Effectiveness of public health measures in reducing COVID-19 incidence

By Jocelyn Solis-MoreiraReviewed by Danielle Ellis, B.Sc.Nov 23 2021

A new review in the BMJ suggests public health measures such as mask-wearing, universal lockdowns, and temporary shutdowns of businesses and schools helped prevent further severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission. Universal lockdowns and mandatory quarantine measures were connected to a decrease in coronavirus disease 2019 (COVID-19) cases and deaths than those countries that did not implement these orders.

Study: Effectiveness of public health measures in reducing the incidence of covid-19, SARS-CoV-2 transmission, and covid-19 mortality: systematic review and meta-analysis. Image Credit: emojoez/ Shutterstock

It is likely that further control of the COVID-19 pandemic depends not only on high vaccination coverage and its effectiveness but also on ongoing adherence to effective and sustainable public health measures,” wrote the research team.

The study

The researchers reviewed the evidence of several public health measures in reducing SARS-CoV-2 transmission and COVID-19 deaths. They included observational and interventional studies that looked at how effective certain public health measures (mask-wearing, handwashing, and social distancing) were in decreasing the risk of COVID-19 infection and death.

A total of 72 studies met eligibility standards, and 35 were included in the final analysis because they measured outcomes of individual interventions. These studies were conducted worldwide, including but not limited to Asia, the United States (U.S.), Europe, and the Middle East.

There was a risk of bias in several studies. Most had major confounding variables, likely because the pandemic was a novel and extenuating circumstance. There were differences in testing capacity, diagnostic criteria, and reporting data on COVID-19 cases and deaths. The risk of bias was most prominent in studies evaluating public health interventions early in the pandemic and in low-income neighborhoods.

PPE measures and COVID-19 risk

Three studies looked at handwashing in people, with an overall 292 people infected with COVID-19 infection. Pooling the results together, handwashing brought an approximate 53% reduction in COVID-19 cases.

Six studies evaluating mask-wearing also showed a 53% decrease in COVID-19 risk. A separate analysis found mask-wearing reduced both SARS-CoV-2 transmission and COVID-19-related mortality rates. For example, one U.S. study showed a 29% reduction in SARS-CoV-2 transmission in states with mask mandates. However, the researchers did not specify the type of masks worn by participants that were protective against infection.

Disinfecting the household and COVID-19 risk

Only one of the 35 studies measured the effectiveness of disinfecting surfaces and SARS-CoV-2 transmission in households.

Daily use of chlorine or ethanol-based disinfectant was 77% effective at lowering the spread of SARS-CoV-2. However, the study was considered to have moderate bias, and the study authors did not collect the concentration of disinfectants used by participants.

Social distancing and COVID-19 risk

Results were based on five studies measuring the usefulness of physical distancing in lowering COVID-19 risk. Pooled results showed a 25% decreased risk of contracting COVID-19 infection. However, all studies had different measurement points and ranged from moderate to critical bias in the data collection.

Stay-at-home efforts and COVID-19 risk

All studies measuring stay-at-home efforts for risk of SARS-CoV-2 showed reductions in viral transmission. In one study from the United Kingdom, there was a 74% decrease in daily number of contacts.

Quarantine efforts were measured in two studies: one from Saudi Arabia and another from India. In Saudi Arabia, an 8-week mandatory quarantine measure brought a 4.9% decrease in COVID-19 infections. A 14-time higher risk of SARS-CoV-2 transmission was observed in Indian regions with no quarantine orders versus those with strict quarantine measures.

Countries that enacted universal lockdowns reported fewer COVID-19 cases than those that did not. One U.S. study looking at universal lockdowns in the first few months of the pandemic showed an 11% reduction in SARS-CoV-2 transmission. In addition, universal lockdowns decreased the number of COVID-19 deaths.

Effect of school and business closings in relation to COVID-19 risk

Two studies looked at the effectiveness of school closures on COVID-19 infection and mortality risk. One U.S. study found that closing schools resulted in a 62% decrease in COVID-19 infections and a 58% decrease in COVID-19 deaths. Conversely, Japan’s school closing did not affect SARS-CoV-2 transmission.

Temporarily shutting down businesses across the United States resulted in a significant 12% reduction in SARS-CoV-2 transmission. A separate U.S. study found a 16% decreased risk in transmission.

Travel restrictions did not alter SARS-CoV-2 risk

One study evaluated travel restrictions in nine African countries that closed their borders in response to the pandemic. There was an increase in COVID-19 cases after closing the border. Border closure did not affect COVID-19 cases. However, it is important to note that the study had a moderate bias risk. Screening incoming travelers did not reduce COVID-19 transmissions. One study found that when screening for fever, about 86% of infected people remained undetected.