Dr. Fauci says 'a booster isn't a luxury' — think of it as the final step in your COVID-19 vaccine regimen

• Dr. Fauci predicts that Pfizer and Moderna COVID-19 vaccines may, one day, be considered three shot vaccinations.
• That's because the immune system learns better when shots are spaced several months apart.

Dr. Fauci wants every adult who's been fully vaccinated with Pfizer or Moderna to know — it's OK to go get a booster, once you're eligible.

In fact, the director of the National Institute of Allergy and Infectious Diseases suspects that one day, the normal, full dosing schedule for Pfizer and Moderna COVID-19 vaccines will be three shots, with the last one given at least six months after the second.

"A booster isn't a luxury, a booster isn't an add on, and a booster is part of what the original regimen should be," Fauci told reporter Helen Branswell during the 2021 STAT Summit on Tuesday.

Though he admitted that "no one knows," yet, exactly what the ideal interval for dosing these new vaccines will be, he was glad to venture an educated guess.

"I happen to believe, as an immunologist and an infectious disease person, that a third shot boost for an mRNA is likely — should be part of the actual, standard regimen," Fauci said.

It goes along with what he told Insider on Monday, that boosters should be offered to all US adults, without exception — contrary to the CDC's current position that boosts should be saved for Johnson & Johnson recipients, as well as older adults, those with preconditions, or vulnerable people who live and work at high exposure to the coronavirus.

Many immunologists say this idea makes sense, from a biological perspective. The body needs several months to mount a truly robust response to a vaccination. During that time, T cells and B cells cement their memory of how to fight off the coronavirus, in case a person should encounter it again.

"We know, again, from immunology that goes back way back, the longer you wait to give the boost, the stronger the response will be," immunology expert Dr. James Hildreth, president of Meharry Medical College, recently told Insider. "That's why there is a recommendation that if you have COVID-19, you have [monoclonal] antibodies, it might be wise to wait a while to let the antibody levels drop a bit so you get the maximum benefit of the vaccine."

Some experts stress that, even without that extra benefit of time, two initial doses spaced several weeks apart may be enough protection against severe disease for most young adults, indefinitely.

But by boosting people at six months out, "you're going to qualitatively and quantitatively have a different immunological phenomenon," Fauci said. "We will have given the B cell memory and T cell memory enough time to have affinity maturation."

He suspects there's a "reasonable" possibility that because of that maturation, "we're not going to see an absolute need to reboost every several months" once a third dose is given.