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Investigating the relationship between interventions, contact patterns, and SARS-CoV-2 transmissibility.
Trentini, Filippo; Manna, Adriana; Balbo, Nicoletta; Marziano, Valentina; Guzzetta, Giorgio; O'Dell, Samantha; Kummer, Allisandra G; Litvinova, Maria; Merler, Stefano; Ajelli, Marco; Poletti, Piero; Melegaro, Alessia.
  • Trentini F; Dondena Centre for Research on Social Dynamics and Public Policy, Bocconi University, Milan, Italy; Covid Crisis Lab, Bocconi University, Italy; Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy. Electronic address: filippo.trentini@unibocconi.it.
  • Manna A; Dondena Centre for Research on Social Dynamics and Public Policy, Bocconi University, Milan, Italy; Department of Network and Data Science, Central European University, Wien, Austria.
  • Balbo N; Dondena Centre for Research on Social Dynamics and Public Policy, Bocconi University, Milan, Italy; Department of Social and Political Sciences, Bocconi University, Milan, Italy.
  • Marziano V; Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy.
  • Guzzetta G; Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy.
  • O'Dell S; Laboratory for Computational Epidemiology and Public Health, Department of Epidemiology and Biostatistics, Indiana University School of Public Health, Bloomington, IN, USA.
  • Kummer AG; Laboratory for Computational Epidemiology and Public Health, Department of Epidemiology and Biostatistics, Indiana University School of Public Health, Bloomington, IN, USA.
  • Litvinova M; Laboratory for Computational Epidemiology and Public Health, Department of Epidemiology and Biostatistics, Indiana University School of Public Health, Bloomington, IN, USA.
  • Merler S; Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy.
  • Ajelli M; Laboratory for Computational Epidemiology and Public Health, Department of Epidemiology and Biostatistics, Indiana University School of Public Health, Bloomington, IN, USA.
  • Poletti P; Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy.
  • Melegaro A; Dondena Centre for Research on Social Dynamics and Public Policy, Bocconi University, Milan, Italy; Covid Crisis Lab, Bocconi University, Italy; Department of Social and Political Sciences, Bocconi University, Milan, Italy. Electronic address: alessia.melegaro@unibocconi.it.
Epidemics ; 40: 100601, 2022 09.
Article in English | MEDLINE | ID: covidwho-1895034
ABSTRACT

BACKGROUND:

After a rapid upsurge of COVID-19 cases in Italy during the fall of 2020, the government introduced a three-tiered restriction system aimed at increasing physical distancing. The Ministry of Health, after periodic epidemiological risk assessments, assigned a tier to each of the 21 Italian regions and autonomous provinces. It is still unclear to what extent these different sets of measures altered the number of daily interactions and the social mixing patterns. METHODS AND

FINDINGS:

We conducted a survey between July 2020 and March 2021 to monitor changes in social contact patterns among individuals in the metropolitan city of Milan, Italy, which was hardly hit by the second wave of the COVID-19 pandemic. The number of daily contacts during periods characterized by different levels of restrictions was analyzed through negative binomial regression models and age-specific contact matrices were estimated under the different tiers of restrictions. By relying on the empirically estimated mixing patterns, we quantified relative changes in SARS-CoV-2 transmission potential associated with the different tiers. As tighter restrictions were implemented during the fall of 2020, a progressive reduction in the mean number of daily contacts recorded by study participants was observed from 15.9 % under mild restrictions (yellow tier), to 41.8 % under strong restrictions (red tier). Higher restrictions levels were also found to increase the relative contribution of contacts occurring within the household. The SARS-CoV-2 reproduction number was estimated to decrease by 17.1 % (95 %CI 1.5-30.1), 25.1 % (95 %CI 13.0-36.0) and 44.7 % (95 %CI 33.9-53.0) under the yellow, orange, and red tiers, respectively.

CONCLUSIONS:

Our results give an important quantification of the expected contribution of different restriction levels in shaping social contacts and decreasing the transmission potential of SARS-CoV-2. These estimates can find an operational use in anticipating the effect that the implementation of these tiered restriction can have on SARS-CoV-2 reproduction number under an evolving epidemiological situation.
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Full text: Available Collection: International databases Database: MEDLINE Main subject: SARS-CoV-2 / COVID-19 Type of study: Experimental Studies / Observational study / Prognostic study / Randomized controlled trials Limits: Humans Language: English Journal: Epidemics Year: 2022 Document Type: Article

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Full text: Available Collection: International databases Database: MEDLINE Main subject: SARS-CoV-2 / COVID-19 Type of study: Experimental Studies / Observational study / Prognostic study / Randomized controlled trials Limits: Humans Language: English Journal: Epidemics Year: 2022 Document Type: Article