Lucien Wiggins, 12, arrived at Tufts Children’s Hospital by ambulance June 7 with chest pains, dizziness and high levels of a protein in his blood that indicated inflammation of his heart. The symptoms had begun a day earlier, the morning after his second vaccination with the Pfizer-BioNTech mRNA shot.

For Dr. Sara Ross, chief of pediatric critical care at the Boston hospital, the event confirmed a doubt she’d been nursing: Was the country pushing its luck by vaccinating children against COVID at a time when the disease was relatively mild in the young — and skepticism of vaccines was frighteningly high?

“I have practiced pediatric ICU for almost 15 years and I have never taken care of a single patient with a vaccine-related complication until now,” Ross told Kaiser Health News. “Our standard for safety seems to be different for all the other vaccines we expose children to.”