Can rapid COVID tests alone replace two-week destination quarantines now? It may not prove workable
Airports and airlines are hoping to restart travel by offering rapid COVID tests to replace two-week quarantines. The big question today is, “Can a single COVID test safely replace a 14-day quarantine?” Or, is it more likely to further spread the deadly virus? To answer that question, we’ve got to get somewhat technical.
Infections during the COVID-19 pandemic are accelerating at this time. COVID cases now exceed 50 million worldwide, with more than 1.2 million deaths. Many borders have closed to international travel and some U.S. states are restricting domestic travels. A lack of travel has greatly affected the travel and hospitality industries across the globe, causing significant unemployment and hardship.
For COVID safety, many nations and some U.S. states allowing travel have instituted 14-day quarantines for incoming visitors. However, that’s as long as most people have for a vacation, so they’re staying home. Is there a viable compromise that will make testing viable?
Both PCR and Antigen COVID-19 tests can have significant false-negative results
To determine if someone is actively infected with COVID-19, there are two main testing categories of tests: PCR and antigen.
PCR (Polymerase Chain Reaction) testing looks for traces of the virus’s genetic material in samples taken from noses and throats. The U.S. Centers for Disease Control and Prevention (CDC) considers PCR testing to be the “gold standard.” Studies suggest that false negatives from this test can be as high as 30 percent.
Antigen tests look for proteins that live on the virus’s surface. They take much less time than PCR to obtain test results, sometimes only minutes. While the test is fast, it’s less accurate than PCR. It has a potential false-negative rate of almost 50 percent.
When PCR and antigen tests are well-timed with samples taken by medical professionals, their false negative rates drop.
The virus’ incubation period is two weeks. But those infected with COVID-19 typically become sick within five days. Travelers who quarantine for two weeks without getting sick are safe to be with others. Travelers with false-negative COVID test results, who don’t quarantine, will likely infect many others at their destination.
False-negative test results can occur based on test type, sampling, and timing of the test.
At this time, PCR testing generally takes 24 to 48 hours to get its results. It is the most accurate test with the lowest inherent rate of false negatives. Antigen tests are faster, as noted above, but have a false negative rate as much as twice that of PCR tests.
False negatives can happen if the person taking the sample doesn’t go deep enough into the nose or throat to collect the sample. Samples taken by travelers at home are the most likely to be insufficient. The samples taken by trained medical personnel are the most likely to produce the least percentage of false positives. Samples taken by trained non-medical personnel fall somewhere in between.
In the American College of Physicians’ Annals of Internal Medicine (AIM), a study of false negative rates of PCR testing of COVID-19 (SARS-CoV-2) was published in August. The purpose of the study was to “estimate the false-negative rate by day since infection.” The study estimated that during the four days of infection prior to symptoms, typically the fifth day, the probability of getting a false negative test result ranged from 100 percent on day 1 to a mean of 67 percent on day 4.
In other words, during the course of the disease, even the best test for COVID-19 can’t accurately detect if a traveler is infected with the virus in the first days following initial infection.
A single COVID-19 test isn’t a reasonable substitute for two-week destination quarantines.
One must conclude that performing a single PCR or a more rapid antigen test is inadequate. For COVID-19, testing cannot be considered as a reasonable quarantine substitute.
New York has instituted an alternate testing/quarantine protocol. Travelers to New York must test negative for COVID-19 within 72 hours prior to their travel to the state. After three days of self-quarantine, they must be retested. If that test is negative they are free to leave quarantine. That’s an improvement, but the AIM study discussed above leads me to believe this protocol needs modification.
A protocol including a three-day destination quarantine bookended with COVID PCR tests may be a viable substitute for two-week destination quarantines
I suggest requiring a negative COVID PCR test for travelers taken 72 to 48 hours prior to their trip’s departure. No day-of-departure testing would be permissible. At departure, travelers would be checked for symptoms. Upon arrival at their destination, travelers would quarantine for 72 hours, then be retested by PCR or antigen tests. That would put the second test on at least day 5, a day when many people become symptomatic, and when the false-negative test rate has significantly dropped.
While not quite as safe as quarantine, this protocol could be a viable compromise that would keep people safe while enabling travel to restart once the pandemic is better controlled than it is today.
After many years working in corporate America as a chemical engineer, executive and eventually CFO of a multinational manufacturer, Ned founded a tech consulting company and later restarted NSL Photography, his photography business. As a well known corporate, travel and wildlife photographer, Ned travels the world writing about travel and photography, as well as running photography workshops, seminars and photowalks. Visit Ned’s Photography Blog and Galleries.