The Knox County Health Department says 2010 vaccination guidelines have been adding up to weeks of middle school absenteeism across the county.
Sixth graders now need a proof of immunization certificate for chicken pox - tetanus - diphtheria and pertussis before they can start seventh grade.
But Mary Ann Harrison, nurse manager of the Immunization Program at the Knox County Health Department, says as many as 40% of rising seventh graders in Knox County public schools last year didn’t get the shots.
"They literally are not able to attend classes because we're trying to avoid outbreaks, so they miss out on their educations," Harrison says.
Harrison says she doesn't think parents are avoiding vaccines as part of a growing movement against immunizations.
"I really do think it's that you just kind of forget about it. You remember when they're little and they start Kindergarten, and now you think you're home free," she says.
Harrison says some parents think about the shots in August - but by then, appointment slots are full around the region. So the department’s asking parents to think about shots as kids get out of school for summer vacation - instead of when they come back.