CNN  — 

Booster doses of Moderna’s Covid-19 vaccine may be delayed from rolling out the week of September 20 as planned, Dr. Anthony Fauci said Sunday.

Fauci, President Joe Biden’s chief medical adviser, said that while the administration’s plan had been to roll out booster doses of both Pfizer and Moderna at the same time, that may not happen.

Fauci said vaccine maker Pfizer has submitted its information to the US Food and Drug Administration and “things look like they’re ready to go,” Fauci told CNN’s Jim Acosta.

He said Moderna might be a little bit behind that, and if it is, rather than seeing a simultaneous rollout of both products, Moderna could be rolled out a week or two later.

“I don’t think that is a major issue there, but we would have liked to have seen it happen all together, simultaneously. But ultimately the plan will be implemented, as was put forth,” Fauci said.

Fauci said the plan is contingent first on the companies submitting the appropriate data to the FDA, and second, getting FDA approval and then a recommendation from the US Centers for Disease Control and Prevention’s vaccine advisers.

Fauci said ultimately, it may turn out the proper Covid-19 immunization regimen is three doses.

“What we’re observing now – not only here in the United States but in other countries, including Israel and the UK – (is) that the durability of the protection tends to wane, particularly in the context of the Delta variant,” Fauci told CNN.

He explained how such waning can lead to both breakthrough infections and breakthrough infections that lead to hospitalizations.

“You look at the evidence from the cohorts here in the United States, there’s no doubt that there is a diminution in the efficacy of the vaccine against infection, namely symptomatic infection. There’s a slight suggestion in a couple of the cohorts that it also is true for a diminution of protection against hospitalization – not profound, but the suggestion when you look at the data is there,” he said.

“However, when you look at the Israeli data, and they are about a month or so ahead of us in every aspect of this – vaccinations, boosters, etc. – the data from the Israeli studies are that there’s a rather substantial diminution in protection against infection and an unquestionable diminution in the protection against hospitalization.”

Fauci said the good news is that data from Israel shows booster doses offer “profound” protection against infection and hospitalization.

“Importantly, their data also show that when you give those boosters you reconstitute, to an even higher level than before, the protection against both infection and hospitalization,” Fauci said. “The boosters really jack up the response very, very high, and we hope that that response would be durable.”