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Association of Age With Likelihood of Developing Symptoms and Critical Disease Among Close Contacts Exposed to Patients With Confirmed SARS-CoV-2 Infection in Italy.
JAMA Netw Open. 2021 03 01; 4(3):e211085.JN

Abstract

Importance

Solid estimates of the risk of developing symptoms and of progressing to critical disease in individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are key to interpreting coronavirus disease 2019 (COVID-19) dynamics, identifying the settings and the segments of the population where transmission is more likely to remain undetected, and defining effective control strategies.

Objective

To estimate the association of age with the likelihood of developing symptoms and the association of age with the likelihood of progressing to critical illness after SARS-CoV-2 infection.

Design, Setting, and Participants

This cohort study analyzed quarantined case contacts, identified between February 20 and April 16, 2020, in the Lombardy region of Italy. Contacts were monitored daily for symptoms and tested for SARS-CoV-2 infection, by either real-time reverse transcriptase-polymerase chain reaction using nasopharyngeal swabs or retrospectively via IgG serological assays. Close contacts of individuals with laboratory-confirmed COVID-19 were selected as those belonging to clusters (ie, groups of contacts associated with an index case) where all individuals were followed up for symptoms and tested for SARS-CoV-2 infection. Data were analyzed from February to June 2020.

Exposure

Close contact with individuals with confirmed COVID-19 cases as identified by contact tracing operations.

Main Outcomes and Measures

Age-specific estimates of the risk of developing respiratory symptoms or fever greater than or equal to 37.5 °C and of experiencing critical disease (defined as requiring intensive care or resulting in death) in SARS-CoV-2-infected case contacts.

Results

In total, 5484 case contacts (median [interquartile range] age, 50 [30-61] years; 3086 female contacts [56.3%]) were analyzed, 2824 of whom (51.5%) tested positive for SARS-CoV-2 (median [interquartile range] age, 53 [34-64] years; 1604 female contacts [56.8%]). The proportion of infected persons who developed symptoms ranged from 18.1% (95% CI, 13.9%-22.9%) among participants younger than 20 years to 64.6% (95% CI, 56.6%-72.0%) for those aged 80 years or older. Most infected contacts (1948 of 2824 individuals [69.0%]) did not develop respiratory symptoms or fever greater than or equal to 37.5 °C. Only 26.1% (95% CI, 24.1%-28.2%) of infected individuals younger than 60 years developed respiratory symptoms or fever greater than or equal to 37.5 °C; among infected participants older than 60 years, 6.6% (95% CI, 5.1%-8.3%) developed critical disease. Female patients were 52.7% (95% CI, 24.4%-70.7%) less likely than male patients to develop critical disease after SARS-CoV-2 infection.

Conclusions and Relevance

In this Italian cohort study of close contacts of patients with confirmed SARS-CoV-2 infection, more than one-half of individuals tested positive for the virus. However, most infected individuals did not develop respiratory symptoms or fever. The low proportion of children and young adults who developed symptoms highlights the possible challenges in readily identifying SARS-CoV-2 infections.

Authors+Show Affiliations

Fondazione Bruno Kessler, Povo, Trento, Italy.Directorate General for Health, Lombardy Region, Milan, Italy. Health Protection Agency of Pavia, Pavia, Italy.Directorate General for Health, Lombardy Region, Milan, Italy.Fondazione Bruno Kessler, Povo, Trento, Italy.Fondazione Bruno Kessler, Povo, Trento, Italy.Directorate General for Health, Lombardy Region, Milan, Italy.Fondazione Bruno Kessler, Povo, Trento, Italy.Department of Biomedical Sciences for Health, University of Milan, Milan, Italy.Department of Biomedical Sciences for Health, University of Milan, Milan, Italy.Department of Biomedical Sciences for Health, University of Milan, Milan, Italy.Dondena Centre for Research on Social Dynamics and Public Policy, Bocconi University, Milan, Italy. Department of Decision Sciences, Bocconi University, Milan, Italy. CovidCrisisLab, Bocconi University, Milan, Italy.Directorate General for Health, Lombardy Region, Milan, Italy.Dondena Centre for Research on Social Dynamics and Public Policy, Bocconi University, Milan, Italy. CovidCrisisLab, Bocconi University, Milan, Italy. Department of Social and Political Sciences, Bocconi University, Milan, Italy.Directorate General for Health, Lombardy Region, Milan, Italy.Department of Epidemiology and Biostatistics, Indiana University School of Public Health, Bloomington. Laboratory for the Modeling of Biological and Socio-technical Systems, Northeastern University, Boston, Massachusetts.Fondazione Bruno Kessler, Povo, Trento, Italy.No affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

