In a move to investigate COVID-19 breakthrough infections among persons vaccinated against the virus, the U.S. Centers for Disease Control and Prevention has announced new and revised testing measures just for vaccinated individuals.
Previously, the CDC had recommended something called a PCR threshold of 40, meaning that the test would be considered positive even if it took 40 testing cycles to find a tiny shed of virus. During the height of the pandemic, critics said that threshold was too high, as it was marking people positive when they actually had only genetic fragments or leftovers from an infection that posed no risk of contagion.
The New York Times likened those tests as “akin to finding a hair in a room long after a person has left.” Criticisms aside, the high threshold testing procedure stayed in place — until now.
With more and more breakthrough cases being reported, the CDC quietly changed its PCR threshold for testing breakthrough infections to 28 or less. This means that far fewer cases will be identified as positive than were they to stay at the 40 threshold. “The entire epidemic would have very different if  had been used [for a regular infection],” Alex Berensen tweeted.
On its website, the CDC noted that it also would not test every breakthrough case, but instead would “focus on identifying and investigating only vaccine breakthrough infections that result in hospitalization or death” — a move that will also lower the total case counts among vaccinated individuals.