Thursday, October 6, 2022

COVID restrictions – Moderation is good

In efforts to reduce the spread of COVID-19, billions of people around the world were subject to rules and laws governing their behavior. Among the various non-pharmaceutical interventions (NPIs), what worked? 


An influential early report analyzing data from 11 European countries during the first 4 months of the pandemic found that lockdowns reduced transmission rates (Rt values) significantly, ~80%, whereas other NPIs such as cancelling public events, school closure, encouraging social distancing, and self-isolation, resulted in less significant reductions (0-20%) (Fig 2, Flaxman).  The dramatic drop in infections after lockdown is so obvious that it required no modeling (Fig 1).  A similar study found the most effective NPIs for lowering cases were travel restrictions, school closures, and the partial lockdown (Cortis).  A related study of 19 NPIs during seasonal flu found that banning large gatherings was most effective in limiting transmission (Qiu).  These studies used epidemiological models that directly involve underlying mechanisms.


Data on cases, deaths, vaccinations, and tests, were obtained from the COVID-19 Data Hub (Guidotti).  NPI data were obtained from the Oxford Covid-19 Government Response Tracker (OxCGRT).  


In this report, the author analyzed data from 132 countries between Feb 2020 to April 2021, capturing 3 waves of infection, beginning March 202, July 2020, and January 2021.  An econometric model with 4 equations: C = cases growth rate, D= deaths growth rate, M = mobility, and p(SI) = probability of the assigned stringency intensity level was employed.  Stringency correlates inversely with nonresidential mobility (Fig 3).  He found that ‘unobserved variables’ influence the growth of cases and deaths (C and D) as well as the stringency (SI) of government policies. Medium-stringency measures greatly reduced case and death growth rates but, surprisingly, yet-more-stringent measures slightly increased them (Fig. 4, shown).   

Fig. 4 Case (panel a) and Death (panel b) growth rates vs NPI Stringency Index. 

Testing helped but contact tracing did little (Fig 5).  The benefits of reduced nonresidential mobility were outweighed by increased within-household transmission.  Various differences in culture, compliance, and enforcement of government imposed NPIs were acknowledged but not clearly managed. Even low levels of vaccination reduced Case and Death growth rates with nonlinear improvement anticipated. 

The findings disagree with previous reports that lockdowns are effective, concluding that "very stringent NPIs provide no further benefits over moderately stringent ones, and that less stringent NPIs function primarily as signals for significant voluntary changes in citizens’ behavior.". Such analyses are crucial for designing effective, results-driven policies and for persuading people to comply.  


Spiliopoulos L. On the effectiveness of COVID-19 restrictions and lockdowns: Pan metron ariston. BMC Public Health. 2022 Oct 1;22(1):1842. doi: 10.1186/s12889-022-14177-7. PMID: 36183075; PMCID: PMC9526209.

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