The toddler looking up at Dr. Melanie Seifman in her Washington, D.C., exam room seems a little dazed.

It could be because she just woke up from a nap at daycare. It could be that she remembers the shots she got last time, and she knows what’s coming.

The little girl is catching up on some vaccines she’s behind on: missing doses of the DTaP and polio vaccines. She’s over two years old — both of those shots are supposed to happen at a baby’s six-month check up.

“It happens a lot,” Siefman says. The Unity Health Care clinic, where Siefman practices, serves mostly low-income, mostly African-American patients. She says her patients often miss vaccinations because of struggles in their parents’ lives. The reasons include: “transportation, couldn’t get off work, didn’t have insurance and didn’t know that they could come in without insurance.”

During this recent measles outbreak, there’s been a lot of discussion about the religious and ideological reasons behind low vaccination rates, especially in places like Washington state and New York.

Read more at NPR