In the first week of availability, around 900,000 children received their first doses, or around 3% of those eligible. Another 700,000 have appointments scheduled at major pharmacies like CVS and Walgreens, plus an unknown number who have appointments with pediatricians or at hospitals. 

In general, younger kids, who receive a one-third dose of the adult shot, can expect fewer side effects. Pfizer’s clinical trial showed that the most common was pain at the injection site, similar to vaccine recipients in other age groups. After receiving the second dose, 39% of young children experienced fatigue, and 28% reported headaches, compared with 65% and 61% of trial participants ages 16 to 25. Fewer than 10% of children experienced fever and muscle pain. The study showed no serious side effects, including myocarditis, an inflammation of the heart muscle that occurred extremely rarely in adults after receiving an mRNA vaccine. Other side effects like diarrhea, joint pain, and vomiting were reported in less than 10% of young children. According to the CDC, side effects should go away a few days after receiving the vaccine.

Research by the Kaiser Family Foundation found that 27% of parents are eager to get a vaccine for their younger children. Meanwhile, 30% said they will definitely not get the vaccine for their child. Around two-thirds of the 1,519 adults surveyed expressed concerns that the vaccine may affect their child’s future fertility. The American Academy of Pediatrics has said that there is no evidence that the COVID-19 vaccine leads to a loss of fertility or affects puberty.

“Of course, we always need to keep our eyes open [for side effects],” Paul Offit, director of the Vaccine Education Center, a program led by the World Health Organization to provide accurate and up-to-date information about vaccines, told Fortune in an email. “But systems are in place to detect even very rare adverse events.”

First lady Jill Biden plans to travel around the country in the coming weeks to visit schools and urge parents to get their children vaccinated, NPR reports. So far, the CDC has authorized only the Pfizer-BioNTech vaccine for emergency use in children. Moderna expects to seek emergency authorization late this year or early next after expanding its trial size, while Johnson & Johnson’s clinical trial for kids is still underway.