Dr. Scott Gottlieb told CNBC on Wednesday that he believes enough Americans are fully vaccinated to delay the risk of the Delta-Covid variant.

“The question is, are there enough unvaccinated people for this to get into the population and spread further? I happen to think it unlikely that this could pose a threat until the fall,” the former Food and Drug Administration commissioner said “Squawk Box”.

Gottlieb’s comments come as speculation mounts that Britain may lift all lockdown measures in England for Jan.

The most severe cases with the Delta variant appear to occur in unvaccinated or only partially vaccinated people, said Gottlieb. “It appears to be a more dangerous variant. However, two doses of the vaccine appear to be very protective.”

“People who are fully vaccinated are, in my opinion, fairly well protected against this new variant based on the evidence available,” added Gottlieb, who headed the FDA in the Trump administration from 2017 to 2019. He now sits on the board of directors at vaccine company Pfizer.

On Tuesday, White House senior medical advisor Dr. Anthony Fauci, the importance of fully vaccinating Americans to protect against the Delta variant. Currently, Fauci accounts for more than 6% of US coronavirus infections that scientists have genetically sequenced.

The delta variant is now becoming the dominant variant in the UK. In the USA and Great Britain, around 53% of adults are now fully vaccinated against Covid. However, Gottlieb said England’s decision to postpone administering the second dose in order to give more people first shots “likely opened the door to this spread a little further”.

At a White House briefing Tuesday, Fauci cited examples of Covid vaccines from Pfizer and AstraZeneca – which are used in the UK but not the US – and said they were about 33% at protecting against the Delta after a dose Variant effective. For Pfizer, effectiveness rose to 88% after the second vaccination, Fauci said, while AstraZeneca’s vaccine was 60% effective, according to the National Institutes of Health.

“It seems that two doses of the vaccine against these variants are more important than against the old strain of the virus,” said Gottlieb.

Despite advances in vaccination in the United States, Gottlieb admitted that there could be worrying situations in the country with the Delta variant. “If you have a community that has a lot of unvaccinated people and you have a super sprawling event with Delta … you could get an outbreak here.”

Covid cases in the US continue to decline. According to a CNBC analysis of the Johns Hopkins University data, the seven-day average of new coronavirus infections daily is around 14,400. That is around 17% less than a week ago. It also means a decrease of over 60% from about a month ago. The highest single day of new cases in the U.S. was 300,462 on Jan. 2.

Disclosure: Scott Gottlieb is a CNBC employee and a member of the board of directors of Pfizer, genetic testing startup Tempus, health technology company Aetion, and biotechnology company Illumina. He is also co-chair of the Healthy Sail Panel of Norwegian Cruise Line Holdings and Royal Caribbean.