In much of the pandemic, the sharp sensitivity of the primary test for COVID-19 has been a boon, as it has itself detected small amounts of the virus that can spread silently among people who may not feel ill.
However, as more people are vaccinated, the sensitivity of the test raises questions among health experts as to whether the results should be viewed more critically when an asymptomatic immunized person is tested positive for COVID-19. Is this person really a threat to spread the virus or just fight it and keep it at levels too low to be contagious?
Kevin Miller was caught in the middle of the unfortunate debate, and it cost him some of the most precious moments in his high school.
Los Gatos High School student had skipped the opportunity to be vaccinated and received his final dose on Feb. 27 so he could return to class on campus and play basketball on the college team as quickly as possible without worrying about the virus. But on May 5, almost 1
“I had no reason to believe I had it,” said Miller, 18. “I never felt sick, never got another positive test. No one else on the team tested positive. ”
Despite three subsequent negative tests, local health and school staff said they were forced to implement safety protocols that required Miller and dozens of his exposed teammates and classmates to be quarantined for a week, lacking personal classes and games and almost keeping them from attending their senior prom.
“It just felt like this situation where you can’t make these things the way this unfolded,” said Kevin’s mother, Dana Miller.
Some health officials say the trial should not have been necessary. Vaccinated people who do not feel sick may still be able to trigger a positive COVID-19 test while their body fights the virus but is not at risk of infecting others, said Dr. Monica Gandhi at the University of California-San Francisco, who has studied virus safety in schools.
“I think we need to change our definition of what an infection is at this point,” Gandhi said.
It’s a scenario that is likely to come up more often as more people are immunized and schools and businesses reopen fully in order to prevent outbreaks. Although the U.S. Centers for Disease Control and Prevention does not recommend COVID-19 testing for vaccinated people without symptoms, there are still situations like some athletic competitions where players are screened for the virus.
It was not the first time that a fully vaccinated athlete tested positive for COVID-19 without symptoms of the disease and was forced to quarantine. Around the same time last month, nine fully-fledged members of the New York Yankees baseball team tested positive for the virus, including star shortstop Gleyber Torres.
Only two reported mild symptoms, while Torres and the rest were asymptomatic. But all were forced to quarantine. Major League Baseball requires two negative COVID-19 tests in order for the vaccinated to complete a 10-day quarantine early.
The CDC considers any positive test for SARS-CoV-2, the virus that causes the disease, in a person at least two weeks after their final vaccine dose to be a “breakthrough” infection. A recent CDC study called them “very rare” – only 0.01% of fully vaccinated Americans this year tested positive, of which 27% showed no symptoms.
How accurate is the COVID-19 test? The polymerase chain reaction or PCR test commonly used to confirm COVID-19 is considered very accurate to a point.
If the infection had not gotten far when the person was injured, it might not have triggered a positive result, so health authorities warn that a negative test does not show that a person is COVID-free. They also consider false positives to be very unlikely. Unless the sample was contaminated, some virus must be present.
Do the tests indicate the severity of infection – and contagion? Many experts have argued that it does.
The PCR test analyzes samples by amplifying viral RNA or genetic material in typically 40 amplification cycles. If the virus is detected in 40 cycles or less, it is considered positive. The more cycles it takes to detect the virus, the less there is. A test that finds the virus in 20 cycles indicates a much higher viral load in the patient than one that takes 40 cycles. Patients with higher viral loads are more contagious, while low viral loads are not necessarily contagious. It is not clear what Kevin Miller’s viral load was on his positive test.
Before vaccines, it is assumed that a patient with a lower amount of virus will become more contagious as the disease progresses. However, for those vaccinated, a low viral load that triggers a positive test in a person who does not feel any symptoms may simply indicate that the vaccine is doing its job.
“It shows the effectiveness of the vaccine in fighting that virus in the nose,” Gandhi said. She argues that cases like Miller or the Yankees “were not a true positive test – it was the vaccine that worked!”
She is not the only health expert urging health authorities to reconsider how PCR tests are evaluated for the vaccinated. After the Yankees outbreak, Harvard University epidemiologist Michael Mina argued in New York magazine that the breakthrough time should be reserved for vaccinated people who became ill. He noted that effective vaccines are generally not “fully sterilizing”, killing all the virus immediately.
But other experts say caution is still warranted.
“I do not think there is any evidence that vaccinated people with low viral load are less likely to transmit than unvaccinated people with low load,” said Marta Maria Gaglia, a professor of molecular biology at Tufts University who has studied how COVID-19 virus avoids human immune response.
Despite the debate, CDC spokeswoman Martha Sharan said the agency has no plans to change what it considers a vaccine breakthrough infection.
“The passive surveillance system we have set up is not intended to evaluate contagion, and the data should not be used that way,” Sharan said. “Further laboratory-based studies are needed to understand whether breakthrough cases can transmit the virus. Our system is designed to track people who test positive for SARS-CoV-2 after vaccination and to track trends in these cases, not evaluate infectivity. ”