Since the spring, many public health experts have been calling for rapid, at-home, over-the-counter Covid-19 tests for people without symptoms. The Food and Drug Administration (FDA) finally authorized the first one Tuesday, potentially ushering in a new approach to combating the pandemic, which is projected to continue taking thousands of US lives each day through the winter and early spring.<\/p>\n
These home tests would work alongside the standard, lab-based PCR tests that have been the backbone of testing in the US but have often been too slow at catching infections before they spread. Rapid at-home tests, like the recently greenlit one from Ellume, could alert people they have the virus before they start feeling sick \u2014 and even if they never get symptoms at all.<\/p>\n
The new Ellume Covid-19 Home Test uses a nasal swab mixed with a specialized fluid to generate results on a small device that connects via Bluetooth to a smartphone app. \u201cBy authorizing a test for over-the-counter use, the FDA allows it to be sold in places like drug stores, where a patient can buy it, swab their nose, run the test, and find out their results in as little as 20 minutes,\u201d FDA Commissioner Stephen Hahn said in a statement. <\/p>\n
The Ellume product joins two other rapid at-home tests, both of which require prior approval or a prescription and are for people with suspected Covid-19 cases: the BinaxNOW COVID-19 Ag Card Home Test made by Abbott, which got an EUA Wednesday, and the Lucira COVID-19 All-In-One Test Kit, approved in November.<\/p>\n
This rush of new approvals is exciting to many who have been following these tests for months. \u201cThis is great news to put testing in the hands of people who need it,\u201d says Gigi Kwik Gronvall, an immunologist and senior scholar at the Johns Hopkins Center for Health Security, who has been leading the center\u2019s test tracking. <\/p>\n
It \u201cshows that we\u2019re getting to another level of access to timely testing, and hopefully that trend is going to continue,\u201d says Mark McClellan, director of the Center for Health Policy at Duke University who served as FDA commissioner under President George W. Bush. More than two dozen similar tests are reportedly in the works, using a variety of methods \u2014 looking for viral proteins or scraps of genetic code \u2014 to tell people if they have high levels of the virus in their system. <\/p>\n
\u201cBut I think people shouldn\u2019t get too far ahead of themselves,\u201d McClellan says. \u201cThe supply of these tests is not in line with what you would need for routine testing for lots and lots of Americans.\u201d Ellume, for example, is expecting to be able to roll out 100,000 tests per day in January, scaling up to 1 million tests per day by June. To test 330 million people in the US twice a week, as some experts are recommending, we\u2019d need about 94 million tests a day. <\/p>\n
And even at scale, these new at-home tests cannot solve our pandemic problems on their own. We\u2019ll continue to need to wear masks, maintain social distancing, and get vaccines as soon as we can. \u201cRelying on testing and the personal responsibility of people to take these tests on a regular basis is not going to be the only thing to get us out of this mess,\u201d Kwik Gronvall says. <\/p>\n
Here\u2019s why, and what we \u2014 and the Biden administration \u2014 need to do next. <\/p>\n
At-home tests face major hurdles, but Ellume cleared many of them<\/p>\n
Most Covid-19 tests conducted in the US so far have been PCR tests. These require a laboratory and specialized equipment, along with trained personnel, to multiply viral material from a sample up to a detectable level. This makes them quite (if not perfectly) reliable in diagnosing infections. <\/p>\n
But it has also made them prone to major delays, as laboratories got backlogged during spikes. This meant results have sometimes taken a week or more to return, making these tests impractical for helping people not spread the virus.<\/p>\n
\u201cEssentially all of the testing that is happening in this country right now is without purpose\u201d when there are multiple-day delays in returning results, Michael Mina, an epidemiologist at the Harvard T.H. Chan School of Public Health and advocate for rapid testing, said in a call with reporters earlier this month. <\/p>\n
The whole idea behind at-home \u2014 or \u201cat-anywhere\u201d \u2014 tests is that they don\u2019t require a lab and a professional to run them. They provide quick results so that people can isolate themselves immediately, if necessary. <\/p>\n
But there have been major concerns about sidelining advanced equipment and trained staff while determining whether someone is infected. \u201cA first law of testing is that everyone wants a lab test to be cheap, fast, and accurate,\u201d says Geoffery Baird, chair of laboratory medicine and pathology at University of Washington Medicine. But, he says, of those three requirements, \u201cYou only get two. … What normally happens when people are making that trade-off is that they give up accuracy.\u201d <\/p>\n
One issue he and others worry about is the opportunity for user error. \u201cThe performance of all these tests is always worse out in the field than when it\u2019s data submitted to the FDA,\u201d Baird says. He also oversees the toxicology lab at the county hospital, where they field questions about over-the-counter home tests for drugs, and he sees a lot of issues from people trying to use those tests by themselves. People can misunderstand the instructions or collect the sample incorrectly, for example. <\/p>\n
