In this Thursday, Jan. 29, 2015 file photo, a pediatrician holds a dose of the measles-mumps-rubella (MMR) vaccine at his practice in Northridge, Calif.
In this Thursday, Jan. 29, 2015 file photo, a pediatrician holds a dose of the measles-mumps-rubella (MMR) vaccine at his practice in Northridge, Calif. Damian Dovarganes AP
In this Thursday, Jan. 29, 2015 file photo, a pediatrician holds a dose of the measles-mumps-rubella (MMR) vaccine at his practice in Northridge, Calif. Damian Dovarganes AP