Numbers of close contacts of individuals infected with SARS-CoV-2 and their association with government intervention strategies
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Abstract
Background
Contact tracing is conducted with the primary purpose of interrupting transmission from individuals who are likely to be infectious to others. Secondary analyses of data on the numbers of close contacts of confirmed cases could also: provide an early signal of increases in contact patterns that might precede larger than expected case numbers; evaluate the impact of government interventions on the number of contacts of confirmed cases; or provide data information on contact rates between age cohorts for the purpose of epidemiological modelling. We analysed data from 140,204 close contacts of 39,861 cases in Ireland from 1st May to 1st December 2020.
Results
Negative binomial regression models highlighted greater numbers of contacts within specific population demographics, after correcting for temporal associations. Separate segmented regression models of the number of cases over time and the average number of contacts per case indicated that a breakpoint indicating a rapid decrease in the number of contacts per case in October 2020 preceded a breakpoint indicating a reduction in the number of cases by 11 days.
Conclusions
We found that the number of contacts per infected case was overdispersed, the mean varied considerable over time and was temporally associated with government interventions. Analysis of the reported number of contacts per individual in contact tracing data may be a useful early indicator of changes in behaviour in response to, or indeed despite, government restrictions. This study provides useful information for triangulating assumptions regarding the contact mixing rates between different age cohorts for epidemiological modelling.
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SciScore for 10.1101/2021.01.20.21250109: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement IRB: The study was approved by both the National Research Ethics Committee (20-NREC-COV-099) and the Health Research Consent Declaration Committee (20-025-AF1/COV) since the data were used for a purpose other than that for which it was initially collected and since it was not possible to retrospectively obtain consent.
Consent: The study was approved by both the National Research Ethics Committee (20-NREC-COV-099) and the Health Research Consent Declaration Committee (20-025-AF1/COV) since the data were used for a purpose other than that for which it was initially collected and since it was not possible to retrospectively obtain consent.Randomization not detected. SciScore for 10.1101/2021.01.20.21250109: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement IRB: The study was approved by both the National Research Ethics Committee (20-NREC-COV-099) and the Health Research Consent Declaration Committee (20-025-AF1/COV) since the data were used for a purpose other than that for which it was initially collected and since it was not possible to retrospectively obtain consent.
Consent: The study was approved by both the National Research Ethics Committee (20-NREC-COV-099) and the Health Research Consent Declaration Committee (20-025-AF1/COV) since the data were used for a purpose other than that for which it was initially collected and since it was not possible to retrospectively obtain consent.Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. Table 2: Resources
No key resources detected.
Results from OddPub: Thank you for sharing your data.
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:A number of limitations must be considered when considering this study. Firstly, it must be remembered that these contact rates are of those that were infected with SARS-CoV-2 at particular points in time; that is, they are not a random sample from the population. Therefore, care is needed in interpretation, in particular when examining temporal associations. For example, at particular points in time in Ireland, older individuals were overrepresented in the numbers of cases. The contacts from these individuals might be expected to be less than in other age cohorts, with many of the most elderly in long term care facilities, and this could be associated temporally with a particular government intervention. As a consequence, changes, for example a reduction, in the average number of contacts could largely be a consequence of changes to case demographics rather than as a result of government restrictions. However, regional comparison of contact number suggests this is not a significant factor. For example, Figure 1 shows that contacts per case fell much faster in Dublin than the rest of the country following the introduction of regional Level 3 restrictions. Following this, Level 3 was extended nationally, with a corresponding rapid drop in contacts per case across the rest of the country. Furthermore, whilst the number of contacts per case is not representative of the overall population, they are representative of the individuals who were infected at that point in time. Therefo...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
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