A New Jersey state law requiring young children attending licensed pre-school and child care centers to get flu vaccinations will be tested as thousands of children return to classrooms after the holiday break.

New Jersey is the first state in the nation to require flu shots for young schoolchildren. The state set a December 31 deadline for parents to obtain flu vaccinations for their children, part of a new policy requiring a total of four additional immunizations for schoolchildren. The policy was implemented over the objections of some parents who worry about possible risks from vaccinations.

Health officials said they would not know until after the holiday how many children have met the requirement. Children who have not received the flu vaccine are to be barred from attending.

The New Jersey Coalition for Vaccination Choice held a rally in Trenton that drew hundreds of parents who said they should be the ones to decide if their children need flu shots, not the state.