As children got vaccinated against the coronavirus on Friday at the Children’s Hospital of Philadelphia pediatric care center in West Philadelphia, they joined more than 13,300 elementary-school-age kids who have already done so in Philadelphia.

Their shots were already exciting — finally being able to get protected against COVID-19 was a big deal for the little ones, and their parents — but Friday’s clinic included a special guest: first lady Jill Biden.

“Parents, we do absolutely everything to protect our kids. And in this pandemic, our parents did a great job,” said Biden, a Willow Grove native who opened her remarks joking about her Philadelphia accent and reminiscing about visiting the city during the holiday season as a child. “Now I am so excited that parents have another way to keep your families safe: a vaccine for children 5 and up.”

She arrived in Philadelphia the day after President Joe Biden announced his winter COVID-19 plan, which includes opening more vaccination clinics aimed at families and creating Medicaid-funded vaccine counseling visits for parents.

As she joined several families in CHOP’s post-vaccination room, Biden shook hands and congratulated them on getting vaccinated.

“It was easy, right? And now it’s going to protect you,” Biden told 7-year-old twins Iyanuolwa and Ifoeluwa Adesina, squatting down to talk to the girls and their mother.

Another mother, Sharena Smith, proudly showed her own vaccination card to Biden, saying, “We are all vaccinated.” Bella Sophia Pritchett, 7, who had just received a shot, screamed “Oh my God!” when Biden walked in. She ran up waving, paused, and then flew into the first lady’s arms.

Four million children 5 to 11 have been vaccinated since their age group became eligible on Nov. 2, according to the White House, along with 15 million adolescents.

But after an initial rush of highly interested families, the demand for kids’ shots has slowed, and both federal and state officials are hoping to accelerate vaccinations. Generally, that means persuading parents, who can be hesitant about vaccinating their children even if they themselves are vaccinated.

In Pennsylvania, more than 99,000 5-to-9-year-olds have gotten their first dose, nearly 17% of that population. More than a quarter of those living in Montgomery and Chester Counties, which have the state’s highest rates, have done so. For 10-to-14-year-olds, a third have at least one dose, nearly 240,000 children. In Philadelphia, 11.5% of children 5 to 11, or more than 13,000, had had at least one shot as of Thursday.

And in New Jersey, 12% of kids 5 to 11 have gotten vaccinated, state health commissioner Judith Persichilli said Monday.