Dr. Scott Gottlieb told CNBC the U.S. will still have to experience “the hardest stretch” of the coronavirus pandemic without the benefits of a vaccine, despite the positive news earlier Monday from Pfizer.

Gottlieb, a former U.S. Food and Drug Administration commissioner in the Trump administration, is a member of Pfizer’s board of directors.

“The vaccine is really a 2021 event in terms of when it’s going to provide protective immunity to that initial tranche” of recipients, Gottlieb said on “Squawk Box,” shortly after the Pfizer announcement. “Then in terms of when it would be widely available, I think the hope still is … you could have a vaccine broadly maybe the end of the second quarter, maybe into the third quarter.”

U.S. pharmaceutical giant Pfizer announced that the vaccine it’s developing with German firm BioNTech is more than 90% effective in preventing Covid-19 for those who had no evidence of previously being infected.

“I think we need to remember that we have perhaps a brief, but very hard stretch, ahead of us,” Gottlieb said as the U.S. has set a series of all-time highs for new daily Covid-19 cases in recent days. He told CNBC on Friday he believes the cases may “explode in several weeks.”

However, Gottlieb said Monday “We ought to take this positive news and recognize there may be a much better future ahead of us. … We may be available to have a vaccine broadly available at some point in 2021 and do everything we can to continue to protect people who are vulnerable to this virus.”

Disclosure: Scott Gottlieb is a CNBC contributor and is a member of the boards of Pfizer, genetic testing start-up Tempus and biotech company Illumina. Gottlieb also serves as co-chair of Norwegian Cruise Line Holdings′ and Royal Caribbean’s “Healthy Sail Panel.” 

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