WASHINGTON D.C (KPIX 5) — U.S. health officials made what had been rumored official Wednesday, announcing that vaccine booster shots will start rolling out in September. The FDA still has to sign off on the action, but health officials started making their pitch immediately.

”All of this supports the use of a third booster mRNA immunization,” said Dr. Anthony Fauci, describing the evidence that led to the White House announcement.

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It is a two-fold problem, they say; Coronavirus vaccines, like all vaccines, lose their strength as the months pass, and in this case, they’re fighting a stronger opponent.

“Recent data makes clear that protection against mild and moderate disease has decreased over time,” explained U.S. Surgeon General Dr. Vivek H. Murthy. “This is likely due to both waning immunity, and the strength of the widespread delta variant.”

The distinction made on disease severity is an important one, as health officials have not said that vaccines lose their effectiveness against severe illness.

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“So, depending on how you look at things, the data published today is still reassuring,” said Dr. Jorge Salinas of Stanford Healthcare.

It will be undeniably difficult to strike a balance between encouraging booster shots and maintaining confidence in the current vaccines. The White House team admitted today that they don’t have all the answers, and many doctors have their own questions.

“Most people would like to see the data on which this was based,” said UCSF’s Dr. Peter Chin-Hong. “At the end of the day, is it going to be harmful? No. Is it going to be effective? Possibly, probably more effective than some groups.”

The booster rollout will officially start September 20th, with more research on the vaccines – and boosters – arriving between now and then.

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“I think this is a very tough decision,” Salinas says. “And I’m hopeful and optimistic that the scientists advising the FDA and CDC will provide more nuance to this announcement.”