retrospective observational study.   Lancet Infect Dis. 2021;21(5):617-628. doi:10.1016/S1473-3099(20)30981-6PubMedGoogle ScholarCrossref
Xin  H , Jiang  F , Xue  A ,  et al.  Risk factors associated with occurrence of COVID-19 among household persons exposed to patients with confirmed COVID-19 in Qingdao Municipal, China.   Transbound Emerg Dis. 2021;68(2):782-788. doi:10.1111/tbed.13743PubMedGoogle ScholarCrossref
Wu  J , Huang  Y , Tu  C ,  et al.  Household transmission of SARS-CoV-2, Zhuhai, China, 2020.   Clin Infect Dis. 2020;71(16):2099-2108. doi:10.1093/cid/ciaa557PubMedGoogle ScholarCrossref
Thompson  HA , Mousa  A , Dighe  A ,  et al.  SARS-CoV-2 setting-specific transmission rates: a systematic review and meta-analysis.   Clin Infect Dis. Published online February 9, 2021. doi:10.1093/cid/ciab100Google Scholar
Soriano-Arandes  A , Gatell  A , Serrano  P ,  et al; COPEDI-CAT research group.  Household SARS-CoV-2 transmission and children: a network prospective study.   Clin Infect Dis. 2021;ciab228. doi:10.1093/cid/ciab228PubMedGoogle Scholar
Bi  Q , Wu  Y , Mei  S ,  et al.  Epidemiology and transmission of COVID-19 in 391 cases and 1286 of their close contacts in Shenzhen, China: a retrospective cohort study.   Lancet Infect Dis. 2020;20(8):911-919. doi:10.1016/S1473-3099(20)30287-5PubMedGoogle ScholarCrossref
Wang  Y , Tian  H , Zhang  L ,  et al.  Reduction of secondary transmission of SARS-CoV-2 in households by face mask use, disinfection and social distancing: a cohort study in Beijing, China.   BMJ Glob Health. 2020;5(5):e002794. doi:10.1136/bmjgh-2020-002794PubMedGoogle Scholar
Hu  S , Wang  W , Wang  Y ,  et al  Infectivity, susceptibility, and risk factors associated with SARS-CoV-2 transmission under intensive contact tracing in Hunan, China.   medRxiv. Preprint posted November 3, 2020. doi:10.1101/2020.07.23.20160317Google Scholar
Park  YJ , Choe  YJ , Park  O ,  et al; COVID-19 National Emergency Response Center, Epidemiology and Case Management Team.  Contact tracing during coronavirus disease outbreak, South Korea, 2020.   Emerg Infect Dis. 2020;26(10):2465-2468. doi:10.3201/eid2610.201315PubMedGoogle ScholarCrossref
Lyngse  FP , Kirkeby  CT , Halasa  T ,  et al  COVID-19 transmission within Danish households: A nationwide study from lockdown to reopening.   medRxiv. 2020. doi:10.1101/2020.09.09.20191239Google Scholar
Lyngse  FP , Mølbak  K , Frank  KT , Nielsen  C , Skov  RL , Kirkeby  CT .  Association between SARS-CoV-2 transmission risk, viral load, and age: a nationwide study in Danish households.   medRxiv. 2021. doi:10.1101/2021.02.28.21252608Google Scholar
Grijalva  CG , Rolfes  MA , Zhu  Y ,  et al.  Transmission of SARS-COV-2 infections in households: Tennessee and Wisconsin, April-September 2020.   MMWR Morb Mortal Wkly Rep. 2020;69(44):1631-1634. doi:10.15585/mmwr.mm6944e1PubMedGoogle ScholarCrossref
Koh  WC , Naing  L , Chaw  L ,  et al.  What do we know about SARS-CoV-2 transmission? a systematic review and meta-analysis of the secondary attack rate and associated risk factors.   PLoS One. 2020;15(10):e0240205. doi:10.1371/journal.pone.0240205PubMedGoogle Scholar
Paul  LA , Daneman  N , Brown  KA ,  et al.  Characteristics associated with household transmission of SARS-CoV-2 in Ontario, Canada: a cohort study.   Clin Infect Dis. 2021;ciab186. doi:10.1093/cid/ciab186PubMedGoogle Scholar
Maltezou  HC , Vorou  R , Papadima  K ,  et al.  Transmission dynamics of SARS-CoV-2 within families with children in Greece: a study of 23 clusters.   J Med Virol. 2021;93(3):1414-1420. doi:10.1002/jmv.26394PubMedGoogle ScholarCrossref
