Historically, pediatric vaccines have focused on killer childhood diseases, but the pandemic has thrown a curve into that thinking. While the virus has been a deadly force among older adults, it's been shown to be mild in the young with deaths relatively minimal.

That's sparked an emerging debate among scientists about how critical it is that children be immunized. Some say the case for inoculating kids is less pressing, given that their outcomes tend to be so much better. Worldwide, the rollout of vaccines has prioritized older people and others at risk because of their health or occupation.

"Vaccines for polio, diphtheria and meningitis were all geared to eliminate the most dangerous diseases in children," said Michael Hefferon, an assistant professor in the pediatrics department at Queen's University in Ontario. "We now have almost the opposite. It's a disease of adults, and the older you get the more sinister it is. Therefore children are less relevant."