Anti-contagion interventions prevented up to 62 million confirmed cases of COVID-19
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Anti-contagion policies have prevented or delayed as many as 62 million confirmed COVID-19 infections, which corresponded with the prevention of an estimated 530 million cases in six countries, according to a study published in Nature.
“We found that in the absence of policy intervention, the number of COVID-19 infections doubled approximately every 2 days,” Esther Rolf, a PhD candidate in the computer science department at University of California, Berkeley, told Healio. “In all six countries we studied, we found that the anti-contagion policies put in place significantly slowed the spread of the disease, resulting in an estimated 500 million infections prevented or delayed, across the six countries in the time frame that we studied.”
Rolf and colleagues examined data on 1,717 local, regional and national non-pharmaceutical interventions intended to slow the rate of new COVID-19 infections in the U.S., China, Italy, South Korea, Iran and France. They used reduced-form econometric analysis methods to measure the impact of anti-contagion policies on COVID-19 infection growth rates.
The researchers found that, without interventions, early COVID-19 infection rates would grow at a rate of 43% per day in the six countries, which implied a doubling time of approximately 2 days. Estimates specific to each country ranged from 34% per day in the U.S. to 68% per day in Iran. Results showed intervention measures prevented an estimated 37 million additional confirmed cases of COVID-19, corresponding to an estimated 285 more million infections in China, 38 million more infections in South Korea, 49 million more infections in Italy, 54 million more infections in Iran, 60 million more infections in the U.S. and 45 million more infections in France. Those projections included confirmed cases, according to the study results.
“Since we estimated that millions more infections would have occurred if no policies had been deployed, we did not estimate health outcomes of infected people, as the health care system would likely be overloaded in such a scenario,” Rolf said.
She also noted that the researchers were surprised by the high baseline growth rate of infections.
“The effectiveness of individual policies differs from country to country, but consistently across countries, the aggregate effect of the enacted policies is a significant slowdown of the spread of the virus,” Rolf said. “There are several simulation-based epidemiological models that are currently being used to understand the spread of the disease. These types of models are very useful for projecting what might happen in the future under different conditions. Our methodology is designed to look backward at the policies and infections that occurred, to analyze what has actually happened as the pandemic has unfolded and as policies were implemented in response.”
One of the study’s limitations was the amount of data available during the time periods that the researchers examined.
“We hope our study highlights the value of standardized and rigorous data collection going forward, so that we as a community can understand the effectiveness of different policies and make decisions based on the best possible information and analysis,” Rolf said.
Perspective
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Amesh A. Adalja, MD
It’s not a question of whether or not enforced social distancing decreased cases, averted hospitalizations and reduced deaths. The virus requires social interaction for transmission; anything that decreases social interaction will decrease the opportunity for the virus to spread. To me, the question is how much social distancing needs to be enforced vs. voluntary, what activities were most impactful for viral spread and where these actions were required. It is also important to realize that models are focused solely on COVID-19 and not necessarily looking at the extraneous variables such as delayed chemotherapy, delayed cancer screening, delayed care for routine medical matters, decreased vaccination rates and unemployment. To me, enforced social distancing was really about preserving hospital capacity, and once hospital capacity is assured, social distancing becomes more of an individual decision based on individual risk tolerance and individual values.
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