Time use and social mixing during and around festive periods: Potential changes in the age distribution of COVID-19 cases from increased intergenerational interactions

  1. Edwin van Leeuwen
  2. Frank G. Sandmann
  3. Rosalind M. Eggo
  4. PHE Joint modelling group
  5. Peter J. White

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Abstract

Rationale

Amid the ongoing coronavirus disease 2019 (COVID-19) pandemic in which many countries have adopted physical distancing measures, tiered restrictions, and episodic “lockdowns,” the impact of potentially increased social mixing during festive holidays on the age distribution of new COVID-19 cases remains unclear.

Objective

We aimed to gain insights into possible changes in the age distribution of COVID-19 cases in the UK after temporarily increased intergenerational interactions in late December 2020.

Method

We modelled changes in time use and social mixing based on age-stratified contact rates using historical nationally-representative surveys and up-to-date Google mobility data from four weeks before and after the festive period. We explored changes in the effective reproduction number and the age distribution of cases, in four scenarios: (1) “normal”: time use and contact patterns as observed historically, (2) “pre-lockdown”: patterns as seen before the lockdown in November 2020, (3) “lockdown”: patterns restricted as in November 2020, and (4) “festive break”: similar to 3 but with social visits over the holiday period as in 1.

Results

Across ages, the estimated R eff decreases during the festive break in scenarios 1-3 and returns to pre-holiday levels in scenarios 2-3, while remaining relatively stable in scenario 4. Relative incidence is likely to decrease in children aged 0-15 but increase in other ages. Changes in age distribution were large during the holidays, and are likely to start before the holidays for individuals aged 16-24 years in scenarios 1-3.

Conclusions

Our modelling findings suggest that increased contacts during the festive period may shift the age distribution of COVID-19 cases from children towards adults. Given that COVID-19-related hospitalisations and deaths rise by age, more intergenerational mixing risks an increased burden in the period following the holidays.

Highlights

  • Home visits are associated with increased intergenerational mixing.

  • The effective reproduction number is likely to remain stable or even reduce slightly due to a reduction in contacts at work and school.

  • Relative incidence is likely to become lower in children, but higher in the

  • older (more vulnerable) age groups around the holiday period, which could lead to increased health care burden.

Article activity feed

  1. ScreenIT

    SciScore for 10.1101/2020.12.21.20248607: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Strengths and Limitations: Our study used nationally-representative survey data and population-level mobility data in a transmission-dynamic compartmental model to explore changes in behaviour and the impact on new COVID-19 cases. This work built on our previous work (van Leeuwen, PHE Joint modelling group, and Sandmann 2020), and preliminary findings were presented to UK scientific advisers to highlight possible scenarios for the festive period in December 2020. In the absence of being able to robustly predict the behaviour of individuals during a major festive holiday in the UK, our study needed to make assumptions about time use and its effect on contact patterns that reflect the historic survey data. The mapping from time use to number of contacts assumes that time use is proportional to number of contacts during that activity, which may not hold for specific settings such as during social visits and in bars and restaurants. Also, our analysis did not explicitly capture the effect of individuals moving between geographical locations and/or potentially changing the composition of their social circles over Christmas, or the potential effects of forming social bubbles over the holiday period. Similar changes have been reported during the summer holidays in the UK in 2020, with Facebook population movement decreasing in more densely populated areas and increasing in rural areas that are popular holiday destinations; however, the movement in areas of localised lockdowns decrea...

    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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  2. Version published to 10.1101/2020.12.21.20248607v1 on medRxiv