LOUISVILLE, Ky. (WDRB) -- Medical providers in Louisville are preparing to offer COVID-19 vaccines to infants, toddlers and preschoolers. 

The U.S. opened vaccines to children over the weekend, and the first shots will become available this week, expanding the nation’s vaccination campaign to children as young as six months.

The state of Kentucky told Norton Healthcare that the shipment of COVID vaccines for kids was slightly delayed and should arrive mid-week.

Norton said it's still on schedule to start offering the vaccine this week.

"It's a big day. Now, all kids six months and older can be protected against COVID-19. This has many parents really incredibly relieved," said Dr. Kristina Bryant, Norton Children's Infectious Disease.

Hospitals like Norton can't just immediately start vaccinating. The shots for children are the same vaccine, but it's a smaller dose. Norton expects its first shipment to have about half of the 20,000 doses it ordered.

Norton plans to start scheduling and then vaccinating likely starting Friday. A pop-up location at Audubon Hospital may be planned for a few weekends, depending on demand.

"We're going to monitor the utilization of that vaccine clinic. We expect like we've seen with our other vaccines as they come out, we see a big rush at the beginning for those that are anticipating, sitting there watching, waiting for their opportunity to schedule, said Carrie Regnier, Norton Healthcare COVID-19 Director.

In a statement, UofL Healthcare told WDRB that it has no plans in place right now to offer the vaccine for children under five.

"Right now, UofL Health doesn’t have plans to offer the vaccine to those under 5 – at least not an immediate release plan. We suggest parents call their pediatricians."

The shots offer young children protection from hospitalization, death and possible long-term complications that are still not clearly understood, the CDC's advisory panel said.

The government has already been gearing up for the vaccine expansion, with millions of doses ordered for distribution to doctors, hospitals and community health clinics around the country.

Roughly 18 million kids will be eligible, but it remains to be seen how many will ultimately get the vaccines. Less than a third of children ages 5 to 11 have done so since vaccination opened up to them last November.

Here are some things to know:

WHAT KINDS ARE AVAILABLE?

Two brands — Pfizer and Moderna — got the green light Friday from the FDA and Saturday from the CDC. The vaccines use the same technology but are being offered at different dose sizes and number of shots for the youngest kids.

Pfizer’s vaccine is for children 6 months to 4 years old. The dose is one-tenth of the adult dose, and three shots are needed. The first two are given three weeks apart, and the last at least two months later.

Moderna’s is two shots, each a quarter of its adult dose, given about four weeks apart for kids 6 months through 5 years old. The FDA also approved a third dose, at least a month after the second shot, for children with immune conditions that make them more vulnerable to serious illness.

HOW WELL DO THEY WORK?

In studies, vaccinated youngsters developed levels of virus-fighting antibodies as strong as young adults, suggesting that the kid-size doses protect against coronavirus infections.

However, exactly how well they work is hard to pin down, especially when it comes to the Pfizer vaccine.

Two doses of Moderna appeared to be only about 40% effective at preventing milder infections at a time when the omicron variant was causing most COVID-19 illnesses. Pfizer presented study information suggesting the company saw 80% with its three shots. But the Pfizer data was so limited — and based on such a small number of cases — that experts and federal officials say they don’t feel there is a reliable estimate yet.

WHICH VACCINE SHOULD MY CHILD GET?

Either one, said Dr. Peter Marks, the FDA's vaccine chief.

“Whatever vaccine your health care provider, pediatrician has, that’s what I would give my child,’’ Marks said Friday.

The doses haven't been tested against each other, so experts say there’s no way to tell if one is better.

One consideration: It takes roughly three months to complete the Pfizer three-shot series, but just one month for Moderna's two shots. So families eager to get children protected quickly might want Moderna.

CAN CHILDREN GET OTHER VACCINES AT THE SAME TIME?

It’s common for little kids to get more than one vaccine during a doctor’s visit.

In studies of the Moderna and Pfizer shots in infants and toddlers, other vaccinations were not given at the same time so there is no data on potential side effects when that happens.

But problems have not been identified in older children or adults when COVID-19 shots and other vaccinations were given together, and the CDC is advising that it's safe for younger children as well.

WHAT IF MY CHILD RECENTLY HAD COVID-19?

About three-quarters of children of all ages are estimated to have been infected at some point. For older ages, the CDC has recommended vaccination anyway to lower the chances of reinfection.

Experts have noted re-infections among previously infected people and say the highest levels of protection occur in those who were both vaccinated and previously infected.

The CDC has said people may consider waiting about three months after an infection to be vaccinated.

Copyright 2022. WDRB Media. The Associated Press contributed to this report. All rights reserved.