The effectiveness of social bubbles as part of a Covid-19 lockdown exit strategy, a modelling study

Abstract

Background: ​ During the coronavirus disease 2019 (COVID-19) lockdown, contact clustering in social bubbles may allow extending contacts beyond the household at minimal additional risk and hence has been considered as part of modified lockdown policy or a gradual lockdown exit strategy. We estimated the impact of such strategies on epidemic and mortality risk using the UK as a case study. Methods: ​ We used an individual based model for a synthetic population similar to the UK, stratified into transmission risks from the community, within the household and from other households in the same social bubble. The base case considers a situation where non-essential shops and schools are closed, the secondary household attack rate is 20% and the initial reproduction number is 0.8. We simulate social bubble strategies (where two households form an exclusive pair) for households including children, for single occupancy households, and for all households. We test the sensitivity of results to a range of alternative model assumptions and parameters. Results: Clustering contacts outside the household into exclusive bubbles is an effective strategy of increasing contacts while limiting the associated increase in epidemic risk. In the base case, social bubbles reduced fatalities by 42% compared to an unclustered increase of contacts. We find that if all households were to form social bubbles the reproduction number would likely increase to above the epidemic threshold of R=1. Strategies allowing households with young children or single occupancy households to form social bubbles increased the reproduction number by less than 11%. The corresponding increase in mortality is proportional to the increase in the epidemic risk but is focussed in older adults irrespective of inclusion in social bubbles. Conclusions: ​ If managed appropriately, social bubbles can be an effective way of extending contacts beyond the household while limiting the increase in epidemic risk.

Ways of Being Together During the COVID-19 Pandemic: Support Bubbles and the Legal Construction of Relationships

“…Other countries, and particularly the United Kingdom, began looking to the concept of the bubble as part of lockdown easing strategies (Drakeford, 2020a;HM Government, 2020a). The aim was to permit increased contact, particularly for those identified as having the greatest need, while limiting the epidemic risk involved (Block et al, 2020;Leng et al, 2021). Bubbles were presented as a way of alleviating some of the worst effects of the loneliness, isolation, and separation involved in the original lockdowns.…”

“…332-333). It also revealed other base assumptions that underpinned modelling and policy in this context, such as about adherence, uptake, and engagement (Leng et al, 2021;Willem et al, 2021). More implicit assumptions were also included, such as that "people would automatically know what their bubbles would look like" and that those eligible to form cross-household bubbles had people in their lives with whom they could do so (Trnka and Davies, 2020).…”

Measuring close proximity interactions in summer camps during the COVID-19 pandemic

“…After this aggregation phase, the resulting contacts are enriched with metadata. For example, social bubbles [ 37 , 38 ] were enforced as a contagion containment measure, and thus we assign to each contact the groups of the two involved individuals. Further, each contact is associated with the activity being performed during the contact time.…”

“…In particular, we study the distribution of the level of contagion risk among individuals depending on the proximity and duration of their contacts, finding that a vast majority of CPIs are classified as low risk. Moreover, we aggregate the contacts as intra-group (i.e., within the social bubble) and inter-group (i.e., between different bubbles), and observe changes in the distribution of contact risk levels in the two cases, offering evidence of the effectiveness of the social bubble strategy [ 37 , 38 ]. Finally, a thorough analysis of the different activities provides insights into their inherent risks of contagion, which can be further interpreted in view of the features of the activity itself (indoor or outdoor, static or dynamic, etc.).…”

Segregation of children into small groups for in-person learning during the COVID-19 pandemic

“…In the UK, the Department of Education asked schools to keep children in unmixed groups or bubbles, although later they removed this recommendation (20). Modeling studies on social segregation into groups controls for a rapid increase of COVID-19 infections (21,22), but the effectiveness of segregating school communities into bubbles in mitigating the propagation of the COVID-19 disease and its impact on the operation of in-person learning programs has not been studied in detail. Moreover, it is unclear how such a strategy performs under different conditions, such as varying the size of the bubble or allowing children within a bubble not to obey social distancing or facemask wearing.…”