Closing public transport had no additional impact, study found, with other measures in place

Closing schools and workplaces and restricting mass gathering significantly slowed the spread of Covid-19 in the early months of the pandemic, according to a pooled analysis of physical distancing data from 149 countries.

Implementation of any one of five tracked physical distancing measures was associated with an average overall reduction in Covid-19 incidence of 13% in the analysis, published July 15 in BMJ.

Four measures – school closures, workplace closures, restrictions on mass gatherings and lockdowns – were found to be responsible for the observed reductions, while closing public transportation was not found to have an additional impact when the other distancing measures were in place.

Countless modeling studies have evaluated the impact of social distancing on SARS-CoV-2 spread, but the newly published study is among the first to use real-world data to examine the effectiveness of physical distancing measures.

Researcher Nazrul Islam, PhD, of the University of Oxford, UK, and colleagues, evaluated data on policy interventions for physical distancing compiled by Oxford’s Covid-19 Government Response Tracker, which collects data on Covid-19 physical distancing practices adopted by governments around the world.

Data on daily reported cases of the virus were compiled by the European Center for Disease Prevention and Control.

The study included all countries or regions that implemented at least one of the 5 physical distancing interventions in the early months of the Covid-19 outbreak, between early January and late May of this year.

On average, physical distancing measures were first implemented 9 days after the first reported case, but some countries had much longer intervals between their first case and putting physical distancing policies in place: Thailand (58 days), Australia (51 days), Canada (46 ays), Sri Lanka and the UK (45 days), and Cambodia, Sweden and the US (40 days).

In an editorial, Thomas May, PhD, of Washington State University’s College of Medicine, wrote that the reliance on actual data instead of hypothetical modeling was both the greatest strength and weakness of the study by Islam and colleagues.

May wrote that “a lack of coordination and standardization in both testing and reporting” from country to country greatly compromised the interpretation of the findings.

In an interview with BreakingMED, May said in the United States, particularly, the politicization of testing and other aspects of Covid-19 response has undermined the ability to deliver clear, unbiased, public health messages.

“The [Islam et al] paper provides useful information, but we could do so much better if we got politics out of these realms,” he said.

May cited as an example the news earlier this week that the Trump administration has directed the nation’s hospitals to bypass the Centers for Disease Control and Prevention (CDC) and send Covid-19 patient information to Health and Human Services (HHS).

“Taking data collection out of the hands of the CDC for potentially political reasons is exactly what we should not be doing,” he said.

“I don’t claim to know why the CDC is being bypassed. But you just have to read the news to know that a lot of people suspect that it is being done to gain political control over the data, and I think that suspicion in itself is a problem,” he added.

In their study, Islam and colleagues utilized interrupted time series analysis, with results synthesized using meta-analysis, to estimate the impact of the 5 social distancing measures (school closure, workplace closure, mass gathering restrictions, lockdowns and public transportation closures) on Covid-19 transmission rates between January 1 and May 30 of this year.

Among their main findings:

  • Implementation of any physical distancing intervention was associated with an average overall reduction in Covid-19 incidence of 13% (IRR 0.87, 95% confidence interval [CI], 0.85-0.89; all 149 countries).
  • Closure of public transport was not associated with any additional reduction in Covid-19 incidence when the other four physical distancing interventions were in place (pooled IRR with and without public transport closure was 0.85; 95% CI, 0.82-0.88; 72 countries and 0.87; 95% CI, 0.84-0.91; 32 countries, respectively).
  • Data from 11 countries also suggested similar overall effectiveness (pooled IRR 0.85, 0.81-0.89) when school closures, workplace closures, and restrictions on mass gatherings were in place.
  • Earlier implementation of lockdown was associated with a larger reduction in Covid-19 incidence (pooled IRR 0.86, 0.84-0.89; 105 countries) compared with a delayed implementation of lockdown after other physical distancing interventions were in place (pooled IRR 0.90, 0.87-0.94; 41 countries).

The researchers acknowledged significant limitations in data collection and other variables which limited the ability to interpret their findings.

“Despite a range of limitations in our study, the findings suggest beneficial effects of physical distancing interventions in combination, especially restrictions on mass gatherings along with school and workplace closures, allowing the maintenance of active public transport for people working in the key service sectors,” they wrote “Our finding of no additional benefit associated with public transport closure when other interventions are in place is likely a result of fewer people using public transport, making it more convenient to maintain physical distancing during essential travel.”

They called for further research “to provide more definitive answers to remaining questions about the extent, intensity, combinations and sequence of physical distancing interventions, as well as the need for additional interventions in the short, medium and long term.”

May agreed that rigorous, scientific studies are needed, along with measured interpretation of future findings.

“We run the risk of undermining public trust if we don’t remember as scientists that there are limitations to the conclusions that can be drawn,” he said.

  1. Closing schools and workplaces and restrictions on mass gathering significantly slowed the spread of Covid-19 in the early months of the pandemic, according to physical distancing data from 149 countries.
  2. Closing public transportation was not found to have an additional impact when the other distancing measures were in place.

Salynn Boyles, Contributing Writer, BreakingMED™

The researchers declared no funding source nor relevant competing interests related to this study. Editorial writer Thomas May also declared no relevant competing interests.


Cat ID: 190

Topic ID: 79,190,254,930,570,730,933,190,926,192,927,151,928,925,934