Can we safely open schools in the Delta era?

Yes, if we implement rapid antigen testing, a powerful and under-utilized weapon.

A simple phrase from a bygone era: “Don’t worry, I’m not contagious.” Remember when people with colds used to just say that? As a physician, I always wondered, how could they possibly know?

They didn’t. They were guessing. Most common colds are most contagious in the first few days of symptoms, but can spread to a lesser extent for as long as 7 to 14 days. The peak contagious period for seasonal influenza covers the first 3 or 4 days of symptoms, with transmissibility sometimes lasting up to a week. If those saying, “I’m not contagious” were occasionally wrong, the stakes were relatively low.

We can’t roll the dice with SARS-CoV-2, the coronavirus that causes Covid-19. It’s just too dangerous. But I come bearing good news. We can rapid test our way out of this. If we commit to a massive program of rapid testing, we can safely keep schools and many other important aspects of daily life open, even in the Delta era.

Throughout the pandemic rapid antigen tests have been tragically misunderstood. Rapid antigen tests do not generate too many false negative results (that is, negative results even though the person being tested is actually positive). They simply are not designed to identify cases in the pre- and post-contagious periods. Rapid antigen tests reliably indicate whether or not a person is contagious. It may sound jarring, but if someone either just caught coronavirus or is on the tail end of their infection, they pose no threat to others. People who have tested positive for coronavirus can safely go about their normal life provided they are not contagious. That, more than anything, is what matters in controlling a pandemic.

We accept this fact already, if you think about it. It’s exactly what happens after people complete their mandatory isolation or quarantine period after a coronavirus infection or high-risk exposure.

People who have tested positive for coronavirus can safely go about their normal life provided they are not contagious....We accept this fact already, if you think about it.

The recommendations on the duration of isolation and quarantine are based on averages which were derived from population data. The reality is that many people are contagious for less than 10 days, and a select few may be contagious for longer. Asking people to hunker down for too short a period is dangerous for obvious reasons. Asking them to sequester for too long comes with other costs, ranging from days of missed work to pandemic fatigue (i.e. losing steam and ignoring all of the guidelines). The Delta variant adds complexity because it may lengthen the contagious window compared to previous versions of the virus. Vaccines may shorten that window, but apparently not entirely. With a negative rapid test, though, one can truly say “I’m not contagious,” and not be guessing. Think how powerful that information is.

Yes, Delta has changed things. Before Delta, it appeared that vaccinated people did not need routine testing. Breakthrough infections were too rare, and breakthrough contagion rarer still. With Delta, that no longer seems certain. But that doesn’t mean we automatically have to cancel life-as-we-know-it the way we did when the pandemic was declared 18 months ago. Here’s why:

While Delta means that permanent herd immunity has become even more elusive—perhaps impossible—a state of temporary and reliable herd safety can be achieved tomorrow. One recent study showed that rapid antigen testing among hospitalized Covid-19 patients was just as good as super-sensitive PCR tests in detecting contagious individuals, as long as testing was conducted more frequently than every four or five days. Rapid tests are also far cheaper and can be done anywhere, anytime, and do not require a healthcare professional to administer. They are simple to perform and work similar to home pregnancy tests.

While Delta means that permanent herd immunity has become even more elusive—perhaps impossible—a state of temporary and reliable herd safety can be achieved tomorrow.

We can apply this knowledge to schools. Using widescale frequent rapid testing, in-person learning can re-open safely in many places (though especially those with high vaccination rates in the community). Also, in the event of an important outbreak, classrooms or entire schools could be closed within minutes or hours of a contagious case being identified, rather than days later with the PCR test-based regimens used last year, which must be sent to a lab and take far too long. PCR tests can remain positive for weeks, meaning that they might consign a person to isolation who ceased being a threat long ago.

In fact, officials will be able to close schools both sooner and less often than before by using rapid testing protocols; schools would close sooner because rapid tests provide actionable results in just minutes, and they would close less often because the kinds of tests used last year (PCR tests that look for the genetic material of the virus, but don’t distinguish between contagious and non-contagious infections) may have triggered school closures unnecessarily. A combination of frequent rapid antigen tests and intermittent PCR tests might be powerful in some areas. A high frequency rapid testing program will keep schools from closing too late and re-opening either too soon or too late, both of which pose problems.

