HOUSTON (AP) — State figures show the number of Texas parents refusing to have their children vaccinated for non-medical reasons rose nearly 9 percent last school year.

The Houston Chronicle (http://bit.ly/2aVzYNS ) reported Sunday that nearly 45,000 Texas children were not vaccinated due to "conscientious exemption." That compares to about 3,000 children opting out in 2003, when Texas began allowing vaccination exemptions.

Texas, with about 5.5 million schoolchildren, is among 18 states allowing waivers of vaccine requirements based on conscience or personal beliefs. Children heading to school are required to receive immunizations against illnesses such as polio, measles and mumps.

Critics of vaccination exemptions have raised concerns about the re-emergence of diseases such as measles and whooping cough.

Opponents say they're protecting their children by avoiding vaccines.

Public health officials say vaccines are safe.