WASHINGTON (NYTIMES) - The campaign to vaccinate young children in the United States against the coronavirus will not look like what it did for adults.

There will be no mass inoculation sites. Paediatricians will be enlisted to help work with parents. Even the vials - and the needles to administer doses - will be smaller.

Biden administration officials, anticipating that regulators will make the vaccines available to children aged five to 11 years in the coming weeks, laid out plans on Wednesday (Oct 20) to ensure that about 25,000 paediatric or primary care offices, thousands of pharmacies, and hundreds of school and rural health clinics will be ready to administer shots if the vaccine receives federal authorisation.

The campaign aims to fulfil the unique needs of 28 million people in the US, largely still in elementary school, while absorbing the lessons from the roll-out of vaccines to other age groups. The five-to-11 range has far more members than the teenage cohort already approved to receive the vaccine.

"Kids have different needs than adults, and our operational planning is geared to meet those specific needs, including by offering vaccinations in settings that parents and kids are familiar with and trust," Mr Biden's coronavirus response coordinator Jeffrey Zients told reporters.

"So we are going to be ready, pending the FDA and CDC decision that will be based on science," he said, referring to the US Food and Drug Administration and the Centres for Disease Control and Prevention.

The White House announcement came as regulators greatly expanded the number of Americans eligible for booster shots. The FDA authorised boosters on Wednesday for tens of millions of recipients of Moderna's two-dose coronavirus vaccine and the roughly 15 million who got Johnson & Johnson's single-dose shot.

The agency also updated its authorisations for all three types - Moderna, Johnson & Johnson, and Pfizer-BioNTech - to allow medical providers to give people a different vaccine as a booster shot, a strategy known as "mix and match".

Still, with the school year well under way and the holiday travel season approaching, much of the country has been waiting to see when younger children can receive their first dose.

This month, Pfizer and BioNTech asked the FDA to authorise emergency use of their vaccine for children aged five to 11 years. A meeting to discuss the authorisation is set for next Tuesday, and an FDA ruling could come in the days after, possibly clearing a path for the CDC to make recommendations on a paediatric dose in early November.

Regulators have delayed a decision to authorise Moderna's vaccine for adolescents over concerns about rare cases of heart problems. Both Pfizer-BioNTech and Moderna have expanded the scope of their trials for children aged five to 11 years as a precautionary measure to detect any rare side effects.

In laying out a plan for distribution before regulators have granted their approval, the White House is exposing itself to criticism that it is acting before the scientists.

Administration officials say they want to make sure that any barriers to access are removed if children are approved to receive the vaccine. Ms Sonya Bernstein, a senior policy adviser for the White House Covid-19 Response Team, stressed that the approval process was independent of the administration's plans.

"We know that access is going to be critical here," Ms Bernstein said, adding that the administration had in recent weeks explored ways to provide a "kid-friendly experience that makes sure that we're getting shots in arms with trusted providers in ways that makes parents feel comfortable".

Other experts said it made sense for officials to plan ahead.

"The reality is that they would be absolutely foolish not to have a well-detailed plan prepared," said Dr Howard Forman, a professor of public health policy at Yale University, adding that health officials in "clinical practices and schools and other settings where children interact should be thinking about this right now".

The five-to-11 age group is far larger than the 17 million children aged 12 to 15 years, who became eligible for the Pfizer-BioNTech vaccine in May. To ensure enough supply, the administration has purchased sufficient doses to vaccinate the younger age group, and officials say they intend to ship 15 million doses to the states immediately.

Taking cues from what worked when shots were opened to teenagers, whose vaccinations generally require parental consent, officials are also leaning heavily on local health experts, who they believe are more trusted in their communities and can help reach high-risk children.

"Children's hospitals and health systems will be a critical part of our efforts to advance equity and ensure access for our nation's highest-risk kids, including those with obesity, diabetes, asthma or immunosuppression," the guidance read.

If the approval for the Pfizer-BioNTech vaccine goes through, the Federal Emergency Management Agency will provide reimbursement for "full funding to states to support vaccinations and outreach", Ms Bernstein said.

While the administration aims to eliminate the types of availability and efficiency problems that plagued the initial vaccine process, reluctance among parents remains an issue.

In June, the CDC published data showing that Pfizer-BioNTech and Moderna vaccines may have caused myocarditis and pericarditis in more than 1,200 Americans, including about 500 younger than 30.

Myocarditis is the inflammation of the heart muscle, while pericarditis is the inflammation of the membrane surrounding the heart. The symptoms typically appeared within two weeks and were more common in young men and boys.

According to polling by the Kaiser Family Foundation published in late September, only about one in three parents of children aged five to 11 years planned to get their children inoculated "right away" once a vaccine is authorised. Another third said they wanted to "wait and see" how the vaccine affected children.

But that same polling showed that reluctance among parents of teenagers had dropped in the months since vaccines had become available, and nearly half of parents of those aged 12 to 17 said their teenagers had received at least one dose.

Mr Zients, treading carefully on a politically sensitive topic, indicated on Wednesday that the administration would support state coronavirus vaccine mandates for children.

"We know that, in general, requirements work, and we support states and school districts taking actions to ensure that everyone who is eligible get vaccinated, but again, those decisions should be made at the state and local level," he said.

Hospitalisations and deaths from Covid-19 are uncommon in children, according to data collected by the American Academy of Paediatrics, but experts point out that children are still susceptible to serious or long-haul versions of the illness.

"Of course, adults are going to have much more severe diseases, but that doesn't mean that children are not affected as well," said Dr Flor Munoz-Rivas, an associate professor of paediatric infectious diseases at Baylor College of Medicine.

"Children are typically ones that are vectors of transmitting the virus," she said, and preventing them from getting infected "could potentially also have some effect" in slowing the spread of the virus.

Other experts applauded the administration's planning to ensure that vaccines would be available for children if the FDA and CDC authorise them.

"Laying this advance groundwork, ensuring supply is available at physician practices and that a patient's own physician is available to answer questions, is critical to the continued success of this roll-out," Dr Gerald Harmon, the president of the American Medical Association, said in a statement.