Coronavirus is on the rise in the U.S., prompting questions about when Americans can roll up their sleeves for the next COVID-19 vaccine.

COVID-19 hospitalizations have been increasing for six straight weeks. While levels remain far below previous coronavirus waves in the U.S., it’s still the first increase since winter, and it has even prompted the return of mask mandates for a handful of businesses and schools.

The Biden administration estimates that 97% of Americans ages 16 and over have some level of COVID-19 immunity through vaccination, previous infection or both. The number may sound promising – so why do people need another round of shots? Because that protection can fade in a matter of months, leaving individuals vulnerable to COVID-19 once again.

“Immunity is stronger today than at any other point in the outbreak,” Mandy Cohen, the director of the Centers for Disease Control and Prevention, said in a recent video statement. “That means we're moving towards COVID-19 being a more manageable illness with less severe illness. Having antibodies is like a shield, but we still need to be cautious because that protection does decrease over time.”

Rollout of the shots is expected in mid-September, according to officials with the CDC and the Food and Drug Administration.

The shots from Moderna, Pfizer and Novavax first need authorization from the FDA. After that, the CDC’s committee of outside vaccine experts will gather to recommend who should be eligible for the shots. That meeting is scheduled for Sept. 12. Then, the CDC director must sign off on the recommendations before shots can be administered.

For undervaccinated or unvaccinated Americans – especially those who are at high risk for severe disease – Cohen says it might be best for them to roll up their sleeves now for the shots that are currently available.

“Those who have never been vaccinated and then some people who are older and at higher risk for a COVID infection might be best to get the existing COVID shot now and not wait,” Cohen said, noting that individuals should talk to their doctor first.

But Cohen added that “if you do get the current COVID-19 vaccine now or in early September, it could delay your ability to get this updated vaccine that's coming out in the middle of September.”

The updated shots target XBB.1.5, which was responsible for less than 5% of new coronavirus infections in recent weeks.

The variant scene has changed significantly since the Biden administration advised vaccine makers to target the XBB strain in June. Now, EG.5, or “eris,” is the dominant strain circulating, causing over 20% of new cases.

But all the strains circulating are still descendants of omicron, so experts believe the shots will still protect against severe COVID-19 from the variants.

A Biden administration official told reporters last week, “FDA expects that once available, the updated vaccines will similarly provide protection against the most serious outcomes of the disease that may result from currently circulating variants.”

Additionally, experts are keeping a close eye on how BA.2.86, a new strain that is highly mutated, could affect the shots.

“The CDC is closely tracking a new variant which does have a number of changes or mutations that do make it distinct and different from the older versions of the virus,” Cohen said. “So we're working as fast as we can to understand this new variant and what impact it might have on how severe the COVID disease will get or how well our vaccines work against it.”

Most Americans will receive the shot cost-free through their insurance. For uninsured Americans, the Biden administration is working on a program that will offer free shots at pharmacies. That program might not be available on the same day the shots are authorized but is expected to be up and running within a couple of weeks of the date.

Uninsured Americans will have immediate access to the shots for free at community health centers and individual providers as soon as they roll out.

Historically, vaccine uptake decreases each time a new coronavirus shot is offered.

Just 17% of Americans as of May rolled up their sleeves for the latest round of shots offered. That’s a steep drop from the first shot, which saw 81% of the population roll up their sleeves.

But there are reasons to be hopeful that uptake of the shots could be higher this time around. A survey from KFF found that more than half of adults said they are likely to get another COVID-19 booster shot if it’s offered annually like the flu shot.