(CNN) – Mass vaccinations and natural protection from those already infected are likely to prevent the fourth wave of COVID-19 in the United States, said Dr. Scott Gottlieb, former commissioner of the Food and Drug Administration, Sunday.

“We’re talking about some form of protective immunity in about 55% of the population,” said Gottlieb at CBS’s Face the Nation. “There’s enough bottlenecks in here that I don’t think you’ll see a fourth spike.”

About 81 million people have received at least one dose of the vaccine, a number that is increasing significantly every day. In addition, about 29 million people have tested positive for the virus and recovered, and tens of millions more have had COVID-19 without a positive test result and have natural immunity.

However, the US will continue to see COVID-19 cases and deaths, Gottlieb warned, especially as a dangerous variant that was first identified in the UK is spreading.

“I think what you can see is a stagnation for a period of time before we continue the decline – in large part because (the British variant) is becoming more prevalent, in large part because we pulled back too quickly, in regards to removing our masks and lifting the mitigation,” he said.

Gottlieb also warned that the emergence of a virus variant could change the trajectory of the nation.

“The only thing that could be a real game changer here is if you have a variant that penetrates prior immunity, meaning it re-infects people who are already infected or who have been vaccinated,” he said.

Gottlieb’s comments come as the number of US COVID-19 cases has stabilized at around 50,000 new cases per day over the past seven days. Some experts have warned of another surge as the US races to vaccinate and stay ahead of variants.

“This is a time of crisis,” said Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, told CNN Saturday. “This will be our toughest period at the moment in terms of seeing who wins.”

With about a quarter of all Americans having received at least one dose of the COVID-19 vaccine – and about 13% were fully vaccinated – Doubling current security measures is what could help curb another surge, experts repeatedly stress.

“If we can last another month, another six weeks, it will make a big difference,” added Hotez.

However, air travel reach pandemic era records and the spring break crowd was swelling. In Miami Beach, officials declared a state of emergency Saturday in response to the crowd, said the mayor had “more than we can handle.”

And at least a dozen governors and many local leaders have them restrictions are reduced this month, while some have get rid of the mask mandate at all.

Michigan cases and hospitalizations are increasing

In Michigan, where the governor announced a series of restrictions that were relaxed earlier this month, said the current officials the state could potentially be at the start of another wave.

“Our progress with COVID-19 is fragile,” said Dr. Joneigh Khaldun, chief medical executive for the state of Michigan, in a news conference Friday. “While we are making great progress with our vaccination efforts and a lot of people are doing the right thing wearing masks and not gathering in large groups, what we see now are very concerning data showing that we are going in the wrong direction.”

The rate of cases has risen over the past month, Khaldun said, and increased by 77% since mid-February.

The percentage of the state’s COVID-19 tests positive has also jumped 177% since mid-February, Khaldun said. And the hospitalization rate has also increased over the past two weeks, added Khaldun.

Michigan has also reported the second-highest number of cases of variant B.1.1.7 in the country, after Florida, according to to CDC data.

“This is very worrying,” said Dr. Rob Davidson, an emergency room doctor in the state, told CNN Saturday. “We know in the past, cases increased, then hospitalized, then deaths followed.”

Davidson told CNN he is even more worried now that the variant is in circulation, and hopes the country can make enough progress to protect the population.

“It remains to be seen,” said Davidson. “We prefer not to wait and find out. We prefer to ask people to cover up, keep our distance and lower those numbers.”

Political gap in vaccination

More than 44 million Americans have been fully vaccinated, according to CDC data.

The growing numbers are encouraging, but experts say the country still has a long way to go to reach the levels needed to contain the spread of the virus – and must overcoming vaccine doubts as well as political division that gets in the way.

In Missouri, Governor Mike Parson said Friday that while he encourages everyone to get vaccinated and thinks it’s the right thing to do, he knows there will be “some people” who won’t take the vaccine, “and they have the right to do that.”

“We have to do a better job of making sure everyone understands the importance of vaccines, while maintaining respect for people who don’t want to use vaccines, and it will be a challenge to see how many people we have doable, but we will. do all we can, “said the governor.

A recent CNN poll conducted by SSRS, showing that 92% of Democrats say they have had a dose of the vaccine or plan to get it, that’s down to 50% among Republicans.

Former head of Operation Warp Speed, Moncef Slaoui, said he was deeply concerned about vaccine doubts being fueled by politics.

“I am very concerned that, for the sake of political motivation, people decide to really harm themselves and those around them by refusing to be vaccinated,” Slaoui said in an interview broadcast Sunday on Face the Nation.

Slaoui also rejected President Joe Biden’s criticism of the Trump Administration’s vaccine plan, defending last year’s Operation Warp Speed ​​efforts.

“I think we have a plan, and in fact, 90% of what is happening now is the plan we have,” Slaoui said.

“We contract specifically for 100 million doses of the vaccine, but also enter into a contractual option to get more vaccines, once we know they are effective. The plan is to order more vaccines when we know they are more effective,” he said. “What happened was, frankly, what the plan was – basically, what was the plan.”

CNN’s Pete Muntean, Carma Hassan, Mirna Alsharif and Alec Snyder contributed to this report.