As the COVID-19 pandemic continues to take a huge economic, social, and physical toll on the world, there is considerable uncertainty as to what nonpharmaceutical interventions (NPIs) are most effective. A new study published on the preprint server medRxiv* in July 2020 shows that some less intrusive NPIs are better than total lockdown. This may help to shape future measures should repeated waves of the pandemic occur.
The Issue with NPIs
The start of NPIs was marked by hesitancy and a lack of confidence in many countries, due to the lack of scientific evidence to underpin their efficacy and because of the enormous cost involved. For instance, both the World Health Institute (WHO) and the Robert Koch Institute (RKI) of Germany did an about-turn on their recommendations against masks, admitting that when correctly used, they did reduce the risk of transmission considerably. There was also considerable pushback by the people in the US and possibly elsewhere.
In this new study, the researchers compare the most restrictive measures to “hitting the infection curve with a blunt sledgehammer, hoping that some of the interventions might suppress transmission to the degree that drives the effective reproduction number, Rt, below one.” This is due to the social, economic, and psychological costs of the lockdown.
Time-ordered NPI co-implementation network across countries. Nodes are categories (L2) with color indicating the theme (L1) and size is proportional to the average effectiveness of the intervention. Arrows from nodes i to j represent that countries that have already implemented intervention i tend to implement intervention j later in time. Nodes are positioned vertically according to their average time of implementation (measured relative to the day where the country reached 30 confirmed cases) and horizontally according to their L1 theme.
The Study: Ranking NPIs for Efficacy
Prior research has often focused on a single type of intervention, such as travel restriction, social distancing, or personal protection. The current study uses a broader ranked data set of almost 4,500 NPIs in 76 regions, to find how these impact the reproductive rate of the virus. They used multiple methods to cover both national strategies and certain selected strategies. Finally, they zoomed in on the possible impact of a lockdown and its relevance concerning the timing of intervention.
Using four different measures, they found that the most effective NPIs in terms of reducing the Effective Reproduction Number (Rt) center around social distancing, healthcare capacity, risk communication, and travel restriction. All four methods showed maximum effectiveness with educational institution closure, cancellation of small gatherings, border restrictions and making personal protective equipment available, increased numbers of healthcare workers, communication with other stakeholders, and reducing the burden on the healthcare system.
Most Effective Methods
Three methods agreed in the effectiveness of seven other NPIs, namely, public education and communication, canceling mass gatherings, restricting individual movement, increasing the supply of medical equipment, creating containment zones, and measures protecting special populations.
Typically, countries follow this pattern: cancellation of mass gatherings, cancellation of small gatherings, education and public communication, social distancing, and travel restriction measures. These last two include school and workplace closures, containment zones, movement restrictions at the individual level, and finally, a complete lockdown.
Among these, prohibitions on small gatherings are the most effective but the most costly in terms of daily human interaction. Safety guidelines for the workplace and public transport consistently do little to reduce the Rt, across most countries, according to the studies. This will need further confirmation, of course.
On the other hand, travel restrictions across national borders are highly effective when European countries are included, but insignificant in effect in two methods when these are removed. This could be due to the high degree of variability in restricting movement across borders.
Increasing the use of face masks by healthcare workers is very effective in reducing the Rt, as well as public communication and promoting face mask use. However, their use by the public is not so strongly linked to efficacy. Of course, masks were not always available when first promoted, which could have impacted their effectiveness. Face masks were generally promoted early in the epidemic, about 3 days, on average, after 30 cases were recorded.
Crisis management plans were found to be very effective in all countries except those of the American continents, which shows that these had no effective plans in place. This could be due to the weaker socioeconomic base as well as the weaker central government in many countries in this region.
Self-isolation of the symptomatic was also more effective than quarantining those who were exposed or infected. All these show that voluntary measures are more effective than mandatory measures.
Variable Effectiveness Across Territories
An important finding was that the effectiveness of the NPI is not dependent on the country or state, but varies significantly from region to region. This is a function of socioeconomic features and of already existing NPIs. Thus, NPIs do not work as well in so-called developed countries, those where governments are more accountable, and which are more stable politically.
Finally, the efficacy of a national lockdown was assessed with respect to other measures. The study found that the phase of the epidemic is a vital factor in determining the effectiveness of a lockdown, with the ideal motto being “the earlier, the better.” Recent work shows that the reduction in Rt could be anywhere from 5% to 80%. Even though later lockdowns are less effective, they are still not useless.
Implications for Future Control Measures
In short, the researchers say, “Our findings suggest that there is no silver bullet to efficiently reduce the burden of a potential second COVID-19 wave or any similar future viral respiratory epidemics through NPIs. Instead, we identify several decisive interventions that significantly contribute to reducing Rt below one, though none of these interventions alone would be enough to stop the epidemic.”
Future approaches could concentrate on social distancing, travel restriction, and increasing healthcare and public health capacity by voluntary self-isolation and similar measures. Multiple effective measures must be soldered together optimally to achieve the best containment and enable re-opening sooner.
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.