Two other challenges with testing at home, especially with a test people buy over the counter, are getting people connected to a medical professional for appropriate care or follow-up testing, and getting test results reported to public health authorities. <\/p>\n
First, nuances in an individual\u2019s situation might warrant different responses to a test result than a simple positive or negative might tell them, Baird notes. For example, someone with Covid-19 symptoms who receives a negative antigen test result might still be recommended for follow-up PCR testing to help verify they really don\u2019t have the virus. On the other side, someone who tests positive but doesn\u2019t have any symptoms or known exposures might also need follow-up, especially if they live in an area where there isn\u2019t much virus circulating. These are all considerations a health care provider could walk someone through perhaps better than an app can.<\/p>\n
Second, many experts have been advocating for low-tech, simple paper strip-based tests \u2014 akin to a pregnancy test \u2014 but that might mean that results are off the grid, keeping public health officials in the dark about where and how much the virus was spreading. \u201cThis is a concern \u2014 how are you going to get accurate counts of positive cases at the same time as giving people access to testing,\u201d Kwik Gronvall says. <\/p>\n
Ellume went higher-tech with its new test, ensuring results \u2014 transmitted via Bluetooth to the linked smartphone app \u2014 would be automatically transferred (with the person\u2019s zip code and date of birth; name and email are optional) to public health officials. But the technology also nudged the price tag up from the $1 to $5 that Mina has proposed to $30. This would make frequent testing unlikely for someone earning, for example, the federal minimum wage ($7.25 per hour) and paying for it out of pocket. <\/p>\n
Abbott\u2019s newly greenlit at-home test took a different route. It kept the test itself low-tech, but it requires interaction with a professional \u201ccertified guide\u201d through an online medical service, who can advise people on best next steps and also report test results to public health channels. This means the test (which itself costs $5) actually retails for $25 to cover the cost of the professional\u2019s time. Abbott\u2019s test also requires people to meet the criteria of being in the first seven days of having symptoms (which also means not everyone can take it), and it takes extra time for the kit to be shipped. <\/p>\n
People have also raised concerns over how these tests work. The method that many companies are pursuing, and the one the Ellume and Abbott tests use, is to seek out specific proteins on the virus cells called antigens (not to be confused with antibodies, which are proteins the body makes to find an infection and can indicate if someone was exposed to the virus in the past). But without expensive equipment, these tests have generally needed high virus levels to produce a positive result that could be read at home. Compared to PCR tests, many antigen tests have missed some of the positive cases.<\/p>\n
The Ellume test, in its small study of about 200 people, was able to jump up to close to PCR levels of sensitivity \u2014 detecting 96 percent of the people with symptoms that PCR also found \u2014 and of specificity, returning a negative result for all the people who also got a negative PCR test. Perhaps even more crucially, for those without symptoms, it picked up 91 percent of infections, and delivered correct negative results to 96 percent of people who didn\u2019t have the virus. To get FDA authorization, the Abbott and Lucira tests had to achieve similar levels of accuracy. <\/p>\n
But many experts see the accuracy difference with these antigen kits less as a shortcoming and more as a new way to approach testing. <\/p>\n
The power of less sensitive tests <\/p>\n
From a medical diagnostic perspective, a traditional PCR test can tell if someone has even a very small amount of the SARS-CoV-2 virus. This is incredibly helpful to doctors who are trying to figure out the best way to treat an ill patient, for example, as people who are very sick with Covid-19 actually often have smaller amounts of the virus left in their system. But PCR\u2019s slower turnaround means that it doesn\u2019t always help us find people who are most at risk of spreading the virus to others.<\/p>\n
In fact, it rarely does. According to Mina, less than 5 percent of tests currently being done are returning results while people are still infectious. \u201cLab PCR testing probably should never have been a public health tool; it\u2019s a medical tool,\u201d Mina said. \u201cThat needs to be reserved for medical use, for people who are sick, for people who are in the hospital.\u201d<\/p>\n
There are two intertwined reasons for this. First, unlike previous severe coronaviruses, such as SARS and MERS, Covid-19 spreads most readily just before and just as someone develops symptoms. As soon as someone catches the virus, it begins multiplying in their system, usually making them infectious around day two to four. However, people often don\u2019t develop symptoms until day four or five after exposure. That means many people spread the virus in the 24 to 48 hours before they feel sick. (And this is to say nothing of the 40 percent or so of people who have the virus \u2014 at similarly infectious levels \u2014 and never develop symptoms.)<\/p>\n
