Now that  federal health officials have cleared the way for COVID-19 vaccines for children as young as 6 months old, doctors around the country are now administering the first shots to infants, toddlers and preschoolers.

Many more providers are preparing to receive their first deliveries of kids’ vaccines from Moderna as well as Pfizer and its partner BioNTech over the coming weeks.

Here’s what parents need to know about the new, lower-dose vaccines for young children now being rolled out: 

Where can I find the shots for my child? 

In planning the rollout, the Biden administration says they expect that most children between 6 months and 5 years old will get shots through their regular pediatricians or family doctors. COVID-19 immunizations can be administered alongside the other routine vaccines doctors already give to kids. 

“We encourage parents to reach out to their pediatricians or family doctors directly to learn more about their plans to offer appointments,” an official told reporters earlier this month.

However, not every pediatrician’s office has sought out the shots. Officials also acknowledge not every child in this age group will have a doctor to turn to. 

Parents shopping around for a specific brand may also be out of luck with their regular physician, given that doctors will likely only carry one of the two vaccines.

For these parents, a growing number of sites are being added to the Biden administration’s vaccines.gov website, which allows users to search for providers in their local area, and to filter for either Pfizer or Moderna’s shots. 

Around half of doctors who do childhood vaccinations are planning to offer shots even to kids who are not their regular patients, a CDC survey found. Many local health departments and community health centers are also planning to offer shots for young children.

In Minnesota, health officials announced that Pfizer’s shots will be available for these ages at the state’s Mall of America vaccination clinic. In New York City, authorities will offer Moderna’s shots for young kids at “hubs” located around the city.

Around a fifth of the 10 million shots made available for the initial waves of kids’ vaccinations were allocated to pharmacies. Walgreens, CVS, and Walmart are among the national chain drug stores that say they are now accepting appointments for younger children. 

Pharmacists are only authorized to give the shots to children ages 3 and up. However, at their 1,100 MinuteClinic locations, CVS says clinicians will be able to administer Pfizer shots to children as young as 18 months old.

What’s the difference between Pfizer and Moderna?

Moderna and Pfizer-BioNTech’s doses come in different sizes and different schedules for young children, as recommended by the CDC. 

To be fully vaccinated with Moderna’s vaccine, kids between 6 months old and 5 years old will need to get two shots spaced four to eight weeks apart. Moderna’s doses are 25 micrograms, a fraction of the 100-microgram primary series rolled out last year for adults. 

To be fully vaccinated with Pfizer’s vaccine, children 6 months old to 4 years old will need a total of three shots. Those are spaced three to eight weeks between the first two doses, and another eight weeks until the third. Pfizer’s shots are sized at 3 micrograms, just one-tenth of the 30-microgram shots for those 12 and older.

That timing alone might be enough for some parents deciding between brands to immunize their children before returning to school in the fall.

“If you want to put your child back in day care or lower school in September, you have to take the Moderna vaccine. You cannot do it on Pfizer’s schedule. And we know that two doses does not protect, from Pfizer,” Moderna’s CEO Stéphane Bancel said last week at the Jefferies Healthcare Conference.

However, Pfizer has sought to underscore that two doses of its vaccine did appear to offer some protection against the virus, even if it fell short of the FDA’s original benchmarks. Both companies are also planning to study additional doses in young children, which may be adapted for the Omicron variant.

“Two doses could offer some potential benefit. But the goal here is to get to a high level of efficacy, and get children vaccinated as quickly as we could,” Pfizer’s William Gruber told the CDC’s outside advisers on Friday. 

At a briefing with reporters on Friday, the FDA’s top vaccines official Dr. Peter Marks acknowledged the “nuanced benefits and risks compared to each other” but urged parents to seek out the first shots available to them.

“It may be that the Moderna vaccine brings an immune response slightly more rapidly. On the other hand, the three dose Pfizer regimen may also bring a greater immune response after the third dose. And there are some subtle differences in the safety profile,” Marks said.

Why are COVID vaccines recommended for such young kids?

Panels of both the FDA and CDC’s outside vaccine advisers voted unanimously last week to back making shots available for children as young as 6 months old. 

Younger children are generally at lower risk of severe COVID-19 compared to their older peers and adults, and many asymptomatic cases have likely gone unreported. However, CDC officials told the committees that the disease has continued to inflict a significant toll on young children. 

Many children have been hospitalized and more than 200 kids in this age group have died — including some with no underlying medical conditions. The disease’s impact far outpaces other diseases that Americans now regularly vaccinate their children against.

“There is a lot of information circulating that, well, ‘I had the Omicron variant, or my child had the Omicron variant, and vaccination is not important,'” Marks said Friday. 

Data presented to the CDC’s advisers suggest that nearly three-quarters of children ages 6 months to 4 years old have antibodies from surviving a previous infection. But they could still be vulnerable to catching it again. 

“There are emerging data to suggest that the Omicron variant does not produce the kind of excellent immune response against a wide range of COVID-19 variants that the vaccinations do,” he added.

Will young children need boosters? Will they be able to get updated boosters for new variants?

The shots come as the FDA is preparing to weigh revisions to COVID-19 vaccines adapted for the Omicron variant later this month, ahead of an expected fall booster season for all ages.

“If it turns out that there is a very major change in strains that needs to occur in the fall, we will adjust for that and make sure that there is an option available for the youngest children and throughout the pediatric age range as appropriate,” Marks said.

Moderna is already planning to begin testing its boosters adapted for the Omicron variant in children under 6 starting this week, with the booster given at least three months after their second dose. 

“We hope by early fall we’ll be able to bring forward the booster immunogenicity and safety data for this age group,” Moderna’s Dr. Rituparna Das told the CDC’s committee on Friday.

Pfizer and BioNTech are still in talks with the FDA about their plans to test updated versions of their shots in children, potentially targeted towards the BA.4 and BA.5 Omicron subvariants that now make up more than a third of new infections.

“I think it does need to be informed by the decisions that are made this month so we don’t go off on a tangent for something that, you know, frankly doesn’t become the vaccine in the future,” Pfizer’s William Gruber told the CDC’s panel.

For now, Marks said there was no reason for parents to hold out for the updated shots.

“I would strongly recommend that, with the availability of this primary series, which provides excellent foundational immunity against a broad range of COVID-19 variants, that I would have children start this right now,” Marks said.