By 1998–1999, all but four U.S. states required vaccines for students entering kindergarten through 12th grade, while 30 states required vaccines for students entering college for the first time.
Notes on verification
K-12 figure (all but four states) is well corroborated by an independent source and aligns with Mayo Clinic data; the 30-states-for-college figure remains unverified by independent sources, lowering overall confidence slightly.
Sources
- Vaccine requirements and vaccine research highlights - Mayo Clinic (mayoclinic.org)
- https://auburnexaminer.com/history-of-vaccine-mandates-in-the-us/ (auburnexaminer.com)
- https://www.sciencedirect.com/science/article/abs/pii/S0264410X9900290X (sciencedirect.com)