The rush is on to get children immunized before many schools open next week.
Nurses at Collin County Health Care say they've averaged about 200 people per day bringing children to get vaccinated for the past two weeks.
Bob Jameson said his son's school said students needed immunizations before picking up his schedule Tuesday. He and his son beat the afternoon crowd, which was standing-room only.
In previous years, lines have extended outside, with people waiting in triple-digit heat.
But Collin County is still expecting a last-minute push. With thousands of students still needing shots, clinics expect that lines will extend outside of the building, even with expanded clinic hours.
"I think we'll still have a last-minute rush, probably come Thursday, Friday [and] probably the first day of school also," said Christie Hix, Collin County director of immunizations.
This year, nothing has changed for students from elementary through high school. Seventh-grade students are having regular immunizations phased in.
Hix said the only real change is for college students, who must be immunized for meningitis.
"Last year, it was only required for those staying in the dorm to get a meningitis shot," she said. "This year, they're actually requiring it for all college-entry students."