The Mayo Clinic and Cambridge-based biotech company nfrence conducted the study, posted in medrvix last week, by analyzing samples of delta variant prevalence in Minnesota from January to July.
When asked if this indicated that individuals should seek a Moderna dose for the booster shot, Fauci disagreed.
"That study … is a pre-print study, it hasn’t been fully peer-reviewed," Fauci said on CBS's "Face the Nation." "I don’t doubt what they’re seeing, but there are a lot of confounding variables in there, about when one was started, the relative amount of people in that cohort who were delta vs alpha – right now, if we get boosters … it’s clear we want to make sure we get people, if possible, to get the boost from the original vaccine."
Fauci once again stressed that he hopes full authorization occurs soon, which will help bolster vaccination efforts.
Centers for Disease Control Director Dr. Rochelle Walensky on Friday approved booster shots for moderate-to-severe immunocompromised individuals, which would utilize either a Pfizer or Moderna dose.
A panel of independent experts determined that the booster shots were a necessary step. Patients eligible for booster shots under the recommendation and amended emergency approval include those with moderate to severe immune system compromise, such as solid organ transplant recipients, patients with advanced or untreated HIV infection, and those taking high-dose corticosteroids and treatments for cancer, among others.
When asked about plans for how to determine new groups to authorize for booster shots, Fauci advised that the government will continue to monitor data on a "daily and weekly basis" to determine if, when, and to whom they will distribute booster shots.
Fox News’ Kayla Rivas contributed to this report.