A decision not to recommend third-shot booster vaccinations for most Americans is “not the end of the story”, White House chief medical adviser Dr Anthony Fauci insisted on Sunday, two days after a scientific panel appeared to turn the Biden administration’s plan for combating coronavirus on its head.

Fauci also said he did not believe a million coronavirus deaths in the US was an inevitability, despite the Delta variant-fuelled surge that last week brought the grim milestone of one in 500 Americans having fallen victim to the pandemic.

The near-unanimous vote on Friday by scientific advisers to the US Food and Drug Administration (FDA) to recommend against a routine third shot of the Pfizer vaccine was seen as a rebuke to Joe Biden, who announced the “third jab strategy” as a main plank of his six-pronged anti-Covid plan.

“I don’t think they made a mistake,” Fauci told CNN’s State of the Union, “but people need to realize that data is coming in, literally on a daily and weekly basis, and they’re going to continue to look at this literally in real time.

“It is entirely conceivable and maybe likely that ultimately the proper regimen for protection, optimal protection and durability of protection would be more than just the prime and the boost followed by three to four weeks, that it might actually entail a third boost.

“… I think people need to understand that this is not the end of the story.”

Studies have shown that most vaccinated Americans want a booster shot. The FDA panel did recommend providing them for those over 65 and at high risk of contracting severe Covid-19. But experts are divided on the benefits of Biden’s proposal for a third shot for the general population.

While the FDA panel’s 16-2 vote is not binding, the Centers for Disease Control and Prevention (CDC) will consider it before making a final decision.

In July, Fauci said he did not believe a third booster was immediately necessary. Earlier this month, he appeared to be leaning towards it.

“Their decision, which I respect, is to go the way we just said, with some limitations on it,” he said on Sunday. “Remembering that data keeps coming in on a weekly basis, we’re going to likely see an evolution of this decision.”

Defending Biden, Fauci said the president had always been “very clear” that the booster shot strategy depended on evaluation by medical experts.

“While we said we are planning to do this, it was always said in his official statements, in the official written statement from all of us, including the FDA and the CDC, that [it] was pending and on the condition of the examination of all of the data by the FDA.

“It was always pending the evaluation of all of the totality of the data from the US, from Israel, and any bit of data that we could get. They did that in the proper deliberative process and they came up with a recommendation which I think is a good recommendation.”

Fauci said data was expected in the “next couple to three weeks” to enable the FDA to evaluate booster shots for the Moderna and Johnson & Johnson vaccines, both of which are currently administered under emergency use authorisation.

With the death toll in the US now past 670,000, according to the CDC, Fauci was asked about fears it could soon reach a million.

“I don’t believe that that is something that is an inevitability,” he said.

“With our vaccines, which are highly efficacious and effective in the real world and safe, if we get the overwhelming proportion of our population vaccinated, we’re not going to see that at all.

“There are 70m people who are eligible to be vaccinated who have not yet gotten vaccinated. If we can get most of those people vaccinated, the overwhelming majority, we will not see the kinds of deaths that you just mentioned.”

Dr Francis Collins, director of the National Institutes of Health (NIH) told CBS’s Face the Nation he believed approval of a booster shot for the general population was still likely, and that he accepted people were “confused” by the mixed messages from the White House and medical experts.

“It was very significant that the FDA advisory committee voted unanimously in favor of offering boosters to people 65 and over and to others who have high-risk exposures like healthcare professionals, so we’re starting down that path,” he said.

“Some of the data we’re seeing coming in, especially from Israel, tells me that it’s likely that they will get to that point. I know people were confused about different messages but this is the way it ought to be, science sort of playing out in a very transparent way, looking at the data coming from multiple places, our country, other countries, and trying to make the best decision for right now. That’s what they did.”

Collins also said the “high risk” group identified by the FDA committee could potentially include professions such as teachers in regular contact with children under 12 who are ineligible for vaccinations.

“Watch this space, because the CDC advisory committee on immunisation practices will be meeting on Wednesday and Thursday,” he said. “That’s going to be a very important thing for them to wrestle with what exactly is included in that group of people with high exposure.”