Posfay-Barbe  KM , Wagner  N , Gauthey  M ,  et al.  COVID-19 in children and the dynamics of infection in families.   Pediatrics. 2020;146(2):e20201576. doi:10.1542/peds.2020-1576PubMedGoogle Scholar
Marks  M , Millat-Martinez  P , Ouchi  D ,  et al.  Transmission of COVID-19 in 282 clusters in Catalonia, Spain: a cohort study.   Lancet Infect Dis. 2021;21(5):629-636. doi:10.1016/S1473-3099(20)30985-3PubMedGoogle ScholarCrossref
Lee  LYW , Rozmanowski  S , Matthew  P ,  et al.  SARS-CoV-2 infectivity by viral load, S gene variants and demographic factors and the utility of lateral flow devices to prevent transmission.   Clin Infect Dis. Published online May 11, 2021. doi:10.1093/cid/ciab421Google Scholar
Heald-Sargent  T , Muller  WJ , Zheng  X , Rippe  J , Patel  AB , Kociolek  LK .  Age-related differences in nasopharyngeal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) levels in patients with mild to moderate coronavirus disease 2019 (COVID-19).   JAMA Pediatr. 2020;174(9):902-903. doi:10.1001/jamapediatrics.2020.3651PubMedGoogle ScholarCrossref
Jones  TC , Mühlemann  B , Veith  T ,  et al  An analysis of SARS-CoV-2 viral load by patient age.   medRxiv. Preprint posted June 9, 2020. doi:10.1101/2020.06.08.20125484Google Scholar
Yonker  LM , Neilan  AM , Bartsch  Y ,  et al.  Pediatric severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2): Clinical presentation, infectivity, and immune responses.   J Pediatr. 2020;227:45-52.e5. doi:10.1016/j.jpeds.2020.08.037PubMedGoogle ScholarCrossref
L’Huillier  AG , Torriani  G , Pigny  F , Kaiser  L , Eckerle  I .  Culture-competent SARS-CoV-2 in nasopharynx of symptomatic neonates, children, and adolescents.   Emerg Infect Dis. 2020;26(10):2494-2497. doi:10.3201/eid2610.202403PubMedGoogle ScholarCrossref
Bullard  J , Funk  D , Dust  K ,  et al.  Infectivity of severe acute respiratory syndrome coronavirus 2 in children compared with adults.   CMAJ. 2021;193(17):E601-E606. doi:10.1503/cmaj.210263PubMedGoogle ScholarCrossref
Lewis  NM , Duca  LM , Marcenac  P ,  et al.  Characteristics and timing of initial virus shedding in severe acute respiratory syndrome coronavirus 2, Utah, USA.   Emerg Infect Dis. 2021;27(2):352-359. doi:10.3201/eid2702.203517PubMedGoogle ScholarCrossref
Want full access to the AMA Ed Hub?
After you sign up for AMA Membership, make sure you sign in or create a Physician account with the AMA in order to access all learning activities on the AMA Ed Hub
Buy this activity
Want full access to the AMA Ed Hub?
After you sign up for AMA Membership, make sure you sign in or create a Physician account with the AMA in order to access all learning activities on the AMA Ed Hub
Buy this activity
With a personal account, you can:
  • Access free activities and track your credits
  • Personalize content alerts
  • Customize your interests
  • Fully personalize your learning experience
Education Center Collection Sign In Modal Right

Name Your Search

Save Search
With a personal account, you can:
  • Access free activities and track your credits
  • Personalize content alerts
  • Customize your interests
  • Fully personalize your learning experience

Lookup An Activity



My Saved Searches

You currently have no searches saved.


My Saved Courses

You currently have no courses saved.

With a personal account, you can:
  • Access free activities and track your credits
  • Personalize content alerts
  • Customize your interests
  • Fully personalize your learning experience
Education Center Collection Sign In Modal Right