Pediatrician Charles Goodman vaccinates 1 year- old Cameron Fierro with the measles-mumps-rubella vaccine, or MMR vaccine at his practice in Northridge, Calif., Thursday, Jan. 29, 2015. Some doctors are adamant about not accepting patients who don't believe in vaccinations, with some saying they don't want to be responsible for someone's death from an illness that was preventable. Others warn that refusing treatment to such people will just send them into the arms of quacks. (AP Photo/Damian Dovarganes)

Amid the measles outbreak stemming from California, the White House is telling parents that science indicates they should vaccinate their children.

President Barack Obama's press secretary says the science on vaccinations "is really clear." Josh Earnest tells journalists that Obama believes vaccination decisions should be made by parents, with a bias toward good science.

About 100 cases of the have been reported in the U.S. since last month in the second-biggest outbreak in at least 15 years. Most have been traced directly or indirectly to Disneyland in Southern California.

Earnest says are closely monitoring the outbreak.

The Centers for Disease Control and Prevention says measles-mumps-rubella vaccine is 97 percent effective at preventing measles.

  • A single-dose vial of the measles-mumps-rubella virus vaccine live, or MMR vaccine is shown at the practice of Dr. Charles Goodman in Northridge, Calif., Thursday, Jan. 29, 2015. Some doctors are adamant about not accepting patients who don't believe in vaccinations, with some saying they don't want to be responsible for someone's death from an illness that was preventable. Others warn that refusing treatment to such people will just send them into the arms of quacks. (AP Photo/Damian Dovarganes)

  • Boxes of single-doses vials of the measles-mumps-rubella virus vaccine live, or MMR vaccine and ProQuad vaccine are kept frozen inside a freezer at the practice of Dr. Charles Goodman in Northridge, Calif., Thursday, Jan. 29, 2015. Some doctors are adamant about not accepting patients who don't believe in vaccinations, with some saying they don't want to be responsible for someone's death from an illness that was preventable. Others warn that refusing treatment to such people will just send them into the arms of quacks. (AP Photo/Damian Dovarganes)