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As most states begin to move forward with measures to reopen their economies following strict lockdowns aimed at slowing the spread of the coronavirus, some governors and big-city mayors are now saying the restrictions will not fully be lifted until a vaccine or treatment for the disease is available — a timeline that could take a year or more.

The leaders' comments indicate Americans could be living with orders restricting personal and economic activity for much longer than many anticipate.

They also come after President Trump said Friday that the U.S. will reopen "vaccine or no vaccine," and told governors in a call Monday that the federal government "will step in if we see something going wrong, or if we disagree" with how states are lifting their lockdown orders aimed at preventing the virus' spread.

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New Jersey Gov. Phil Murphy was the latest of the state executives to make such comments in a press conference on Monday.

"You, too, should expect to continue with this for the foreseeable future," Murphy said of the state's coronavirus restrictions, as he outlined when workers might be able to get back to their offices.

He continued: "Until either a proven vaccine is in our midst or proven therapeutics are widely available, we cannot firmly enter the new normal, which eventually awaits us when life will once again return to all of our workplaces, downtowns and main streets. Most importantly, we will continue to be guided by the principle that public health creates economic health. And if we begin to see a backslide in public health, we will have to also pull back on the reins of our restart."

Michigan Gov. Gretchen Whitmer said that crowds would not be able to gather for professional or college sports in her state until a vaccine is available or there's a rigorous testing regime in place with signs of herd immunity in the population.

"We're gonna be in a new normal for quite a while. And it doesn't mean that sports is over," Whitmer said in a press conference Friday, mentioning a plan being pursued by the MLB to play a shortened season with no fans present.

"We need a vaccine, and we need to have mass quantities available," she continued. "Or we need to be able to test and be able to acknowledge that we've got some immunity that's built up. We're not there yet and until that happens I think all the organizers of these leagues understand how important it is that we act responsibly here."

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Los Angeles Mayor Eric Garcetti made similar comments in an interview on ABC's "Good Morning America" last week.

"We have to all recognize that we're not moving beyond COVID-19, we're learning to live with it," Garcetti said. "There's no so-called 'open state' or 'open country' that doesn't continue to have health orders telling us to cover our faces, physical distance and to tell people that you're safest working from and staying at home."

Garcetti continued to say that his city would not be fully open until there is a vaccine available, noting that he does not plan to have a full reopening of the city's schools in the fall.

"We've never been fully closed, we won't be completely open until we have a cure, but I do believe that we can take steps," he said.

Illinois Gov. J.B. Pritzker gave an even more dire warning during the briefing on his state's reopening plan earlier this month, according to the Chicago Sun-Times.

"I know that we all have a passionate desire to return to the sense of normalcy that we felt before the world knew of COVID-19. Here’s the truth. And I don’t like it any more than you do," he said. "Until we have a vaccine, or an effective treatment, or enough widespread immunity that new cases fail to materialize, the option of returning to normalcy doesn’t exist."

Oklahoma City Mayor David Holt, a Republican, told CNN's "New Day" late last month that he has qualms about opening up his city any time before there is a vaccine or medicine available to combat the coronavirus.

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"Until there is a vaccine or a proven treatment, I am not going to be comfortable about this transition," Holt said. "On the other hand, we can't shelter in place forever."

Holt said that despite a reopening date set by Oklahoma Gov. Kevin Stitt, that he would add "conditions" that must be followed in his city, including social distancing measures in restaurants and hairstylists being required to wear masks.

The Trump administration is backing efforts to speed along a potential coronavirus vaccine, and although the president has optimistically said one might be ready by the end of the year, medical experts like National Institute of Allergy and Infectious Diseases Director Dr. Anthony Fauci have said it is not particularly likely there will be one available before 2021.

While a vaccine or an effective treatment for the coronavirus is the holy grail for the fight against the disease – Sen. Lamar Alexander, R-Tenn., called them the "ultimate solution" at a Senate Health Committee hearing last week – Fauci and others have made clear they are not the only way to get things going again.

After a comment Fauci made during the hearing about vaccine development and reopening schools was apparently misinterpreted, Alexander gave Fauci a chance to clarify.

"What I thought I heard was that Dr. Fauci said that vaccines are coming as fast as they ever have but it will be later in the year at the earliest before we see that there's some treatment ... but that that doesn't mean that you shouldn't go back to school. That would be more our testing strategy," Alexander said, before asking Fauci to confirm his understanding.

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"What I was referring to was going back to school would be more in the realm of knowing the landscape of infection with regard to testing," Fauci said, agreeing with Alexander before noting that the level of the coronavirus outbreak in individual areas would be more important. "I did not mean to imply at all any relationship between the availability of a vaccine and treatment and our ability to go back to school."

Of course, states like New Jersey are not completely foreclosing reopening measures until a vaccine is made available. Murphy in the same press conference also announced the loosening of multiple elements of the state's coronavirus restrictions — including letting golfers tee off in foursomes instead of just in twosomes.

But the prospect that people may be working from home, wearing masks to the grocery store or unable to gather at sporting events or concerts for up to a year or even more in some states is more sobering confirmation that the effects of the coronavirus pandemic could very well linger well past the upcoming presidential election.

"While we are not nearly out of the woods yet, and thousands of our fellow New Jerseyans remain in the hospital battling COVID-19, as you can see we are moving forward carefully, methodically and responsibly," Murphy said.

Visitors, wearing face masks, enter the Disneyland theme park in Shanghai as it reopened, Monday, May 11, 2020. Visits will be limited initially and must be booked in advance, and the company said it will increase cleaning and require social distancing in lines for the various attractions.(AP Photo/Sam McNeil)

Visitors, wearing face masks, enter the Disneyland theme park in Shanghai as it reopened, Monday, May 11, 2020. Visits will be limited initially and must be booked in advance, and the company said it will increase cleaning and require social distancing in lines for the various attractions.(AP Photo/Sam McNeil)

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He compared the "new normal" Americans face at the end of the pandemic to the reality of security checkpoints in airports after 9/11, which is something that now seems routine to Americans traveling through airports.

There is still some hope of a vaccine to come in 2020, however, even if the chances are slim for such an unprecedented accomplishment.

The biotech company Moderna announced Monday that it had seen some positive progress in trials for its vaccine, and a Johns Hopkins health expert said Sunday on NBC's "Meet the Press" that a vaccine could be available by the end of the year — though he cautioned not to "bank on it."

"Given that there are now 110 vaccine projects going on around the world that all the major vaccine companies in the world are working on this in some way, and given that Tony Fauci and Moncef Slaoui are now leading figures in the U.S. in this project and they both believe it’s possible, I think it is possible,” Dr. Tom Inglesby, the director of the Center for Health Security of the Johns Hopkins Bloomberg School of Public Health, said.

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He continued: “But, everything would have to break in the right way, and there are many ways that it might not work. So, I don’t think we should bank on it."

Sen. Alexander, in a Senate Health Committee hearing last week, mentioned one way the government might be able to speed up the production of a vaccine that shows signs it might work while also saying that increased testing measures could allow life to get back to normal in the meantime. He said that the government might make an effort to mass-manufacture a vaccine before it’s been proven to work so it can be quickly distributed once it’s officially approved.

“Those vaccines, those treatments, are the ultimate solution,” Alexander said. “But until we have them, all roads back to work and school go through testing."

Fox News' Chris Ciaccia and Bradford Betz contributed to this report.