The United States is bracing for another unpredictable respiratory virus season this fall and winter. But this time, we'll have a host of new vaccines that can help individuals and the nation withstand waves of infection.

Last year showed how the coronavirus is not the only major threat to the health-care system as a surge in respiratory syncytial virus (RSV) overwhelmed children's hospitals and pediatric offices, and back-to-back waves of COVID, influenza and RSV in seniors strained other hospitals.

In the coming weeks and months, health officials will roll out brand new immunizations for RSV and updated COVID boosters — alongside the usual flu shot campaign.

Here's what you should know.

What's happening with the new COVID booster?

New COVID booster shots with an updated formula targeting XBB subvariants of the virus is expected to hit the market in late September, pending regulatory approvals by the Food and Drug Administration, guidance from the Centers for Disease Control and Prevention on who should get an updated shot, and timely delivery by manufacturers.

Federal health officials are shifting to an annual model for COVID boosters for all age groups, similar to flu shots. Proponents say this eases confusion surrounding coronavirus vaccination, although critics argue that COVID can also surge in spring and summer, leaving people susceptible to worse outcomes because of waning immunity.

This is also the first time the federal government is not buying all the COVID shots, meaning doctors, hospitals and pharmacies must order them directly. They'll still be free for most people because most insurance plans will cover them. The Biden administration is launching a program to keep coronavirus vaccines free for people without health insurance, but they probably won't be available at pharmacies until mid-October at the earliest.

Most consumers with health insurance should be able to find the updated coronavirus vaccines at national pharmacy chains within a week or so after the FDA and CDC actions.

Will the new COVID booster work against the new variants?

Since the highly transmissible omicron variant sparked an explosion of cases in winter 2021-2022, its descendants have caused the vast majority of new infections in the United States because they are adept at bypassing immunity from previous vaccines and infections. The new booster formula is designed to target the XBB lineage of the omicron variant that has been most common in 2023.

But a closely related subvariant EG.5 is on the rise and recently became the most common omicron descendant circulating in the United States, although most are still different versions of XBB.

Experts say the updated boosters should still be effective against EG.5 because of its similarities to XBB, while there's less overlap with the BA.5 subvariant the existing booster targets. Still, it offers a reminder of the challenges of trying to quash a virus that can evolve faster than our attempts to adapt our defenses to it.

Health authorities are also watching BA.2.86, another omicron descendant. Only several cases had been confirmed worldwide as of Aug. 18, including one in Michigan, but the subvariant caught the interest of scientists because it is highly mutated, with evidence to suggest it is better at evading immunity than the XBB line. A federal health official monitoring the new subvariant says the new booster should work against it, but testing is still underway.

When should I get my COVID booster?

This is one of the most common questions we get and the answer is usually the same: Talk to your doctor. There's no easy formula for when someone should get boosted against an ever-evolving virus spreading in a society where everyone has different levels of immunity. That said, here are factors to consider and discuss with your medical professionals.

What's your risk factor? The people most in need of regular boosters are older adults and those who are severely immunocompromised, such as organ transplant recipients and people undergoing chemotherapy. They qualified for a second dose of the bivalent booster that hit the market last September.

With cases rising again, your doctor might suggest getting that shot as soon as possible if you are in a high-risk group, haven't had a shot or infection in recent months, and plan to travel. But new research, which has not been peer reviewed, suggests a second bivalent shot has not made a significant difference in antibody response to the virus. Some doctors might instead advise you to take elevated precautions, such as wearing an N95 mask or avoiding crowds until the new booster is available. The CDC hasn't taken a stance on whether you should get a second bivalent booster or wait.

When do you want peak protection? While vaccines have conferred a durable shield against severe illness for most people, it's not as effective for those without boosters. The booster's protection against infection is much weaker than protection against hospitalization, and it fades within weeks or several months. If you're a healthy young adult trying to avoid getting sick before the holidays, you should consider whether you want to be first in line for a new booster in September or wait until November, closer to holiday travel and family gatherings.

What are the new RSV vaccines?

RSV is one of the most common respiratory viruses out there and poses a heightened risk to seniors and infants. Now both groups can be protected against the virus.

Regulators have approved two vaccines to prevent RSV in adults 60 and older: Pfizer's Abrysvo and GSK's Arexvy. The CDC isn't recommending everyone in that group to get vaccinated, but instead to talk to your doctor about the benefits and risks. Seniors with underlying health problems like heart or lung disease or declining immune systems are at higher risk for severe RSV disease. The clinical trials also detected rare severe side effects which manufacturers have been directed to closely monitor as the vaccine is widely administered. That might be a reason for otherwise healthy seniors to hold off on RSV vaccination this year. We've also prepared a more detailed FAQ on the GSK RSV vaccine for older adults.

