Two studies look at ways to stay safe while we wait for the vaccines roll-out

Two reports cover masks, bubbles, rapid tests and other measures that work

Edited by Will Collette

By Matt Davies, Newsday

As the world-wide COVID pandemic goes on, scientists around the world are taking hard, critical looks at measures we can all take NOW that can stem the tide now that we have realistic hope for safe and effective vaccines.

I have put together two research articles because they essentially offer the same thing: practical information on ways to stay safe.

As Dr. Tony Fauci keeps saying, we all need to be patient and follow good public health practices that, with every new study, we know to be science-based and sensible.

Please continue for these two timely reports.

Social bubbles and masks more situation-dependent in terms of effectiveness

Simon Fraser University

Summary:

Researchers have found that physical distancing is universally effective at reducing the spread of COVID-19, while social bubbles and masks are more situation-dependent. The researchers developed a model to test the effectiveness of measures such as physical distancing, masks or social bubbles when used in various settings.

Simon Fraser University professors Paul Tupper and Caroline Colijn have found that physical distancing is universally effective at reducing the spread of COVID-19, while social bubbles and masks are more situation-dependent.

The researchers developed a model to test the effectiveness of measures such as physical distancing, masks or social bubbles when used in various settings.

Their paper was published Nov. 19 in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).

They introduce the concept of "event R," which is the expected number of people who become infected with COVID-19 from one individual at an event.

Tupper and Colijn look at factors such as transmission intensity, duration of exposure, the proximity of individuals and degree of mixing -- then examine what methods are most effective at preventing transmission in each circumstance.

The researchers incorporated data from reports of outbreaks at a range of events, such as parties, meals, nightclubs, public transit and restaurants. The researchers say that an individual's chances of becoming infected with COVID-19 depend heavily on the transmission rate and the duration -- the amount of time spent in a particular setting.

Events were categorized as saturating (high transmission probability) or linear (low transmission probability). Examples of high transmission settings include bars, nightclubs and overcrowded workplaces while low transmission settings include public transit with masks, distancing in restaurants and outdoor activities.

The model suggests that physical distancing was effective at reducing COVID-19 transmission in all settings but the effectiveness of social bubbles depends on whether chances of transmission are high or low.

In settings where there is mixing and the probability of transmission is high, such as crowded indoor workplaces, bars and nightclubs and high schools, having strict social bubbles can help reduce the spread of COVID-19.

The researchers found that social bubbles are less effective in low transmission settings or activities where there is mixing, such as engaging in outdoor activities, working in spaced offices or travelling on public transportation wearing masks.

They note that masks and other physical barriers may be less effective in saturating, high transmission settings (parties, choirs, restaurant kitchens, crowded offices, nightclubs and bars) because even if masks halve the transmission rates that may not have much impact on the transmission probability (and so on the number of infections).

The novel coronavirus is relatively new but the science continues to evolve and increase our knowledge of how to effectively treat and prevent this highly contagious virus. There is still much that we do not know and many areas requiring further study.

"It would be great to start collecting information from exposures and outbreaks: the number of attendees, the amount of mixing, the levels of crowding, the noise level and the duration of the event," says Colijn, who holds a Canada Research Chair in Mathematics for Evolution, Infection and Public Health.

Frequent, rapid testing could cripple COVID-19 within weeks, study shows

Research shows test turnaround-time, frequency far more important than sensitivity in curbing spread

University of Colorado at Boulder

Testing half the population weekly with inexpensive, rapid-turnaround COVID-19 tests would drive the virus toward elimination within weeks -- even if those tests are significantly less sensitive than gold-standard clinical tests, according to a new study published today by University of Colorado Boulder and Harvard University researchers.

Such a strategy could lead to "personalized stay-at-home orders" without shutting down restaurants, bars, retail stores and schools, the authors said.

"Our big picture finding is that, when it comes to public health, it's better to have a less sensitive test with results today than a more sensitive one with results tomorrow," said lead author Daniel Larremore, an assistant professor of computer science at CU Boulder. "Rather than telling everyone to stay home so you can be sure that one person who is sick doesn't spread it, we could give only the contagious people stay-at-home orders so everyone else can go about their lives."

For the study, published in the journal Science Advances, Larremore teamed up with collaborators at CU's BioFrontiers Institute and the Harvard T.H. Chan School of Public Health to explore whether test sensitivity, frequency, or turnaround time is most important to curb the spread of COVID-19.

The researchers scoured available literature on how viral load climbs and falls inside the body during infection, when people tend to experience symptoms, and when they become contagious.

They then used mathematical modeling to forecast the impact of screening with different kinds 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.

When it came to curbing spread, they found that frequency and turnaround time are much more important than test sensitivity.

For instance, in one scenario in a large city, widespread twice-weekly testing with a rapid but less sensitive test reduced the degree of infectiousness, or R0 ("R naught"), 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 infectiousness by only 58%. When the amount of testing was the same, the rapid test always reduced infectiousness better than the slower, more sensitive PCR test.

That's because about two-thirds of infected people have no symptoms and as they await their results, they continue to spread the virus.

"This paper is one of the first to show we should worry less about test sensitivity and, when it comes to public health, prioritize frequency and turnaround," said senior co-author Roy Parker, director of the BioFrontiers Institute and a Howard Hughes Medical Institute investigator.

The study also demonstrates the power of frequent testing in shortening the pandemic and saving lives.

In one scenario, in which 4% of individuals in a city were already infected, rapid testing three out of four people every three days reduced the number ultimately infected by 88% and was "sufficient to drive the epidemic toward extinction within six weeks."

The study comes as companies and academic research centers are developing low-cost, rapid turnaround tests that could be deployed in large public settings or commercialized for do-it-yourself use.

Sensitivity levels vary widely. Antigen tests require a relatively high viral load -- about 1,000 times as much virus compared to the PCR test -- to detect an infection. Another test, known as RT-lamp (reverse transcription loop-mediated isothermal amplification), can detect the virus at around 100 times as much virus compared to the PCR. The benchmark PCR test requires as little as 5,000 to 10,000 viral RNA copies per milliliter of sample, meaning it can catch the virus very early or very late.

In the past, federal regulators and the public have been reluctant to embrace rapid tests out of concern that they may miss cases early in infection. But, in reality, an infected person can go from 5,000 particles to 1 million viral RNA copies in 18 to 24 hours, said Parker.

"There is a very short window, early in infection, in which the PCR will detect the virus but something like an antigen or LAMP test won't," Parker said.

And during that time, the person often isn't contagious, he said.

"These rapid tests are contagiousness tests," said senior co-author Dr. Michael Mina, an assistant professor of epidemiology at the Harvard T.H. Chan School of Public Health. "They are extremely effective in detecting COVID-19 when people are contagious."

They are also affordable, he added. The 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, cheap DIY tests to every home. Even if half of Americans tested themselves weekly and self-isolated if positive, the result would be profound, he said.

"Within a few weeks we could see this outbreak going from huge numbers of cases to very manageable levels," Mina said.

Rapid testing could also be the key to breathing life back into former super spreader threats like football stadiums, concert venues and airports, with patrons testing themselves on the way in and still wearing masks as a precautionary measure, Larremore said.

"Less than .1% of the current cost of this virus would enable frequent testing for the whole of the U.S. population for a year," said Mina, referencing a recent Harvard economic analysis.

The authors say they are heartened to see that several countries have already begun testing all of their citizens, and hopeful that the new U.S. administration has named rapid testing as a priority.

"It's time to shift the mentality around testing from thinking of a COVID test as something you get when you think you are sick to thinking of it as a vital tool to break transmission chains and keep the economy open," Larremore said.