As Covid-19 cases rise again in the United States, health experts are urging Americans to get vaccine booster shots and warning of a potentially serious winter surge.

5 key considerations for the expanded booster shot rollout

Covid-19 cases surge in some areas of the U.S.

The average daily number of U.S. Covid-19 cases has increased by 29% in the last two weeks, according to data compiled by the New York Times. But some parts of the country have seen even greater increases.

In Minnesota, for instance, Covid-19 cases have increased 47% over the past week, and hospital admissions have increased 24%. The biggest increases have occurred among those ages 30 to 49, CBS News reports.

"I have never seen so many people on a ventilator at one time," Joshua Huelster, a critical care physician at Abbott Northwestern Hospital, said, adding that the "vast majority of patients that we see in the ICU are not vaccinated."

Compared to the beginning of November, hospitals in Minnesota are now caring for 40% more Covid-19 patients, and the state last week had the highest rate of Covid-19 cases per 100,000 residents in the country.

Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy, said if someone had predicted Minnesota would have the most Covid-19 cases per capita in the country months ago, "no one would have believed it."

Meanwhile, in Detroit, new Covid-19 cases have increased to 3,858 in the past 14 days, up from 2,322 in the two weeks prior, according to the city's health officer, Denise Fair Razo.

"We're in Michigan so we're not finding ourselves spending time outdoors in flip-flops and tank tops," Fair Razo said. "We are indoors and we're frankly becoming a little bit too relaxed. We're no longer wearing our masks. We're no longer washing our hands as frequently as we should. But we know these precautions."

Three states now have hospitals operating under crisis standards of care as a result of Covid-19 surges: Colorado, Idaho, and New Mexico.

"Things are not going well in our hospitals," David Scrase, acting cabinet secretary of the New Mexico Department of Health, said. Last Wednesday, the state reported 1,530 new Covid-19 cases and 539 hospitalizations, and according to Scrase, the state is "facing some very serious problems," particularly with ICU capacity.

"Last week, we had only eight ICU beds, now we're up to 10—still nowhere near enough ICU beds," Scrase said. "What this does mean is someone having a heart attack right now may or may not have access to ICU care in New Mexico, and frankly, as cases start rising again in other states, we may not find a bed there."

Health experts warn of winter surge

As of Sunday, the United States is averaging more than 1,100 Covid-19 deaths per day, roughly the same as this time last year, Politico reports.

"I do think we will see more deaths than we are currently seeing," Eric Toner, a senior scholar at the Johns Hopkins Center for Health Security, said. "People need to be cautious about traveling and getting together."

"People don't realize how high the risk is to transmit the virus to a vulnerable family member," David Rubin, a pediatrician and director of PolicyLab at Children's Hospital of Philadelphia, said. "I don't think there's a sense that anyone is holding back this Thanksgiving. If people were smart, they'd quarantine themselves if they live in a place with high transmission."

Former Surgeon General Jerome Adams in an interview warned there is likely to be a "winter surge" of Covid-19 cases. "It's no longer a matter of if we're going to have a winter surge, it's how bad it's going to be," he said. Adams argued that Americans have become "complacent" during the pandemic and urged caution during the holiday season.

Health officials advocate for booster shots

As cases rise in some parts of the United States, health officials are encouraging Americans to get booster shots of their Covid-19 vaccines, following CDC's approval of booster shots for all Americans ages 18 and older.

As part of the recommendation, CDC said all Americans "may" get a booster shot, while those ages 50 and older "should" get the shot.

This distinction drew some criticism from health experts, who said the phrasing frames booster shots as a "luxury" for younger people rather than a necessity.

"I can tell you that clinicians notice that language and it matters a lot when it comes to what clinicians are recommending to their patients," Leana Wen, an emergency physician and public health professor at George Washington University, said.

"My concern is that, with the messaging so muddled, the booster dose has somehow been framed as a luxury, as something that would be nice to have but it doesn't really matter if you get it. That is not the case," she added.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, urged all Americans to get a booster shot ahead of a potentially "dangerous" winter surge. "Get vaccinated if you're not vaccinated and boostered if you have been vaccinated," Fauci said.

Fauci also said he hopes booster shots will increase the durability of the vaccines so that "you will not necessarily need it" every six months or year. "We would hope—and this is something that we're looking at very carefully—that that third shot with the mRNA not only boosts you way up but increases the durability so that you will not necessarily need it every six months or a year," Fauci said. (Collin, CBS News, 11/19; Keith, FOX9, 11/18; White, Associated Press, 11/18; Deliso, ABC News, 11/18; Vakil, The Hill, 11/20; Doherty, Axios, 11/19; Vakil, The Hill, 11/21; Goldberg, Politico, 11/22; Timsit/Pietsch, Washington Post, 11/22; Neergaard et al., Associated Press, 11/19; Reed, Axios, 11/22; New York Times, 11/22)