As millions of Americans get vaccinated for COVID-19, many of us are starting to hope those painful nose swab tests will soon be a thing of the past.
Alas, the future of COVID-19 testing is more complicated than “less testing,” especially as we head into a potential fourth surge of cases. Testing is still a valuable tool in our COVID-19 prevention toolkit, but the technologies and motivations behind it are shifting. We’ll also have to shift our understanding of test results and metrics. To interpret the test numbers on the news or your local public health department’s website, there are two patterns you should think about: who will be tested less in the coming months and who will be tested more.
That first group is easier to predict: It’s those of us who have been vaccinated. As of April 11, more than one-third of the U.S. population has received at least one dose of a COVID-19 vaccine, and one-fifth is fully vaccinated. While some experts are careful to specify that we don’t yet have data on whether the vaccines prevent coronavirus spread from one person to another, the data we do have suggest transmission is unlikely.
As a result, if you’ve been vaccinated and are experiencing cold or allergy symptoms, you probably won’t need to go get a PCR test just in case, as you might have had to do previously. And if you were getting tested every two weeks to check your COVID-19 status before you got vaccinated, you likely aren’t doing that as often, if at all. This will likely mean a decrease in what epidemiologists call diagnostic testing, tests that are used to provide an answer to a specific patient who suspects they have COVID-19.
“Some of the symptomatic testing is going down just because vaccines work,” says Mara Aspinall, diagnostic testing expert and managing director of the Health Catalysts Group. Still, “we can’t stop testing.” That’s especially true with concerning variants spreading across the country. At the individual level, tests are a tool to tell you if you have COVID-19; but at the community level, they can tell the local public health department how much coronavirus spread is currently taking place.
You can explore the need for continued testing through this modeling tool, developed by health tech company Color Health and University of Washington researchers Carl Bergstrom and Ryan McGee. Until the majority of a population is vaccinated, the model shows, we’ll need some level of regular testing. So we won’t necessarily see a huge drop in test numbers overall. Rather, more people may have the opportunity to get tested if they need it, and the way we use tests may change to a more community-centric mindset.
Plus, of course, even those who have been vaccinated may still be able to get sick with COVID-19. These cases—which experts call breakthrough cases—have been incredibly rare so far, but continued testing will be key as public health experts monitor vaccine safety.
There are parts of the country that still struggle with diagnostic testing. A FiveThirtyEight study published in July found that Black and Hispanic neighborhoods had far less access to testing sites than white neighborhoods; while more resources have poured into testing sites since then, gaps like these are hard to fill.
“I do worry that a lot of the testing efforts for underserved areas will be pulled back [as vaccinations increase],” says Saskia Popescu, infectious disease epidemiologist at George Mason University and the University of Arizona. “So I feel it’s important that we focus on stable and sustainable testing and vaccination resources in those vulnerable areas and neighborhoods.”
If local public health departments and community partners play their cards right, we could see those surplus tests that vaccinated Americans no longer want going into previously underserved areas and helping to control previously underreported outbreaks.
The question of who will get tested more amid vaccination is more complicated to answer. Tests may become more regular fixtures for travelers as Americans take long-awaited vacations this summer. The Centers for Disease Control and Prevention and many foreign countries require a negative test for international travel, even if you’ve been vaccinated, while those traveling domestically may still want a negative test as an extra precaution before or after a trip.
It’s not only the use of testing that will shift but the kinds of tests being used. As individuals feel more protected by the vaccine and seek out fewer diagnostic tests, tracking community spread may be better met not by precise-but-slow PCR tests but by rapid, at-home tests, a major area of investment for the federal government in recent months.
In late March and early April, the Food and Drug Administration gave emergency use authorization to several rapid tests, adding to a growing arsenal of tests that are now available. Three of the newly authorized tests are permitted for over-the-counter use, meaning you may soon be able to pick up a test at your local pharmacy and administer it yourself at home, no doctor’s note or urgent care visit required—just like a pregnancy test.
That same week, the CDC and National Institutes of Health announced a new study that will evaluate how well these do-it-yourself tests actually work in preventing outbreaks. Up to 160,000 people in Pitt County, North Carolina, and Chattanooga/Hamilton County, Tennessee, will get free access to antigen tests, which they can administer themselves up to three times a week for one month. A free app will provide testing reminders, instructions, and a way to report results.
This study is a big deal for some of the experts who have long advocated the potential of rapid tests for surveillance. Unlike PCR tests, which look for coronavirus genetic material and may make patients wait several days for a result, antigen tests detect a COVID-specific molecule on the surface of a virus; this process can happen in as few as 15 minutes. Even though antigen tests have a higher rate of false negatives than PCR, their advocates argue, millions of Americans testing themselves before they go to work each morning would catch more cases than a fraction of that population getting tested only when they feel sick.
The new study will show how well rapid tests live up to their potential at a broad, community level, says Dan Larremore, a statistician at the University of Colorado (and one of those advocates). “If people can … use a boatload of rapid tests regularly for a few weeks, and we can watch the new cases spike as we find those positives and then crash as we break all the transmission chains, that’s the thing I’m looking out for in these new trials.”
