The US is likely to see an increase in Covid cases like that in Europe and the UK thanks to the BA.2 virus subvariant but not a dangerous surge, Anthony Fauci said on Sunday.

Joe Biden’s chief medical adviser also said the US was “clearly going in the right direction” on the coronavirus pandemic.

BA.2, Fauci told ABC’s This Week, “has a degree of transmission advantage over the original Omicron [variant], but not multifold advantage. So, it’s about 50% to 60% or so more transmissible, which means ultimately it might take over as a dominant variant.

“Clearly, throughout the world it’s about 80-plus percent, 85% of the isolate. In the United States, it’s still somewhere around 30%.

“So it does have an increased transmission capability. However, when you look at the cases, they do not appear to be any more severe and they do not appear to evade immune responses either from vaccines or prior infection.

“So the bottom line is we likely will see an uptick in cases as we’ve seen in the European countries, particularly the UK, where … they have BA.2. They have a relaxation of some restrictions such as indoor masking and there’s a waning of immunity.

“Hopefully, we won’t see a surge. I don’t think we will. The easiest way to prevent that is to continue to get people vaccinated. And for those who have been vaccinated, to continue to get them boosted.”

Fauci said he did not see any reason to reimpose public health restrictions relaxed under a federal approach meant to focus on areas with pressure on hospital systems.

“But you always have to have the flexibility,” he said.

“Remember, when the [Centers for Disease Control and Prevention] came out with the modification of their metrics, which would lead to the guidelines of what regions or counties in the country should have a masking indoors, they made it very clear that … if we do see a significant surge, particularly one that might result in increased hospitalisations, we have to be prepared to pivot and perhaps reinstitute some of those restrictions.

“But right now, at this point, I don’t see that.”

More than 970,000 people have died of Covid-19 in the US. Fauci said vaccination and booster rates still needed to be improved and said Congress should build-up supplies of anti-virals, tests and booster shots.

“We just can’t stand still,” he said, “particularly as we appear to be in somewhat of a lull … where cases continue to come down, deaths continue to come down and hospitalisations [too].

“That’s no time at all to declare victory because this virus has fooled us before, and we really must be prepared for the possibility that we might get another variant and we don’t want to be caught flatfooted on that.”

Fauci, 81 and the director of the National Institute of Allergy and Infectious Disease, has served seven presidents since 1984. He has said he will consider retiring when the pandemic is done.

Asked if he was any nearer such a decision, he told ABC: “I’m not so sure. I want to make sure we’re really out of this before I really seriously consider doing anything different.

“We’re still in this. We have a way to go. I think we’re clearly going in the right direction. Hope we stay that way.”