Frequent rapid antigen tests can help keep

Among oil rig workers, ship crews and other groups of people who work closely together, COVID-19 can spread like wildfire. Yet trying to prevent the spread with long quarantines can be just as disruptive.

In a new study, Yale epidemiologists have found a more practical strategy for COVID surveillance from businesses, teams, schools and communities.

With frequent and regular rapid antigen (RA) testing, as well as the isolation of people who test positive, organizations can effectively reduce the risk of runaway COVID outbreaks and make long quarantines a thing of the past. according to the researchers.

This is possible even if the RA tests are less accurate than the reference PCR tests. The reason? AR tests provide quick results, making up for in speed what they lack in accuracy. This gives them an advantage when frequently used to test groups of people.

“Lately we’ve been raising our hands a lot and asking, ‘What can we do? People think there is no way to eliminate risk. But that’s not true,” said lead author Jeffrey Townsend, Elihu Professor of Biostatistics at the Yale School of Public Health and Professor of Ecology and Evolutionary Biology at Yale University. “If you test frequently enough, you can suppress transmission within a community.”

The study appears online in Communication Medicine.

In an October 2021 study that changed US Centers for Disease Control and Prevention (CDC) policy, Townsend’s team demonstrated that 14-day quarantines can be safely shortened to seven days if people test negative with a PCR test on the seventh day.

The current study suggests a way for groups to shorten quarantine even further.

Rapid antigen tests may offer a way forward

For the study, the researchers used public data and mathematical models to investigate three questions:

  • After a person leaves quarantine with a negative PR test, what is the likelihood that they will transmit COVID to others?
  • If they transmit COVID, how many people are likely to be infected?
  • How do 18 commercially available, FDA-cleared RA tests compare to PCR tests in terms of accuracy?

Taking into account the variations of different commercially available RA tests, the authors found that the ability of these tests to reduce post-quarantine transmission depends on (1) the length of quarantine and (2) the speed with which which the results return. The timing of RA tests in relation to a person’s infection status – before, during or after symptoms appear – is also important.

Speed ​​is key. Although less accurate than the PCR test, the RA test gives results in minutes, while a PCR test can take several hours or even days, hampering real-time detection of who is infectious. After all, people can contract or transmit COVID while waiting for results.

When testing to exit a quarantine of two days or less, the authors found that a rapid-running negative RA test can reduce COVID transmission more effectively than a 24-hour-running PCR test.

“It turns out that rapid antigen testing is basically as good as PCR if there’s a day’s delay in getting your PCR results,” Townsend said. “Warning people they are sick is essential for them to prevent further transmission.”

How often should testing take place?

With testing every other day, all brands of AR testing — even the least accurate — work to suppress COVID outbreaks, the authors found.

“Any transmission will likely die out very quickly,” Townsend said.

Testing every three days was achievable with some AR tests, while others weren’t precise enough to offer a clear picture.

However, testing every four or five days risked spreading COVID out of control.

With masking, ventilation, vaccines and other related measures in place, the protection that frequent testing can provide is even stronger, Townsend said.

“If you do these regular tests for sports teams and other people who work closely together, you can give them confidence that they can be part of this group,” he said. “It does not mean that no one will get COVID-19. But that means there won’t be those extended transmissions within groups. Thus, people may feel some sense of assurance that their group, at least, is at relatively low risk.

The study was funded by the Notsew Orm Sands Foundation, BHP and BP.

The study’s first author was Chad R. Wells, a postdoctoral fellow at the Center for Infectious Disease Modeling and Analysis (CIDMA) at the Yale School of Public Health. The co-authors were research scientist Abhishek Pandey and Professor Alison P. Galvani, also from CIDMA; Seyed M Moghadas of York University in Toronto; Burton H. Singer of the University of Colorado Anschutz Medical Campus; Gary Krieger of NewFields E&E in Boulder and the University of Colorado Anschutz Medical Campus; Richard JL Heron and David E. Turner, both of BP; Justin P. Abshire and Kimberly M. Phillips, both of BHP Petroleum; and A. Michael Donoghue of BHP Group. Dr. Townsend also holds positions in the Computational Biology and Bioinformatics program and the Microbiology program, both at Yale University.


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