The recent surge of COVID-19 cases is strengthening the case for more frequent testing.

Why it matters: The more contagious Delta variant threatens the fuller reopening of offices and schools in the fall. But regular testing — especially with cheap and almost instantaneous tests — could help catch cases before they have a chance to spread.

Driving the news: President Biden reportedly plans to announce today that all civilian federal employees will need to be vaccinated, or submit to regular COVID-19 testing and adhere to other social distancing requirements.

• It's the latest sign that regular testing could emerge as a potential fallback for workplaces trying to reopen without full vaccination coverage.
• In New York, Citigroup is requiring unvaccinated employees to use an at-home rapid test three times a week, and wear masks in the office, while Goldman Sachs has begun regular testing for unvaccinated workers.
• In Delaware, health and education officials are working with the diagnostic company Quidel to bring rapid testing to the state's 350 schools for unvaccinated staff and students.

By the numbers: From a peak of more than 2.3 million COVID-19 tests a day in early January 2021, daily testing fell to fewer than 900,000 a day by mid-July.

• But testing numbers have risen somewhat in recent days, with pharmacies in high-spread states like Florida reporting a sharper increase.
• "The past 10 days have been going off the hook," says Barry Abraham, the president and COO of Empowered Diagnostics, a south Florida-based company that provides corporate COVID-19 testing. "The testing centers are going back to December numbers."

What they're saying: "The most important aspect of these tests is the rapid result," Michael Mina, an epidemiologist at the Harvard T.H. Chan School of Public Health, told the New York Times last month.

• "Waiting two to three days for laboratory test results isn’t ideal when you need results quickly to make decisions about going to school, work or a social gathering," he said.

Between the lines: Germany, which got off to a much slower start vaccinating its population than the U.S., has managed to largely control its COVID-19 outbreak by making frequent rapid testing a requirement for almost any kind of indoor social activity.

• A recent study in the U.K. found that daily testing and contact tracing — even without isolation — kept students in school without increasing the virus' spread.

The other side: Some researchers worry that regular testing of the vaccinated would turn up cases that don't carry symptoms and aren't likely to spread, potentially leading to unnecessary disruption.

• Yes, but: On Tuesday the CDC changed part of its guidance, advising that vaccinated people should be tested if they come into close contact with a confirmed COVID-19 case.
• The fact that vaccinated people apparently can transmit the virus if they experience a breakthrough case supports the idea that more regular testing could be useful, especially if vaccine efficacy declines over time.

Be smart: Far and away the most effective way to reduce spread is to increase vaccine coverage. Even with breakthrough cases, the Delta surge is primarily a "pandemic of the unvaccinated," as CDC head Rochelle Walensky said last week.

• But with school and office reopenings potentially on the line, both policymakers and executives should keep in mind they're fighting a two-front war: encouraging the unvaxxed to get a shot, but also reassuring the vaccinated that a full return to public life is safe.
• Testing is one way to achieve the latter.