AUSTIN, Texas -- Texas could be the epicenter for the nation's next major fight over stricter requirements for immunizations as rates of schoolchildren who refuse shots for non-medical reasons climb in America's second-largest state.

The number of Texas kindergarten through 12th grade students who reported filing conscientious exemptions for at least one immunization last school year increased 19-fold since 2003 -- though that is still less than 1 percent of enrolled students, according to the Immunization Partnership, a pro-vaccination Texas not-for-profit.

Texas requires parents to approve immunizations rather than mandating shots and having families opt out if they object to them.

Some Texas state lawmakers said Wednesday they want to create a system where students who oppose immunizations would have to opt out of otherwise standard immunizations and could only do so after watching a video on the medical effectiveness of vaccines.

The most common immunizations protect against measles, mumps and rubella, or German measles, as well as diphtheria, tetanus, whooping cough, polio and hepatitis A and B.

Texas and 17 other states allow philosophical exemptions to vaccines.

California used to let students forgo vaccinations for similar reasons -- only to approve some of the country's strictest vaccine requirements last year. That law eliminated religious and personal beliefs as reasons for opting out of mandatory immunizations.

The small group of Texas lawmakers that wants to make changes isn't planning to go that far when the GOP-controlled Legislature heads back into session Jan. 10.

"The fact is that people have a choice to not immunize, but we need the herd effect," Rep. Donna Howard, an Austin Democrat who has filed an immunization "opt-in" bill, said Wednesday. "We need a significant number to be immunized to not only protect themselves, but to protect the larger community."

Past efforts to improve immunization rates in Texas mostly have been stymied by opposition from conservative legislators who are immunization skeptics, as well as a political group called Texans for Vaccine Choice.

They point to discredited studies linking immunizations to health problems including autism.