The studies that prompted the Centers for Disease Control and Prevention (CDC) to change their mask guidance for vaccinated persons are not available, a spokesperson told The Epoch Times on Wednesday.
“They have not been published yet,” the spokesperson said.
Dr. Rochelle Walensky, the CDC’s director, told reporters on July 27 that she had seen “new scientific data from recent outbreak investigations” indicating the Delta variant of the virus that causes COVID-19 was presenting more uniquely than other strains.
“Information from several states and other countries indicates that in rare occasions, some vaccinated people infected with the Delta variants after vaccination may be contagious and spread the virus to others,” she said.
That motivated officials at the agency to change masking guidance. Fully vaccinated persons, told two months ago they could stop wearing masks indoors, are now being told to don the coverings when inside.
Multiple states and businesses quickly adopted the recommendations.
But the CDC’s webpage outlining the new advice does not cite any studies or research.
A related science brief linked on the page cites a single study from the United States when discussing the data Walensky mentioned.
That study came from researchers at Houston Methodist, a hospital system in Texas in the news recently for mandating all employees get a COVID-19 vaccine.
Researchers said that the Delta variant caused a higher rate of breakthrough cases, or infections among the vaccinated.
The study is preprint, meaning it is not yet peer-reviewed. The medRxiv platform, which hosts the preprints, warns not to use such studies “to guide clinical practice.”
The CDC also cited “studies from India” that “noted relatively high viral loads and larger cluster sizes associated with infections with Delta, regardless of vaccination status.”
The studies concern vaccines not authorized for use in the United States. The study sourced in footnotes on the page has not been peer-reviewed and was listed as “reject after peer review.”
“These early data suggest that breakthrough Delta infections are transmissible. Unpublished data are consistent with this, and additional data collection and studies are underway to understand the level and duration of transmissibility from Delta vaccine breakthrough infections in the United States and other settings,” the CDC stated.
The CDC spokesperson told The Epoch Times they did not know if the Texas and India studies were used to inform the mask guidance change.