Bloomberg Law
Sept. 22, 2021, 7:39 PM

MRNA Vaccines Will Require 3 Doses From Start, Fauci Predicts

Jeannie Baumann
Jeannie Baumann

Future administration of mRNA vaccines like Pfizer-BioNTech SE and Moderna Inc.'s will likely require three doses from the start, instead of two doses plus a booster, Anthony S. Fauci said.

If implemented as the top infectious disease expert predicted, the third shot would become part of the primary series, potentially changing the vaccine label and plan for administering shots altogether.

“It should be a proper one from the get-go—three shots. And the reason we didn’t know that right away was because we were dealing with such an emergency situation that we needed to show the vaccine was effective and safe, which we did with the two shots. And we needed to implement that to save lives, which we have, probably already saved millions of lives,” Fauci said Wednesday at the Boston Globe Summit. “So what I predict—and we’ll have to wait to see—but I believe this is going to happen is” the correct regimen going forward will be three shots.

That vaccine regimen would then be two initial doses followed by a third dose a few months later. For Johnson & Johnson’s one-shot vaccine, the first dose would be followed by a second shot a few months later, he said.

Fauci, the White House chief medical adviser for Covid-19 and director of the National Institute for Allergy and Infectious Diseases, made his remarks as the Centers for Disease Control and Prevention’s vaccine advisory committee held the first of its two-day meeting on whether to recommend boosters of Pfizer Inc.‘s vaccine.

The CDC advisory panel remained in a bit of a holding pattern as the Food and Drug Administration had yet to authorize the boosters when the meeting began. The FDA’s advisory panel Sept. 17 voted against Pfizer’s application proposing boosters for everyone 16 and older in favor of a narrower approach, out of concern that the data to support such a broad application was thin. The FDA’s decision will likely come Wednesday.

Fauci continued to support the need for boosters, citing data coming out of U.S. studies as well as data from Israel.

“The data are very clear. When the FDA sees the data, which they are seeing it soon, I believe they will come to the same conclusion,” he said at the summit. “There’s no doubt that in the United States those who’ve been vaccinated several months ago are having a diminution of protection against infection, the beginning of the hint of a diminution of protection against severe disease.”

The data from Israel was “crystal clear” in demonstrating a substantial diminution in protection against infection. “And when they implemented their booster program, it’s unequivocal that boosters have increased the degree of protection, over and above [what] the protection was with just the original two doses,” Fauci said. “So boosters unequivocally work and dramatically increase the level of protection. Those are real data. I have seen them, and that’s the reason why I feel we should proceed with the booster program.”

At the same time, the World Health Organization has criticized plans from wealthier nations to roll out third doses, arguing those doses should instead be redirected to lower- and middle-income countries with less access to vaccine supply. Fauci said he agreed with the WHO on the need to be attentive to equity, but he said the U.S. can simultaneously distribute boosters while taking care of vaccinating the world.

“With regard to [what] the WHO was saying, it is understandable because they appropriately are interested in the equity, getting vaccines to the rest of the world. I am very much in favor of that,” he said.

Fauci’s comments come as President Joe Biden hosted a virtual Covid-19 summit during which he called on other nations to help expand the supply of Covid-19 vaccines and treatments. The U.S. will buy another 500 million doses of the Pfizer-BioNTech vaccine for donation abroad, bringing the nation’s total planned donation to more than 1.1 billion doses. The U.S. has provided more than 157 million vaccine doses to over 100 countries as of Sept. 21, according to the State Department.

“We can do both. We can provide boosters to those who need it as the efficacy wanes of the vaccine, particularly in the context of the Delta variant. But we also can and are providing a considerable amount of doses of vaccine to lower- and middle-income countries.”

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To contact the editors responsible for this story: Alexis Kramer at; Karl Hardy at