33688964

Citation

Poletti, Piero, et al. "Association of Age With Likelihood of Developing Symptoms and Critical Disease Among Close Contacts Exposed to Patients With Confirmed SARS-CoV-2 Infection in Italy." JAMA Network Open, vol. 4, no. 3, 2021, pp. e211085.
Poletti P, Tirani M, Cereda D, et al. Association of Age With Likelihood of Developing Symptoms and Critical Disease Among Close Contacts Exposed to Patients With Confirmed SARS-CoV-2 Infection in Italy. JAMA Netw Open. 2021;4(3):e211085.
Poletti, P., Tirani, M., Cereda, D., Trentini, F., Guzzetta, G., Sabatino, G., Marziano, V., Castrofino, A., Grosso, F., Del Castillo, G., Piccarreta, R., Andreassi, A., Melegaro, A., Gramegna, M., Ajelli, M., & Merler, S. (2021). Association of Age With Likelihood of Developing Symptoms and Critical Disease Among Close Contacts Exposed to Patients With Confirmed SARS-CoV-2 Infection in Italy. JAMA Network Open, 4(3), e211085. https://doi.org/10.1001/jamanetworkopen.2021.1085
Poletti P, et al. Association of Age With Likelihood of Developing Symptoms and Critical Disease Among Close Contacts Exposed to Patients With Confirmed SARS-CoV-2 Infection in Italy. JAMA Netw Open. 2021 03 1;4(3):e211085. PubMed PMID: 33688964.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Association of Age With Likelihood of Developing Symptoms and Critical Disease Among Close Contacts Exposed to Patients With Confirmed SARS-CoV-2 Infection in Italy. AU - Poletti,Piero, AU - Tirani,Marcello, AU - Cereda,Danilo, AU - Trentini,Filippo, AU - Guzzetta,Giorgio, AU - Sabatino,Giuliana, AU - Marziano,Valentina, AU - Castrofino,Ambra, AU - Grosso,Francesca, AU - Del Castillo,Gabriele, AU - Piccarreta,Raffaella, AU - Andreassi,Aida, AU - Melegaro,Alessia, AU - Gramegna,Maria, AU - Ajelli,Marco, AU - Merler,Stefano, AU - ,, Y1 - 2021/03/01/ PY - 2021/3/10/entrez PY - 2021/3/11/pubmed PY - 2021/3/19/medline SP - e211085 EP - e211085 JF - JAMA network open JO - JAMA Netw Open VL - 4 IS - 3 N2 - Importance: Solid estimates of the risk of developing symptoms and of progressing to critical disease in individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are key to interpreting coronavirus disease 2019 (COVID-19) dynamics, identifying the settings and the segments of the population where transmission is more likely to remain undetected, and defining effective control strategies. Objective: To estimate the association of age with the likelihood of developing symptoms and the association of age with the likelihood of progressing to critical illness after SARS-CoV-2 infection. Design, Setting, and Participants: This cohort study analyzed quarantined case contacts, identified between February 20 and April 16, 2020, in the Lombardy region of Italy. Contacts were monitored daily for symptoms and tested for SARS-CoV-2 infection, by either real-time reverse transcriptase-polymerase chain reaction using nasopharyngeal swabs or retrospectively via IgG serological assays. Close contacts of individuals with laboratory-confirmed COVID-19 were selected as those belonging to clusters (ie, groups of contacts associated with an index case) where all individuals were followed up for symptoms and tested for SARS-CoV-2 infection. Data were analyzed from February to June 2020. Exposure: Close contact with individuals with confirmed COVID-19 cases as identified by contact tracing operations. Main Outcomes and Measures: Age-specific estimates of the risk of developing respiratory symptoms or fever greater than or equal to 37.5 °C and of experiencing critical disease (defined as requiring intensive care or resulting in death) in SARS-CoV-2-infected case contacts. Results: In total, 5484 case contacts (median [interquartile range] age, 50 [30-61] years; 3086 female contacts [56.3%]) were analyzed, 2824 of whom (51.5%) tested positive for SARS-CoV-2 (median [interquartile range] age, 53 [34-64] years; 1604 female contacts [56.8%]). The proportion of infected persons who developed symptoms ranged from 18.1% (95% CI, 13.9%-22.9%) among participants younger than 20 years to 64.6% (95% CI, 56.6%-72.0%) for those aged 80 years or older. Most infected contacts (1948 of 2824 individuals [69.0%]) did not develop respiratory symptoms or fever greater than or equal to 37.5 °C. Only 26.1% (95% CI, 24.1%-28.2%) of infected individuals younger than 60 years developed respiratory symptoms or fever greater than or equal to 37.5 °C; among infected participants older than 60 years, 6.6% (95% CI, 5.1%-8.3%) developed critical disease. Female patients were 52.7% (95% CI, 24.4%-70.7%) less likely than male patients to develop critical disease after SARS-CoV-2 infection. Conclusions and Relevance: In this Italian cohort study of close contacts of patients with confirmed SARS-CoV-2 infection, more than one-half of individuals tested positive for the virus. However, most infected individuals did not develop respiratory symptoms or fever. The low proportion of children and young adults who developed symptoms highlights the possible challenges in readily identifying SARS-CoV-2 infections. SN - 2574-3805 UR - https://www.unboundmedicine.com/medline/citation/33688964/Association_of_Age_With_Likelihood_of_Developing_Symptoms_and_Critical_Disease_Among_Close_Contacts_Exposed_to_Patients_With_Confirmed_SARS_CoV_2_Infection_in_Italy_ L2 - https://jamanetwork.com/journals/jamanetworkopen/fullarticle/10.1001/jamanetworkopen.2021.1085 DB - PRIME DP - Unbound Medicine ER -