An exciting new study by researchers at the Universities of Oxford and Edinburgh and published on the preprint server medRxiv* in July 2020 reports that early and stringent government measures in the form of non-pharmaceutical interventions (NPIs) against the spread of COVID-19 results in a significant reduction in the mortality due to this disease. The finding could help shape public health policies in the absence of effective vaccines or therapeutic drugs.
NPIs and COVID-19 Control
The ongoing COVID-19 pandemic is now bringing a second and larger wave of infection in the U.S., having already infected nearly 3 million individuals there. Attempts to control the spread of SARS-CoV-2 in the U.S. have relied exclusively on NPIs, such as school closures, physical distancing in places outside the home, lockdowns on travel, and prohibitions on public gatherings.
The aim of these NPIs is to act along with contact tracing and testing to create physical space barriers across which the virus will not spread quickly. Other countries resorted to extreme lockdowns, bringing economic and social activity to an almost complete halt. The costs of such policies in terms of the financial and health implications are still being calculated.
Pioneering Study: Stringency Index and COVID-19 Deaths
The current study aims to analyze the government responses to the threat globally and offers a pioneering evaluation of how this is related to viral spread in many different countries. The researchers built up the most comprehensive database known so far in this area, tracking the responses of 170 governments day by day over the period January 1, 2020, to May 27, 2020, across time and countries.
The researchers wanted to assess whether the speed and rigor of governmental NPIs would reduce the growth and mortality due to COVID-19 in the country concerned. This would provide firm data on how these steps actually impact the outcome is still lacking.
This observational study included both containment and closure policies, combining data on nine NPIs such as restrictions on international and domestic travel, public information drives, contact tracing, and testing, and bans on public gatherings to form a new measure called the stringency index (S.I.). This was scored as an aggregate measure for each country for each day.
The rationale was that most of the countries in the study applied NPIs as a package of measures, besides the obvious simplicity and ease of this measure, and the ability to compare the stringency and outcome of these interventions across a time frame and a range of countries.
Speed of Government Response and Peak Deaths
The researchers adjusted for the effect of time and country-specific factors, including the demographic constitution, the health system, and the economic characteristics of the country. They related these to the outcome, namely, deaths due to COVID-19, using two measures – maximum daily deaths and growth rate for daily deaths. A time lag was introduced to relate the stringency applied six weeks before to outcome changes at the current time. This would hopefully mitigate the effect of time on the natural course of the disease as well as minimize the possibility of reverse causation.
Faster and Stronger Response Reduces Cumulative Mortality
The study showed that first, the maximum number of daily deaths was related to a delay of days in introducing the first response. Again, each day of delay in applying measures to reach an SI of 40 caused the average daily growth rate for deaths to rise by 9 percent.
Thus, if one country applied NPIs with an SI of 40 a month later than another, it would incur an average growth rate in COVID-19 mortality that was 2.5 percentage points higher. This translates into significant increases in total mortality over time.
Speed of Government Response and Growth in New Deaths
Also, as the S.I. rose by one point, the average daily growth rate for deaths fell by 0.080 percentage points. These daily differences in growth rates mounted up to cause significant impacts. When the given country applied less stringent measures, the mortality rose. For instance, when policies that would lead to an SI of 40 were delayed for a week, the cumulative mortality would be 1.7 times as high as otherwise.
The study also compares six countries by way of illustration, showing that the U.S., with its slow and weak stringency index, has the highest mortality and the slowest control. In contrast, Botswana, with a quick and firm response, has had almost zero mortality maintained over time. The African nation of 2.25 million people has to date had a total of 314 cases and a single death. South Korea closely follows this. With a total population of approximately 51.6 million, the country has seen 13,244 cases and 285 deaths.
Degree of Government Response and Growth in Deaths
More research will be needed to assess the role of national as well as individual policies, in various permutations.
The study concludes, “A lower degree of government stringency and slower response times were associated with more deaths from COVID-19. These findings highlight the importance of non-pharmaceutical responses to COVID-19 as more robust testing, treatment, and vaccination measures are developed.”
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.