Combined Vaccination, Physical Distancing Can Replace Lockdowns to Prevent COVID-19 Surges

Rather than relying on stay-at-home restrictions to reduce the risk of future peaks in COVID-19 infections, a recent study found that a combination of robust vaccination programs and strict physical distancing rules may be effective in the prevention of infection surges.

During the study, researchers at the University of Southampton, in collaboration with the Chinese University of Hong Kong, used anonymized mobile phone geolocation data with epidemiological and COVID-19 case data from China to create models that would show the potential impact of vaccination programs and physical distancing rules on transmission of the virus.

The researchers used these models to predict the effect each combination of interventions would have on low-, medium-, and high-density cities in China. The researchers noted that density was an important component to consider, as the impact of physical distancing measures on the spread of the virus is dependent on not only the intensity of the measures put in place, but also the population density of the area and the availability of vaccines in that area.

In order to understand the relationship between these different factors more clearly, the team started by predicting that in most cities, vaccination programs and physical distancing combined would be enough to contain virus resurgence without the need to place greater restrictions on the population’s mobility. Containment of the virus resurgence was also defined as the maintenance of a low transmission rate, or 'R' below one.

Based on these factors, the models demonstrated that cities with medium- and high-density populations would need both vaccination and physical distancing implemented to prevent future COVID-19 infection surges of greater intensity, until the point when herd immunity is reached in the population.

On the other hand, the researchers found that for cities with low-density populations, effective vaccination programs would be able to fully interrupt transmission of the virus without the need for additional physical distancing measures.

The researchers specifically noted that for all cities, if these measures were put into place based on the population density of the area, full stay-at-home lockdowns would no longer be necessary.

Additionally, the findings of the study suggest that strong physical distancing interventions implemented for shorter periods of time may have greater efficacy than mild, longer term implementations of physical distancing measures.

"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,” said study author and spatial epidemiologist, Shengjie Lai, senior research fellow in geography and environmental sciences at the University of Southampton, in a press release. “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."

Andy Tatem, PhD, the director of WorldPop at the University of Southampton, also explained the relevance of these findings in relation to current policy measures implemented to prevent future COVID-19 outbreaks.

"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," Tatem said in the press release.

The researchers also noted that there were limitations to their study, such as the absence of data around the impact of handwashing and face masks, and challenges related to vaccine supply. However, they also emphasized that the approaches they present based on their findings can be quickly adapted to provide near real-time data to address emerging, time critical needs.

REFERENCE

Combined vaccination and physical distancing enough to prevent future COVID-19 surges. Southampton, UK: University of Southampton; February 19, 2021. https://www.eurekalert.org/pub_releases/2021-02/uos-cva021921.php. Accessed February 23, 2021.