If rapid tests are, indeed, shown to be good at breaking transmission chains, their widespread use can help prevent future outbreaks as coronavirus variants circle through a mostly vaccinated U.S. Rapid testing comes with its own communication challenges, though—especially if someone tries to use one for an individual diagnosis. “A negative test is one moment in time and antigen testing really has been most utilized and successful in symptomatic people,” Popescu says. “It’s important we stress the nuances of rapid testing and where it can be utilized most successfully.”
Finally, we should expect to see more testing in one group of Americans who won’t be vaccine-eligible for a while yet: kids. While clinical trials are now in place to determine vaccine efficacy and safety in children (and early results have been promising), it will likely be late 2021 before anyone under 16 is able to get a shot. As a result, kids have become a testing priority.
The Biden administration devoted $10 billion to K–12 school testing via the American Rescue Plan. Organizations like the Rockefeller Foundation are showing how that money can be put to good use by facilitating partnerships between school districts and testing labs. The foundation developed a National Testing Action Program, intended to give schools a road map to testing-supported reopening. Key points of the plan include screening students once a week and staff twice a week, and clear communication among everyone in a school’s broader community.
“Testing builds confidence and comfort in going back to school,” says Aspinall, who serves as an adviser to the Rockefeller Foundation. Parents may be more keen on opting into in-person learning when they know that any cases among their children’s peers or teachers will be easily identified.
And it’s not just schools that may adopt this type of regular testing, either. Many college campuses have used rapid tests to screen their students for months already, as have nursing homes and other health settings. Some offices are using rapid tests to screen employees who come back to working from work, and New York Gov. Andrew Cuomo has proposed rapid tests as a way to clear people for attendance at entertainment venues.
Diagnostic testing will change with vaccination and public health priorities, while more schools and workplaces start screening their entire communities and rapid, at-home testing becomes more easily accessible. What does all this mean for the numbers on your local dashboard?
Test positivity is still a valuable metric to examine the success of diagnostic testing, Popescu says. In other words: Yes, we still want to see below a 5 percent PCR test positivity rate, even as vaccination rates go up. (Five percent is a widely used benchmark recommended by the World Health Organization.) If more than 5 percent of diagnostic tests done in a state or city are coming back positive, that suggests that a lot of people are currently infected with the coronavirus and the virus may be spreading quickly. It can also mean that some cases are being missed. A higher rate can be caused by a lower denominator; in other words, not enough people are getting tested in that region because some sick people either can’t access a test or don’t know that they’ve been exposed. Michigan, which may be a harbinger for a fourth surge, has seen a positivity rate over 15 percent for diagnostic tests in the first week of April.
Since tests used for screening in a school or business cast a wider net (rather than mainly testing those who think they may be sick or have a likely exposure), the test positivity target for these tests should be lower. Jesse Papenburg, pediatric infectious disease specialist at McGill University, suggests 1 or 2 percent as the danger threshold to watch out for.
In short: If you’re monitoring testing data on your local COVID-19 dashboard, look out for a 5 percent positivity rate among diagnostic, PCR tests. But if you are getting email updates on testing at your kids’ public school, look for a 1 or 2 percent rate.
Test turnaround time, or the length of time a test result takes to reach a patient, is also a key metric to measure how easily accessible tests are for a specific community, Papenburg says. It is less commonly reported, but if your public health department does make the information available, look for a turnaround time of one day or less. The more quickly a test result arrives, the more quickly a patient can go into quarantine and contact tracers can get to work—and the more easily low-wage workers who can’t afford a day off can get tested.
Rapid tests are harder to follow. The U.S. doesn’t have standardized data pipelines for antigen tests or other forms of rapid tests as exist for PCR tests, and such data are not published by the Department of Health and Human Services or CDC. While some individual states do publish rapid test numbers, these figures are generally assumed to be significant undercounts.
This is definitely a pain point for some researchers: When you don’t know how many rapid tests are being used in your community, much less how many are coming back positive, you can’t use the information to make judgments about where the coronavirus is circulating or whether the tests are effectively catching cases and preventing outbreaks. Public health departments at every level should strive to improve their rapid test reporting in the coming months.
Still, Larremore thinks there’s a bright side to this dilemma: Rapid, at-home tests may be preferable for those who would rather keep their COVID-19 status private. “As much as I would like to know exactly what is happening with the pandemic,” he says, “if the trade-off for lower cases is that we don’t know about a lot of cases among folks who would rather not report their data, I think that’s a fair trade-off.”
In the absence of standardized government data, we can watch the NIH study to see how well rapid tests work, along with schools, workplaces, and other settings that use rapid tests for screening. We may also see other testing technologies become more widely available in the coming months, such as anosmia screens, wastewater testing, and COVID-sniffing dogs; each new test type will come with its own data needs and challenges.
As we enter a vaccinated summer and look forward to the next cold-weather months, your favorite local COVID-19 dashboard may shift functions or add new test types to its array of data. But by thinking back to the two purposes of testing—first, finding out if individuals are sick, and second, identifying infection levels in a population—you can roll with the changes and continue monitoring your community.