Offering these rapid, at-home tests to people without symptoms, as the Ellume authorization has, could play a powerful role in monitoring and slowing the virus\u2019s spread.<\/p>\n
The second reason these quick tests could help substantially is that time is of the essence, and PCR testing has been very slow. Let\u2019s say someone waits until they have had symptoms for a couple of days, gets a PCR test, and then waits four days for the results. It\u2019s likely that by the time a positive result is returned, that person isn\u2019t even infectious anymore. \u201cEven a 24- to 48-hour delay in testing, which right now is rapid for PCR tests, it\u2019s just not going to stop spread,\u201d Mina said. <\/p>\n
That\u2019s why he and others have been advocating for the quick at-home antigen tests. Although less sensitive at-home tests might not pick up the very small levels of the virus that PCR tests can, they should be able to detect higher levels, which is exactly when people are most likely to spread the virus, whether or not they have symptoms. <\/p>\n
\u201cAntigen tests have been much maligned and much misunderstood \u2014 and have a really, really important role to play in this pandemic,\u201d says Ashish Jha, health policy expert and dean of the Brown School of Public Health. <\/p>\n
Kwik Gronvall agrees: \u201cThey have some really great advantages as far as giving you actionable information in a timely manner.\u201d <\/p>\n
Many experts point out that with a 90 percent rate at catching infections, that\u2019s 10 people out of 100 that might be spreading the virus unknowingly (assuming they are still infectious). When you scale up to millions of tests, if 1 million people tested are positive, 100,000 of those infections could be missed. Which sounds pretty bad. <\/p>\n
But this is why these tests are not a replacement for other scientifically backed public health practices. Rather, they are another layer in the \u201cSwiss cheese\u201d model of using many imperfect methods concurrently to stop viral spread. Many questioners of rapid tests have pointed to the outbreaks at the White House that occurred while people were being tested frequently.<\/p>\n
So this example doesn\u2019t actually present a case against these tests, but illustrates how not to use them. Instead of testing everyone and allowing everyone with a negative result to waltz into large events \u2014 or into their grandfather\u2019s living room \u2014 without a mask or social distancing, these tests should alert people with a positive result to self-isolate and get in touch with their health care provider. Those with a negative result could continue with carefully masked and distanced activities. \u201cTesting doesn\u2019t make things safe by itself; it adds protection to things you\u2019re already doing,\u201d Baird says. <\/p>\n
Besides, most of those hypothetical 100 people in the testing scenario probably wouldn\u2019t have otherwise gotten tested then. \u201cThe alternative is what we have now, which is out of 100 people with the disease almost no one is getting a test,\u201d Jha says. \u201cSo would you like to pick up 90 out of 100 or would you like to pick up zero out of 100?\u201d<\/p>\n
\u201cI\u2019d love a perfect test, but these are compromises that don\u2019t, in my mind, substantially affect the value of these tests,\u201d Jha notes. <\/p>\n
How we could use rapid at-home testing to slow the pandemic <\/p>\n
For all of their strengths and all of the enthusiasm surrounding them, rapid at-home Covid-19 tests are not meant to become the new solution for those of us waiting for our vaccine. Nor are they meant to be the only form of testing we do. <\/p>\n
Even the most vocal advocates for widespread at-home testing are simply pushing for these tests to become an additional testing tool, alongside PCR and other techniques. \u201cYou want to have the ability to do PCR testing for verification,\u201d Jha says. \u201cNo one is saying throw out PRC testing, and none are saying do antigen testing and don\u2019t worry about anything else.\u201d <\/p>\n
Above all, these tests need to be part of a comprehensive testing strategy for the incoming Biden administration, Jha says. <\/p>\n
This will be especially important in the early days when these tests have limited supply. \u201cWe should be deploying them in nursing homes, schools, health care facilities, high-risk workplaces like meatpacking plants, and for other essential workers like police officers, firefighters, and EMTs,\u201d Jha says. <\/p>\n
For now, among the newly authorized at-home rapid tests, \u201cwe\u2019re talking about maybe 20 million to 30 million tests per month, which is not anywhere near enough to do large-scale testing,\u201d McClellan says. So although \u201ctest capacity is increasing a lot, from the standpoint of maximizing public health impact for the next three to six months … we\u2019ve got to prioritize [rapid testing] to settings where it\u2019s going to have the most impact.\u201d <\/p>\n
