The percentage of Alaska children who are up to date on their routine vaccinations has fallen considerably since the beginning of the pandemic, prompting concern among health experts about the return of certain serious illnesses that had been all but eradicated in the U.S. until recently.

Although there have been no outbreaks of vaccine-preventable illnesses — including measles, mumps or polio — identified in Alaska so far, recent flare-ups of those diseases in the Lower 48 and multiple countries are part of a disturbing trend that epidemiologists have linked to lower vaccine coverage d...