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For immediate release: November 20, 2020
Boston, MA – Testing half the population each week with inexpensive, high-turnover COVID-19 tests would drive the virus to elimination within weeks, even though these tests are significantly less sensitive than benchmark clinical tests, according to a new study released today by researchers at Harvard TH Chan School of Public Health and the University of Colorado at Boulder.
Such a strategy could lead to “personalized home orders” without closing restaurants, bars, retail stores and schools, the authors said.
“Our general observation is that in public health, it is better to have a less sensitive test with results today than a more sensitive test with results tomorrow,” said lead author Daniel Larremore, assistant professor computer science at UC. Rock. “Rather than telling everyone to stay home to make sure someone who is sick doesn’t pass it on, we could give orders to stay home only to people with contagion so that everyone can live their lives. . “
For the study, which was published online November 20, 2020 in Science Advances, Larremore partnered with collaborators from UC’s BioFrontiers Institute and Harvard Chan School to explore whether sensitivity, frequency, or Test turnaround times are the most important in curbing the spread of COVID-19.
Researchers scanned the available literature on how the viral load rises and falls inside the body during infection, when people tend to have symptoms, and when they become contagious.
They then used mathematical modeling to predict the impact of screening with different types of tests on three hypothetical scenarios: in 10,000 individuals; in a university-type setting of 20,000 people; and in a city of 8.4 million people.
When it comes to reducing propagation, they found that frequency and turnaround time are much more important than sensitivity of tests.
For example, in a scenario in a big city, widespread testing twice a week with a rapid but less sensitive test reduced the degree of infectivity, or R0 (“R nothing”), of the virus by 80%. But twice-weekly testing with a more sensitive PCR (polymerase chain reaction) test, which takes up to 48 hours to return results, reduced infectivity by just 58%. In other scenarios, when the amount of tests was the same, the rapid test still reduced infectivity better than the slower, more sensitive PCR test.
Indeed, about two-thirds of those infected have no symptoms and, while awaiting their results, they continue to spread the virus.
“This article is one of the first to show that we should care less about the sensitivity of tests and, in public health, prioritize frequency and time to completion,” said the co-author. Principal Roy Parker, Director of the BioFrontiers Institute and Howard Hughes Medical. Researcher of the Institute.
The study also demonstrates the power of frequent testing to shorten the pandemic and save lives.
In one scenario, in which 4% of people in a city were already infected, rapid testing of three out of four people every three days reduced the number ultimately infected by 88% and was “enough to drive the epidemic to extinction in. every six weeks ”.
The study comes as companies and university research centers are developing rapid, low-cost tests that could be deployed in large public spaces or marketed for DIY use.
Levels of sensitivity vary widely. Antigen tests require a relatively high viral load – about 1,000 times more virus than PCR test – to detect infection. Another test, known as the RT (Reverse Transcription Loop Mediated Isothermal Amplification) lamp, can detect virus about 100 times more virus compared to PCR. The standard PCR test typically provided by healthcare professionals requires as few as 5,000 to 10,000 copies of viral RNA per milliliter of sample, which means it can catch the virus very early or very late.
In the past, federal regulators and the public have been reluctant to adopt rapid tests for fear of missing cases early in the infection. But, in reality, an infected person can go from 5,000 particles to 1 million copies of viral RNA in 18 to 24 hours, Parker said.
“There is a very short window, at the onset of infection, in which PCR will detect the virus, but something like an antigen or a LAMP test won’t,” Parker said.
And during that time, the person is often not contagious, he said. The authors recently used these results to call for a change in the way we think about test sensitivity in the New England Journal of Medicine.
“These rapid tests are contagiousness tests,” said co-lead author Michael Mina, assistant professor of epidemiology and faculty member at the Center for Communicable Disease Dynamics at Harvard Chan School. “They are extremely effective at detecting COVID-19 when people are contagious.”
They are also affordable, he added. Rapid tests can cost as little as $ 1 each and return results in 15 minutes. Some PCR tests can take several days.
Mina envisions a day when the government sends simple, inexpensive DIY tests to every home in the United States. Even if half of Americans tested themselves weekly and self-isolate if they tested positive, the result would be profound, he said.
“In a matter of weeks, we could see this outbreak go from a huge number of cases to very manageable levels,” Mina said.
Rapid testing could also be the key to reviving old and widespread threats such as football stadiums, concert halls and airports, with customers testing themselves on the way and still wearing masks as a precaution, Larremore said.
“Less than 0.1% of the current cost of this virus would allow frequent testing for the entire American population for a year,” Mina said, referring to a recent economic analysis released by the National Bureau of Economic Research.
The authors say they are encouraged to see that several countries have already started testing all of their citizens, and hope the new US administration has made rapid testing a priority. The Food and Drug Administration approved the first rapid home test on Tuesday.
“It’s time to change the mindset around testing to think of a COVID test as something you get when you think you’re tired of seeing it as a vital tool for breaking chains of transmission and keeping the economy open. Larremore said.
The other author from Harvard Chan School was James Hay.
This study was supported by the NIH (F32 AI145112, F30 AG063468, MURI W911NF1810208, 1DP5OD028145-01) and Howard Hughes Medical Institute.
“The sensitivity of the tests is secondary to the frequency and processing time for COVID-19 screening”, Daniel B. Larremore, Bryan Wilder, Evan Lester, Soraya Shehata, James M. Burke, James A. Hay, Milind Tambe , Michael J. Mina and Roy Parker, Science Advances, online November 20, 2020, doi: https://doi.org/10.1126/sciadv.abd5393
Photo: Wyss Institute at Harvard University
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Nicole Blowjob
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Harvard TH Chan School of Public Health brings together dedicated experts from many disciplines to educate new generations of global health leaders and generate powerful ideas that improve the lives and health of people everywhere. As a community of leading scientists, teachers and students, we work together to bring innovative ideas from the lab to people’s lives – not only by making scientific breakthroughs, but also by working to change individual behaviors, public policies and health care practices. Each year, more than 400 faculty members at Harvard Chan School teach more than 1,000 full-time students around the world and train thousands more through online and executive training courses. Founded in 1913 as the Harvard-MIT School of Health Officers, the school is recognized as the oldest public health professional training program in the United States.
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