• White House chief medical advisor Dr. Anthony Fauci told CNBC on Tuesday that Covid booster shots are currently unnecessary.
• Fauci’s comments come amid a flurry of questions on the necessity of booster shots as new coronavirus variants spread.
• The longtime head of NIAID said that talk around booster shots “has absolutely nothing to do with the effectiveness of the vaccine.”

White House chief medical advisor Dr. Anthony Fauci told CNBC on Tuesday that Covid booster shots are currently unnecessary.

"The discussion about boosters is really an appropriate preparation on the part of the [drug] companies together with the NIH and the CDC and others in being prepared in the eventuality that you might need a boost," Fauci said on "Squawk Box."

"But when you translate that into, 'We will need a boost; everyone's going to get a boost,' that is not appropriate. We still haven't vaccinated enough people in the primary part of this," he added, stressing the discussion around boosters "has absolutely nothing to do with the effectiveness of the vaccine."

Ahead of schools reopening in the fall and the spread of new coronavirus variants, questions are swirling about the necessity of booster shots, even as the pace of initial vaccinations has slowed in the U.S. since the spring.

On Monday, Pfizer representatives met with federal health officials to advocate for the potential need for Covid boosters, as the pharmaceutical company prepares to seek U.S. authorization for a third dose of its current vaccine.

Pfizer announced last week it's also developing a booster shot to combat the highly transmissible delta variant — now the dominant strain of the virus in the U.S. — stating it's beginning to see waning immunity from its two-shot vaccine developed with German partner BioNTech.

However, the Centers for Disease Control and Prevention and the Food and Drug Administration released a joint statement rebuking Pfizer's push for a third dose, saying fully vaccinated Americans do not need booster shots at this time.

Officials' talk with Pfizer was mostly "a courtesy meeting," Fauci, the head of the National Institute of Allergy and Infectious Diseases, also told CNBC on Tuesday. He said the real question right now is how long protection from the vaccines lasts and at what level of protection, a view echoed by other health experts. 

Former Obama administration official Dr. Kavita Patel told CNBC on Monday, ahead of the Pfizer meeting, that booster shots seem like "an inevitability" due to newer variants, but questioned when that will happen. She also emphasized that the conversation around boosters in the U.S. must take into account the global impacts it will have on the vaccine rollout in other parts of the world.

Dr. Ashish Jha, dean of Brown University's School of Public Health, told CNBC on Friday he has "not seen any evidence, so far, that anybody needs a third shot."

The majority of Americans have been inoculated with Pfizer, followed by the two-shot Moderna vaccine and the single-shot Johnson & Johnson course, according to CDC data. More than 184 million people in the U.S., or 55.5% of the population, have received at least one shot. Nearly 160 million people, or 48% of the population, have been fully vaccinated.

Fauci also told CNBC on Tuesday that he would be "astounded" if the coronavirus vaccines from Pfizer, Moderna and J&J don't get full approval from U.S. drug regulators. Those three vaccines are the only ones cleared by the FDA in the U.S., and their approval was for emergency use authorization.