For much of the pandemic, the high sensitivity of the primary test for COVID-19 is a blessing, revealing even small amounts of the virus that can spread silently among people who may not feel sick.
But as more people are vaccinated, the sensitivity of the test raises questions among health experts about whether results should be looked at more critically when an asymptomatic immunized person is positive for COVID-19. Is this person really a threat to the spread of the virus or is he just fighting it and keeping it low to get infected?
Kevin Miller was caught in the middle of this unfortunate debate and it cost him some of the most precious moments of his high school year.
The high school student in Los Gatos had taken the opportunity to be vaccinated, receiving his last dose on February 27, so that he could return to class on campus and play basketball on the university team as soon as possible without worrying. for the virus. But on May 5, almost 1
“I had no reason to believe I had it,” said Miller, 18. “I have never been ill, I have never received a new positive test. No one else on the team did well. “
Despite three subsequent negative tests, local health and school officials said they were forced to implement safety protocols, requiring Miller and dozens of his exposed team members and classmates to be quarantined for a week, missing personal classes and games and almost to keep them attending their senior prom.
“I just felt like this situation where you can’t do these things the way it did,” said Kevin’s mother, Dana Miller.
Some health officials say the test should not have been necessary. Vaccinated people who do not feel unwell can still test positive for COVID-19 while their bodies are fighting the virus, but are not at risk of infecting others, said Dr. Monica Gandhi of the University of California, San Francisco, who studied the safety of viruses in schools.
“I think at this point we need to change our definition of what an infection is,” Gandhi said.
This is a scenario that may occur more often as more people become immunized and schools and businesses open up completely to prevent outbreaks. Although the US Centers for Disease Control and Prevention does not recommend testing COVID-19 for asymptomatic vaccinated people, there are still situations, such as some athletic competitions, in which players are tested for the virus.
This was not the first time a fully vaccinated athlete tested positive for COVID-19 without any symptoms of the disease and was forced to quarantine. Around the same time last month, nine fully vaccinated members of the New York Yankees baseball team tested positive for the virus, including stop star Gleiber Torres.
Only two reported mild symptoms, while Torres and the others were asymptomatic. But everyone was forced to quarantine. Major league baseball requires two negative COVID-19 tests for vaccinated people to get out of a 10-day quarantine early.
The CDC considers that any positive test for SARS-CoV-2, the virus that causes the disease, in humans, at least two weeks after the final dose of the vaccine, is a ‘breakthrough’ infection. A recent CDC study called these “very rare” – only 0.01% of fully vaccinated Americans this year were positive, 27% of whom showed no symptoms.
How accurate are the tests for COVID-19? The polymerase chain reaction or PCR tests commonly used to confirm COVID-19 are considered to be very accurate to some extent.
If the infection had not progressed far when the person was erased, this may not lead to a positive result, so health authorities warn that a negative test does not prove that a person is without COVID. They also consider false positives to be very unlikely. Unless the sample has been contaminated, a virus must be present.
Do the tests show the severity of the infection and the infectivity? Many experts say so.
The PCR assay analyzes samples by amplifying viral RNA or genetic material in typically 40 amplification cycles. If the virus is detected in 40 cycles or less, this is considered positive. The more cycles it takes to detect the virus, the fewer there are. A test that detects the virus in 20 cycles shows a far higher viral load on the patient than it takes 40 cycles. Patients with higher viral loads are more contagious, while low viral loads are not necessarily infectious. It is not clear what the viral load of Kevin Miller was in his positive test.
Prior to vaccines, it can be assumed that a patient with a lower viral load becomes more contagious as the disease progresses. But for those vaccinated, the low viral load that causes a positive test in a person who does not feel symptoms may simply mean that the vaccine is working.
“This shows the effectiveness of the vaccine in fighting this virus in your nose,” Gandhi said. She claims that cases like Miller or the Yankees “are not a real positive test – this is the vaccine that works!”
She is not the only health expert calling on health authorities to reconsider how PCR tests are evaluated for vaccinated people. Following the outbreak of the Yankees, Harvard University epidemiologist Michael Mina told New York magazine that the breakthrough period should be reserved for vaccinated people who become ill. He noted that effective vaccines are not usually “completely sterilized,” killing the entire virus instantly.
But other experts say caution is still warranted.
“I don’t think there’s any evidence that vaccinated people with a low viral load are less likely to be transmitted than unvaccinated people with a low viral load,” said Martha Maria Gallia, a professor of molecular biology at Tufts University, who studied how the virus COVID-19 avoids the human immune response.
Despite the debate, CDC spokeswoman Martha Sharan said the agency had no plans to change what it considered a breakthrough vaccine infection.
“The passive surveillance system we set up is not designed to assess contagion, and the data should not be used that way,” Sharan said. “Additional laboratory tests are needed to see if breakthroughs can transmit the virus. Our system aims to track people who test positive for SARS-CoV-2 after vaccination and to track trends in these cases, not to assess infectivity. “