A combination of robust vaccination programs and strict physical distancing rules could avoid recurring peaks of COVID-19 without the need to rely on stay-at-home restrictions, according to a new study by epidemiologists and demographers from WorldPop at the University of Southampton, in collaboration with The Chinese University of Hong Kong.

This research used anonymized mobile phone geolocation data with epidemiological and coronavirus case data from China to model the potential impact of vaccination and physical distancing on virus transmission. They predicted the effect of different combinations of interventions on low, medium and high density cities in the country.

The impact of physical distancing in containing future resurgences of COVID-19 depends greatly on the intensity of measures, population density, and the availability of vaccines across geographical areas and time. The researchers set out to gain a greater understanding of the relationship between these factors.

The findings are published in the journal Nature Human Behaviour.

The team predicts that in most cities, vaccination programmes and physical distancing combined will be enough to contain virus resurgence without the need to greatly restrict population mobility. Containment in this study was defined as maintaining a low transmission rate, or 'R' below one.

The researchers report cities with medium and high density populations will need both vaccination and distancing to prevent future intense waves of COVID-19, until herd immunity is reached. However, they suggest cities with low populations and effective vaccination could fully interrupt transmission without the need for physical distancing. In all cities, full 'stay-at-home' lockdowns would no longer be necessary.

The team's results also suggest strong physical distancing interventions implemented for short periods of time may be more effective than mild, longer term ones.

The author and spatial epidemiologist, Dr Shengjie Lai, Senior Research Fellow in Geography and Environmental Sciences at the University of Southampton comments: "Our research provides a framework and set of outputs that can be used by policy-makers and public health authorities to identify appropriate levels of intervention to keep COVID-19 outbreaks in check over time. Although our study was based on data from China, our methods and findings are applicable to cities worldwide with similar levels of population density and social contact patterns."

Director of WorldPop, Professor Andy Tatem, added: "Previous studies have assumed that when people reduce mobility, they proportionately reduce their social contacts, but this isn't necessarily the case and as more SARS-CoV-2 vaccines come online, there is an urgent need to understand the relationship between these factors, so we can adjust and tailor interventions and open up sections of society in a safer way."

The researchers recognize some limitations to their study, for example, the absence of data on the contribution of handwashing and face masks and challenges of vaccine supply, but emphasize that their approach can be quickly adapted to provide near real-time data to address emerging, time critical needs.