The Trump administration has done this to some extent with previously approved rapid antigen tests (for use by trained professionals), now purchasing some 50 million Abbott BinaxNOW professionally administered tests each month and sending many directly to long-term care facilities and other priority locations. This ensures \u201cthat the tests go not just to people who can afford to buy it but the places where we need it the very most,\u201d McClellan notes. <\/p>\n
But if the Ellume and other at-home tests are simply released to pharmacies and other marketplaces for anyone to buy, Jha thinks the limited number of tests are most likely to be bought up by companies to test their employees and by people who are looking to travel or see others in person. So he says he doubts that, for now, these tests will actually do much to change daily life. <\/p>\n
As more people in high-priority groups receive the vaccine, however, more of the testing might be allocated away from these folks and to the general public, McClellan notes. And, in the meantime, we should all be doing our part to reduce demand for the limited supply of tests by staying at home and not gathering, Baird says. <\/p>\n
But to see a big impact, we are going to need not only strategic allocation but also, eventually, a lot more tests. \u201cIn an ideal world, you\u2019d be testing everybody in America twice a week,\u201d Jha says. He also recognizes that this level of testing isn\u2019t likely to be feasible (or even necessary if many people continue to stay home and take adequate precautions). So he proposes that \u201cif we want to save lives and bring our economy back, we need 10 million to 20 million tests a day.\u201d (So far we have yet to cross 2 million tests given per day in the US.)<\/p>\n
This is because, regardless of the method of testing, Kwik Gronvall notes, \u201ctesting is a moment in time, and it can\u2019t be the only thing that you do to prevent transmission.\u201d <\/p>\n
How we can get rapid at-home tests for everyone, often<\/p>\n
Getting more rapid tests authorized, made, and distributed is contingent on the Trump and Biden administrations making it a priority. From his conversations with members of the Biden advisory and transition teams, Jha says the incoming administration \u201cis really focused on ramping up testing across a variety of modalities, and that includes rapid testing.\u201d That is, he says, because they understand that even after more people can get a Covid-19 vaccine, the virus will still be circulating in the US for a while \u2014 and abroad even longer. We also don\u2019t yet know if people who have gotten the vaccines can still carry and spread the virus easily, even if they themselves don\u2019t get sick. <\/p>\n
Jha suggests four things the Biden administration should do right away to improve the testing situation: <\/p>\n
Getting more rapid at-home tests to more people on a regular basis also depends on Congress to fund these efforts. Mina has been lobbying members of Congress to dedicate $1 billion of the potential $900 billion pandemic stimulus package to bringing more rapid tests to market (which could come from the $16 billion in the bill earmarked for vaccines, testing, and tracing). <\/p>\n
\u201cIt sounds like a lot of money,\u201d he said. But \u201cit\u2019s less than 0.05 percent of what this virus is likely to cost Americans over the next few months.\u201d He recommends a $200 million boost each to five companies that already have these tests developed to scale up manufacturing. From there, he suggests $5 billion to $10 billion earmarked for manufacturing and distribution in 2021. <\/p>\n
With this backing, Mina says, \u201cwe could find ourselves in an entirely different position\u201d than the current tragic death tallies. Even with the vaccine rolling out, one major model puts the expected new toll at more than 101,000 additional US deaths by February 1 (if universal masking isn\u2019t adopted; 78,000 if it is). This means testing will remain critical. <\/p>\n
McClellan agrees. If the Biden administration rapidly invests even more money in scaling up manufacturing of these tests, the US could have even more available for early 2021. \u201cSo I think it\u2019s not unreasonable to expect that schools who want it and other priority settings that really want it should be able to get it,\u201d he says. <\/p>\n
But that also depends on the FDA being able to greenlight more of these tests. McClellan notes that rapid, at-home testing \u201cis a high priority for the FDA.\u201d <\/p>\n
Mina and others have called for a new pathway to get these tests to market that doesn\u2019t hold them to the same diagnostic criteria as PCR tests. And McClellan says the FDA is discussing options for authorizing Covid-19 tests less sensitive, for example, than Ellume\u2019s. One way to do this would be to instruct that such tests are to be used frequently \u2014 multiple times a week \u2014 to increase the odds that they will catch an infection. <\/p>\n
So long as the tests are thoughtfully authorized and deployed, if we can add relatively widespread, rapid testing to a more comprehensive plan to fight the pandemic, Jha says, \u201cI see a pretty bright spring. Not normal, not spring of 2019, but a lot better than the spring of 2020.\u201d Americans won\u2019t be going to packed concerts, and they will continue to need to wear masks and continue distancing, but many essential functions will be more solid. \u201cThere will be little to no justification for not having schools open,\u201d he says. <\/p>\n