Jabs Alone Won’t Do the Job: Physical Distancing Still Needed to Fight COVID-19
CUHK investigates the effect of vaccination on preventing COVID-19 resurgence.
With COVID-19 vaccination programmes now being rolled out across the globe, many urban dwellers are eagerly anticipating the end of physical distancing measures. However, a new epidemiological study from CUHK with participation from the University of Southampton in the UK has found that physical distancing measures should be maintained in cities until herd immunity is achieved. The research results have been published in the journal Nature Human Behaviour.
COVID-19 cases have surged worldwide since the summer of 2020, after many countries relaxed lockdown and physical distancing measures in the course of reopening. Hope is now being placed in vaccination as a route out of such restrictions, but it remains unclear how well vaccines will be able to deliver on this promise, especially given that vaccine supply is unlikely to be sufficient to achieve herd immunity in the immediate future.
This prompted a multi-disciplinary team of CUHK researchers, including microbiologists, sociologists, geographers and management scholars, to assess the joint effects of vaccination and physical distancing in preventing COVID-19 resurgence. The results show that when effective vaccines are administered, physical distancing measures in cities can be relaxed to varying degrees until herd immunity is achieved but should be maintained to some degree until that point. The research also strongly recommends that cities with high population densities should commence vaccination programmes as soon as possible, as it will be more costly for them to stem future resurgences.
Vaccination programmes should be combined with physical distancing to prevent COVID-19 resurgence.
Modelling Complex COVID-19 Landscape
In order to control the various interrelated factors influencing COVID-19 case rates, such as reopening, stay-at-home orders, physical distancing, the closure of non-essential facilities, vaccination programmes and population density, researchers devised a social contact index (SCI) based on anonymised mobile geolocation data from Wuhan, captured between the city’s pre-lockdown and post-lockdown periods in early 2020. This model allowed the research team to quantify the impact of both physical distancing and vaccination measures in a unified way, bridging the gaps between intervention measures and disease transmission. A generalised approach for other cities with varying population densities was then developed.
Several combinations of interventions were assessed using the SCI model. It was found that, compared with a no-vaccination scenario, vaccination programmes combined with physical distancing can contain virus resurgence without relying on mobility reduction, whereas a gradual vaccination process alone cannot achieve this. So it is important to take both actions in order to combat COVID-19.