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Can we afford this? We can’t afford not to. Let’s run the numbers. There are over 8 million employees in the US elementary and secondary school system and around 56 million children. Schools in most states are open 36 weeks per year. At scale, rapid tests cost $5 each. That means we could administer a rapid test to every person in the US school system twice per week for the coming year for around $23 billion. That may sound like a lot until you remember that the last stimulus package was $1.9 trillion. Isn’t keeping schools open safely worth 1.2% of the last stimulus? Not to mention, we’d quickly recover those costs by allowing the economy in these communities to remain open more often. Employed people do not need paycheck support.

Can we afford this? We can’t afford not to.

With at-scale rapid antigen testing regimens in place, we don’t even have to settle the debate over how important schools really are in community outbreaks. Everyone agrees that a child (or adult) who tests positive on a rapid antigen should isolate. Those worried that over-testing could lead to false positives—and therefore unnecessary closures—needn’t worry. Today’s best protocols confirm any positive rapid test with a second test, usually a PCR test. Those still worried that rapid tests can be “falsely negative” need to be reminded: rapid antigen testing almost never yields false negatives; most negative results in infected people are “correctly negative” for contagiousness. That’s why testing protocols, especially in areas with active community spread, must include testing more than once per week to be sufficiently safe. Delaware has taken the lead in implementing and paying for rapid tests to keep schools safe. Other states need to follow suit. Congress should help fund it when needed. The Food and Drug Administration should seek out and authorize more rapid tests to bolster supplies.

Some at the CDC do not like rapid tests, because their results are not automatically reported to public health officials. We can find ways to solve that problem. The CDC needs to remember that its top priority is keeping the public safe, and not epidemiology. While both are important projects (and my own research hinges on large and reliable datasets), we should all agree that saving lives and limiting disease is more important than the gathering of statistics.

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When the pandemic erupted, rapid coronavirus tests didn’t exist. We simply did not have the ability to rapid test our way out of a massive economic shutdown in order to contain the virus and to keep hospitals from overflowing. We had no choice but to shelter-in-place. While we flattened the curve, we squandered the opportunity to use the time to develop systemic routine testing capable of suppressing an outbreak in any jurisdiction. Now we know better.

In fact, what we’ve learned about rapid antigen testing protocols would be applicable to future pandemics, let alone any unfortunate and unforeseen developments in the current one. It could save hundreds of thousands of lives—and would have last winter, but for a deadly combination of bad policy and a grievous misunderstanding (even by some public health experts) over how to use and interpret rapid tests. And yet, to my knowledge, no formal national plan to use rapid tests to suppress an outbreak, Covid-19 or otherwise, exists. That’s a tragedy that is either waiting to happen or ready to be avoided.

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What would make you feel safe sending our kids to school this fall? Please leave your comments below.

‡Special thanks to Dr. Kristen Panthagani for the data visualizations created for this Inside Medicine article.

References and further reading:

How long are colds and the flu contagious? https://www.nhs.uk/common-health-questions/infections/how-long-is-someone-infectious-after-a-viral-infection/ and https://www.cdc.gov/flu/about/keyfacts.htm

A landmark essay in the New England Journal of Medicine by Dr. Michael Mina on how rapid tests can be used to quash an outbreak: https://www.nejm.org/doi/full/10.1056/nejmp2025631

How long is SARS-CoV-2 contagious? https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7499497/ and newer data looking at Delta https://www.medrxiv.org/content/10.1101/2021.07.28.21261295v1

Data on rapid testing regimens: https://academic.oup.com/jid/advance-article/doi/10.1093/infdis/jiab337/6311835

My initial call for testing every American (in the pre-rapid antigen test era): https://www.washingtonpost.com/opinions/2020/03/11/useful-covid-19-testing-we-need-think-outside-box-outside-er/