• The CDC's new outdoor Covid mask policy is "a step in the right direction, but it's relatively confusing," Dr. Scott Gottlieb told CNBC on Wednesday.
• The former FDA chief said the country's "public health goal" needs to focus on preventing superspreading events and protecting vulnerable Americans.
• Gottlieb said he's concerned people could "stop listening" to the CDC without a change in approach.

Dr. Scott Gottlieb said Wednesday the Centers for Disease Control and Prevention needs to more nimbly update its coronavirus guidelines as the pandemic situation improves.

A day earlier, the U.S. public health agency issued new, relaxed guidance on the need for fully vaccinated people to wear masks outdoors.

"The guidance that CDC put out, I think, is a step in the right direction, but it's relatively confusing," Gottlieb, a former Food and Drug Administration commissioner, said on CNBC's "Squawk Box." "It's not very clear in terms of what they're prescribing. I think we need simpler rules if we're going to be prescribing something over society."

People who have been fully vaccinated — considered two weeks after their final dose — can safely exercise and go to small gatherings outdoors without wearing a face mask, according to the new CDC guidance. However, the agency recommends fully vaccinated people keep wearing masks if they attend an outdoor event that's crowded, such as a parade, a sports game or concert.

The CDC also said it's safe for unvaccinated Americans to forgo wearing a mask while attending a small outdoor gathering with friends and family if those other attendees are fully vaccinated.

The CDC needs to better define what it hopes to achieve at this stage in the pandemic, when national infection levels are dropping and more than 54% of U.S. adults have received at least one vaccine dose, said Gottlieb, who sits on the board of Covid vaccine maker Pfizer.

"I think the public health goal should be to try to protect vulnerable populations in congregate settings, so continue to focus on nursing homes, day-care settings where small children are, and try to prevent large outbreaks, try to prevent superspreading events," he said.

Roughly 68% of U.S. residents age 65 and up have been fully vaccinated, according to CDC data, while about 82% of that most-vulnerable population has received at least one dose.

"We're not going to be able to prevent a single introduction, where a single person transfers a virus to a single individual. But in a backdrop of declining [coronavirus] prevalence, rising vaccination rates and more of the vulnerable Americans protected through vaccination, we need to lean forward," said Gottlieb, who led the FDA from 2017 to 2019 in the Trump administration.

The seven-day average of new coronavirus cases per day in the U.S. is roughly 53,800, according to a CNBC analysis of Johns Hopkins University data. That's down 17% from one week ago.

The U.S. is seeing an average of 676 new Covid deaths per day, based on a seven-day moving average, according to CNBC's analysis of Johns Hopkins data. That represents a 6% decline from one week ago.

Gottlieb, who earlier this week called for the end of outdoor mask requirements, said he was concerned about the implications of the CDC continuing to be overly cautious with its guidance.

"I think the risk to CDC as an institution — it's an extremely important institution — is that they lose relevancy, that people stop listening to them," he said, while issuing a broader warning to those in the U.S. who are setting coronavirus policies.

"The challenge is, if we don't lift these restrictions with the same speed and the same efficiency that we imposed them, we lose credibility as public health officials to reimpose them in the future because more of the population will be worried that these are a one-way street," he said.

The CDC did not immediately respond to CNBC's request for comment.

Disclosure: Scott Gottlieb is a CNBC contributor and is a member of the boards of Pfizer, genetic testing start-up Tempus, health-care tech company Aetion Inc. and biotech company Illumina. He also serves as co-chair of Norwegian Cruise Line Holdings' and Royal Caribbean's "Healthy Sail Panel."