The CDC also recently recommended a new preventive monoclonal antibody treatment called Beyfortus to protect all infants under the age of 8 months and high-risk toddlers up to age 19 months from RSV. It's not a vaccine but essentially works like one by protecting babies for at least five months, enough for one respiratory virus season. The vast majority of young children are exposed to RSV and develop mild cold-like symptoms, but infants are more likely to be hospitalized because of their smaller airways. There's already another RSV preventive treatment for high-risk toddlers, but this is the first universal protection for infants.

Another looming option is a maternal vaccine administered in the third trimester that would protect infants from severe illness for six months after birth. That vaccine is further behind in regulatory approval and may not be approved until later in the fall.

When should I get the new RSV vaccine?

For older adults, the CDC suggests doctors offer RSV vaccines to patients they believe would benefit as soon as they become available.

For infants born shortly before or during RSV season, the CDC recommends receiving Beyfortus within 1 week of birth or close to discharge from the hospital. The ideal timing is shortly before the season starts but it can be administered at any time during the season.

The RSV season typically starts in the fall and peaks in the winter, depending on the region of the country, although the past two seasons started earlier than usual. Patients can seek guidance from their doctors on the timing of the RSV season in their community.

RSV vaccination is still recommended for young children regardless of prior infection. The CDC plans to issue guidance on which toddlers are considered at risk of severe RSV disease by the end of September.

How do I get new RSV vaccines?

Pfizer and GSK say their vaccines have already started becoming available at major pharmacy retailers. Walgreens said appointments are available in most states, but its pharmacy employees are not yet authorized to administer the RSV vaccine in the District, Maryland and Virginia. In a handful of states, consumers may need a doctor's prescription. Doctors' offices say they are ordering the vaccine this month and should be available for patients by September.

The RSV vaccines for older adults should be covered by Medicare Part D, but free coverage under private insurers may be inconsistent.

Getting the monoclonal antibodies for infants, however, might be trickier. There's a host of complications because Beyfortus is technically not a vaccine even though it acts as one. That means medical professionals qualified to administer vaccines may not be qualified to administer the antibody treatment, and the systems for tracking and distributing vaccines cannot be easily updated for this new immunization.

It's also expensive — $495 per dose. While insurers are required to cover recommended immunizations, they don't have to do so immediately. So doctors' offices will have to decide whether to buy the treatments with uncertainty about whether they'll get reimbursed and how many parents actually want a new treatment for their children. Sanofi, which markets the treatment, says it is addressing these concerns by allowing providers to wait until the end of the RSV season to pay the company back.

The vaccine should also be free for uninsured or underinsured children through the federal Vaccines for Children program, but it's unclear whether that will be ready in time for this RSV season. The CDC says it's working to immunize as many eligible children as they can through that program. Parents may need to call around to find a place offering the immunization.

What's the latest with flu vaccine?

There's nothing special about flu shots this year. The CDC has already adopted its annual recommendations for everyone 6 months and older to get vaccinated, with some exceptions. There's an updated formula, as is usually the case.

Should I get my COVID, flu and RSV vaccines together?

This is a conundrum for health officials who are weighing maximum protection against maximum convenience in considering how to administer these three shots for seniors.

They are confident influenza and coronavirus vaccines can be safely given at the same time across all ages, although there may be reasons to space them apart, such as if someone had a recent COVID infection or if someone wants a flu shot closer to flu season and a COVID booster closer to the holidays.

But there's more hesitation to administer an RSV vaccine at the same time as the flu shot. In clinical trials, there were rare instances of patients who received the RSV vaccine at the same time as an influenza shot suffering severe side effects, but experts say it's not clear whether this is a statistical fluke or a consequence of administering the vaccines together. Because side effects were rare, some doctors may advise giving those shots at the same time anyway if a patient has mobility issues or other difficulties returning to their doctor's office or pharmacy.

The CDC says it is acceptable to give the RSV vaccine at the same time as other vaccines. But there is no data on how the RSV vaccine will interact with the updated COVID booster.

For young children getting the new RSV therapeutic, Beyfortus, the CDC recommends that it be given at the same time as other "age-appropriate" vaccines.

The Washington Post's Laurie McGinley contributed to this report.