(CNN) While the rate of Covid-19 infections nationwide is slowing, health care systems in some parts of the country are struggling with hospital wings still packed with patients.
Montana, for instance, is facing new highs this week in coronavirus hospitalizations, with 533 Covid-19 patients in hospitals as of Wednesday, according to the US Department of Health and Human Services. This eclipses the high set in November, before vaccines were readily available, according to HHS and data from the Covid Tracking Project.
The percentages of ICU beds used for Covid-19 patients in Montana, along with neighboring Idaho and Wyoming, are among the highest in the country, HHS data showed.
This comes as vaccine advisers to the US Food and Drug Administration are meeting Thursday to discuss whether to authorize boosters of Moderna's coronavirus vaccine for some adults, with a recommendation vote scheduled for the afternoon.
But as Covid-19 hot spots like those in the Rockies emerge from the surge driven by the more infectious Delta variant, many doctors and officials are more focused on the millions of Americans who still aren't vaccinated at all -- and they say the pandemic will simmer as long as so many remain unvaccinated.
"Sadly, today I'm here to tell you that we've lost the war. That Covid is here to stay," Dr. Steven Nemerson, chief clinical officer with Saint Alphonsus Health System in Boise, Idaho, said Wednesday. "And the reason it is here to stay is because we cannot vaccinate enough of the public to fully eradicate the disease."
Idaho has been slammed by the pandemic over the last two months. Coroners and funeral homes reported running out of storage space for bodies last month due to the increase in deaths.
The day that the first vaccine was released last December was the pandemic's equivalent of D-Day, Nemerson said, and Covid-19 will be a recurring problem for years to come because the US failed to meet the challenge.
"There are episodes, at least on an annual basis, that we'll have to deal with," Nemerson said Tuesday during a briefing hosted by the state Department of Health and Welfare.
Hospitalizations at Saint Alphonsus have declined recently, Nemerson said, but that's doing little more than giving exhausted health professionals a chance to come up for air, particularly as workers face hostility from some Covid-19 patients and families.
"None of us are superhuman, and we all have a limit to how much work we're able to do, and how much stress and despondency we're able to handle," he said, "and that's compounded by the fact that too many people are coming into our hospitals questioning what we do."
In other parts of the country, some hospitals remain stretched thin. Alabama, Georgia, Kentucky, New Mexico and Texas have 15% or less of their ICU capacity available to Covid-19 and non-Covid-19 patients, according to HHS data.
Idaho and Montana are two of 15 states that have still yet to fully vaccinate at least half of all residents, according to data from the US Centers for Disease Control and Prevention. A CNN analysis of federal health data last month found that during one week, the average rate of Covid-19 deaths was more than four times higher in the 10 least-vaccinated states compared to the 10 most-vaccinated states.
After the Biden administration announced last month that new vaccination rules would be imposed on federal workers and large employers, many private companies and public bodies began establishing compliance rules.
At Boeing, with many of its 140,000 employees working stateside, the aerospace giant announced that its US-based employees will need to show proof of vaccination or "have an approved reasonable accommodation" by December 8.
Smaller employers in certain cities are also working to stay in compliance. In the 30 days since New York City started enforcing its own vaccine requirement for most indoor activities, authorities have generally found success, Mayor Bill de Blasio said Wednesday.
Around 31,000 inspections have been conducted, which includes installation of proper signage and checking for proof of vaccination, the mayor said.
Around 6,000 warnings were issued, according to NYC Small Businesses Services commissioner Jonnel Doris, yet de Blasio said only 15 businesses following the warnings were still found to be in violation and fined.
"To all the small business owners, to all the employees who made this work: Thank you," de Blasio said.
The city's overall vaccination rate has increased by 9% since the city's mandate began, he said.
As for public employees in other cities, approximately 812 Boston city employees are still not in compliance with the city's Covid-19 regulations, down from 1,400 reported last week, according to a statement from Mayor Kim Janey's office. These employees have been placed on unpaid leave.
The Los Angeles Unified School District, the nation's second-largest, has pushed back its deadline for teachers and employees to be fully vaccinated against Covid-19 until Friday, according to a district spokesperson.
While health officials work to get as many first doses into the arms of Americans as possible, federal health data shows that the rate of boosters being administered is outpacing initial inoculations.
An average of 813,690 doses are being administered each day, but first doses -- or new vaccinations -- account for only about a quarter of all doses being administered, according to CDC data.
Booster doses of the Pfizer/BioNTech vaccine have been authorized for those at higher risk for Covid-19, and advisers at the US Food and Drug Administration are set to meet Thursday and Friday to review data and consider booster applications from Moderna as well as Johnson & Johnson.
An ongoing conversation among health experts is whether a mix-and-match strategy of using a booster from a different vaccine maker may prove safe or even more beneficial.
A preprint of a National Institutes of Health study, which has yet to be peer-reviewed or published, suggests that mixing boosters in different combinations among the three vaccines produced a robust immune response.
"The most important takeaways are two things. One is that all of these different nine combinations are safe, as in there are no new or different side effects, so all of these appear to be safe," CNN medical analyst and emergency physician Dr. Leana Wen told CNN on Wednesday.
"The second big takeaway is that all of these combinations induced a pretty strong, robust antibody response. So that actually justifies the mix-and-match approach," she said.
The Moderna application will be considered Thursday, and Johnson & Johnson's is set for Friday. Discussion from members of the FDA's Vaccines and Related Biological Products Advisory Committee, or VRBPAC, will then turn to mix-and-match boosters.