Teens use soft drinks to fake positive COVID-19 tests

The following is a roundup of some of the latest scientific studies on the novel coronavirus and efforts to find treatments and vaccines for COVID-19, the illness caused by the virus.

Some teens are faking positive COVID-19 tests

Teenagers have figured out how to use soft drinks to fake a positive COVID-19 test, and the authors of a new study warn schools and other groups to be aware.

As of July 1, videos uploaded to social media under the search term #fakecovidtest, featuring young people applying various liquids to rapid antigen COVID-19 tests, had been viewed millions of times, according to the British news website inews.co.uk.

That report, and others, prompted University of Liverpool researchers to study the effects of applying soft drinks and artificial sweeteners to the test swabs. All four sweeteners tested produced negative results on rapid COVID-19 tests, as did spring water.

But 10 of 14 soft drinks produced positive or weakly positive results, with no apparent link between the test results and the soft drinks’ ingredients, the researchers reported on Monday on medRxiv ahead of peer review.

Since March, UK schools have asked pupils without symptoms to test twice weekly, the authors note. A positive test can result in an entire class having to isolate at home. Based on their findings, they advise, testing “should be performed first thing in the morning, prior to the consumption of any food or drinks, and supervised where feasible.”

COVID-19 vaccines may be curbing new virus mutations

Along with preventing illness and deaths, COVID-19 vaccines may also be curbing the “rampant evolution” of the new coronavirus by limiting new mutations that allow it to evade antibodies, researchers believe. As part of a larger study, they closely analyzed gene sequences in virus samples obtained from 30 COVID-19 patients who had not been vaccinated and 23 vaccinated individuals with so-called breakthrough cases of COVID-19.

In particular, they looked at genes associated with the spike the virus uses to break into cells. The spikes are targeted by the antibodies unleashed by current treatments and vaccines.

The more the spike mutates, or changes, the less likely the antibodies will be fully effective. Compared to virus samples from unvaccinated patients, samples from vaccine breakthrough patients showed significantly fewer mutations on the spike, researchers from data analytics company nference reported on Monday on medRxiv ahead of peer review.

The more people get infected, the more opportunities the virus has to mutate as it makes copies of itself inside the body. It is possible that by suppressing the number of copies made in vaccinated people, the chances to mutate are reduced as well, the authors suggest.

“This study presents the first known evidence that COVID-19 vaccines are fundamentally restricting the … escape pathways accessible to SARS-CoV-2,” they concluded.

Rapid COVID-19 tests are generally reliable

Used properly, “rapid antigen” COVID-19 tests that give fast results are generally reliable, a new study suggests. The tests have “good” sensitivity, or the ability to correctly identify patients who are infected with the coronavirus, and “excellent” specificity, or the ability to correctly identify people who are not infected, UK researchers reported in The Lancet Microbe. Unlike gold-standard PCR tests, which involve complex lab equipment and highly trained staff, rapid antigen tests can be processed on the spot.

The researchers evaluated six commercially available tests. Compared to PCR, their accuracy at diagnosing infection varied from 65% to 89% and rose above 90% in patients with high viral loads. The researchers warn that correct use of the tests is essential, which may happen less often with members of the public than when administered by trained healthcare workers.

Although PCR-based testing is more accurate, they conclude, the rapid tests’ “versatility in terms of cost and portability,” and their usefulness in disrupting transmission from infected asymptomatic individuals who would otherwise go undetected “could outweigh the risk of missing positive cases.”