Your Questions About Covid Vaccine Dosage for Children, Answered

We turned to five experts to answer these frequently-asked questions.,


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Children ages 5 to 11 may be eligible for the Pfizer-BioNTech Covid vaccine by early next month: two shots spaced three weeks apart. But unlike kids 12 and older, who get the same dosage as adults, the kids in the younger age group will receive 10 micrograms of vaccine per dose, or one-third the amount that a 12-year-old would get.

This has created some confusion for parents of 11-year-olds on the cusp of turning 12. Is it best to hold out for the larger dose? Or is it better to get the smaller dose right away? Does the weight or height of the child make any difference?

Five experts in immunology and infectious diseases agreed: The appropriate dosage is best determined by a child’s age — not their size. So if your 11-year-old is able to get the shot starting in November, do it right away rather than waiting for your child to turn 12.

The virus isn’t going away anytime soon, they said. And different variants could potentially make the virus more infectious or dangerous, said Donna L. Farber, a professor of microbiology and immunology at the Columbia University College of Physicians and Surgeons.

The sooner your child can be vaccinated the better, the experts said. The shot greatly reduces the chance of becoming severely ill from Covid and curbs the likelihood of getting infected in the first place and then passing that infection to others.

“Just do it,” Dr. Farber said.

Although many children who contract the virus will recover easily, “we cannot predict who is going to be very sick,” said Dr. Octavio Ramilo, chief of infectious diseases at Nationwide Children’s Hospital and a professor of pediatrics at Ohio State University.

More than 1,000 kids were hospitalized from Covid at Nationwide over the last year and a half, he added, and approximately half of them had been previously healthy.

Dr. Monica Gandhi, a professor of medicine and an infectious diseases expert at the University of California, San Francisco, said her younger son, who is turning 12 in February, will get vaccinated as soon as possible.

“Since the 10 microgram dose is so effective, I would stick with that dose for an 11-year-old,” she advised.

The two-dose 10 microgram shot in the vaccine trial of 5- to 11-year-olds had a nearly 91 percent efficacy rate, indicating it is very effective at preventing symptomatic infection in young children. In addition, there were not any new or unexpected side effects or safety concerns, according to a Food and Drug Administration review of Pfizer’s vaccine data.

It doesn’t matter whether your child is smaller or larger than other kids their age when it comes to vaccines, the experts said.

Weight is an important factor when you give a young child medication like Tylenol because there is a wide variation in weight from infancy throughout childhood and too much of the drug could be toxic.

The optimal vaccine dose, however, is dependent on age and tailored to minimize potential side effects. A small 5-year-old and a large 5-year-old will have immune systems that are “functionally similar,” said Dr. David J. Rawlings, chief of the division of immunology at Seattle Children’s Hospital and director of the Center for Immunity Immunotherapies at Seattle Children’s Research Institute.

And children in the 5 to 11 age group “have a really robust immune system,” he added. That means they can get a lower vaccine dose than those in the 12 to 17 age group and still produce the same number of antibodies.

What to Know About Covid-19 Booster Shots

The F.D.A. has authorized booster shots for millions of recipients of the Pfizer-BioNTech, Moderna and Johnson & Johnson vaccines. Pfizer and Moderna recipients who are eligible for a booster include people 65 and older, and younger adults at high risk of severe Covid-19 because of medical conditions or where they work. Eligible Pfizer and Moderna recipients can get a booster at least six months after their second dose. All Johnson & Johnson recipients will be eligible for a second shot at least two months after the first.

Yes. The F.D.A. has updated its authorizations to allow medical providers to boost people with a different vaccine than the one they initially received, a strategy known as “mix and match.” Whether you received Moderna, Johnson & Johnson or Pfizer-BioNTech, you may receive a booster of any other vaccine. Regulators have not recommended any one vaccine over another as a booster. They have also remained silent on whether it is preferable to stick with the same vaccine when possible.

The C.D.C. has said the conditions that qualify a person for a booster shot include: hypertension and heart disease; diabetes or obesity; cancer or blood disorders; weakened immune system; chronic lung, kidney or liver disease; dementia and certain disabilities. Pregnant women and current and former smokers are also eligible.

The F.D.A. authorized boosters for workers whose jobs put them at high risk of exposure to potentially infectious people. The C.D.C. says that group includes: emergency medical workers; education workers; food and agriculture workers; manufacturing workers; corrections workers; U.S. Postal Service workers; public transit workers; grocery store workers.

Yes. The C.D.C. says the Covid vaccine may be administered without regard to the timing of other vaccines, and many pharmacy sites are allowing people to schedule a flu shot at the same time as a booster dose.

As an added bonus, with the 10-microgram dose researchers saw less fever and chills after the second dose among the 5- to 11-year-olds than they saw in the older kids who received higher doses.

At higher doses, the researchers observed more side effects in the younger children.

The bottom line: The appropriate vaccine dose is not determined by weight and “there are no patient weight requirements for Covid-19 vaccination,” the Centers for Disease Control says.

Once a child enters puberty, “there are changes in the immune response,” Dr. Rawlings said, and their immune system becomes more like that of an adult. The cutoff of 12 was somewhat arbitrary, he added, but in general, as kids get older they have an immune system that becomes less efficient than that of younger children, hence the need for a bigger dose.

“From our studies in immune development, your immunological adulthood is much earlier than 18,” Dr. Farber said.

Another important consideration: Vaccine doses are spaced three weeks apart and it takes two weeks for the protection to fully set in after getting the second dose. So if you planned to wait, say, two months for your child to turn 12, you would need to factor in an additional five weeks before your child was fully protected.

It’s a gamble that is not worth taking, said Dr. Matthew P. Kronman, the associate medical director of infection prevention at Seattle Children’s Hospital.

“That would be like saying: OK, we’re going to drive to Grandma’s house and I’m going to wait 50 miles before putting my seatbelt on and I’ll just wear it for the last 50 miles. It doesn’t make a lot of logical sense,” Dr. Kronman said. “It’s better to get the protection now that we know will work, based on the age.”

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