Table 1 Summary of response interventions explored in the study

Self-isolation of symptomatic people

People with symptoms of possible COVID-19 isolate themselves in their home until symptom-free.

Relative reduction in all social contacts among symptomatic people only, during the period over which they are symptomatic.

0–100% relative reduction in transmission.

General physical distancing (including reduction of probability of transmission per contact)

Behaviour change, promotion of handwashing, varying degrees of curtailment of transport, social and work gatherings.

Relative reduction in contacts outside of the household.

0–100% relative reduction in transmission

(we assumed that ‘lockdown’ measures would correspond to an 80% reduction) [35].

Shielding of high-risk groups

Communities identify people who meet high-risk criteria for poor COVID-19 clinical outcomes and resettle them in a variety of shielded arrangements (either individual, e.g. a dedicated room within a house, or groups of various sizes in vacated / swapped houses, huts or other shelters). Contact is thereafter limited.

Within these shielded ‘green zones’, residents also adopt distancing and hygiene (handwashing, face coverings if locally appropriate) measures if they are living together.

A proportion of people aged ≥ 60 years old is ‘shielded’.

Contact between shielded people and unshielded people both inside and outside the household is reduced.

Contact among shielded people varies depending on the arrangement chosen.

60–100% of high-risk people are shielded.

60–100% relative reduction in contact with non-shielded people.

0–400% relative change in social contact among shielded people, compared to contacts among people eligible for shielding before they were shielded (0% represents individual shielding arrangements; 400% represents what might happen if people are grouped within overcrowded shielded housing).