The Board of Health unanimously approved a measure requiring flu shots for children in city preschools and daycare centers yesterday, enraging some autism activists.

The new law mandates that children between the ages of six months and 5 years of age enrolled in city-licensed preschools and daycare centers receive flu shots by the end of 2014. City schoolchildren are already required to receive vaccinations against measles, mumps, chicken pox and whooping cough; officials say young children are particularly prone to the flu, and the symptoms can be dangerous for their developing immune systems.

"Young children have a high risk of developing severe complications from influenza,” the board said in a statement yesterday. “One-third of children under five in New York City do not receive an annual influenza vaccination, even though the vaccine safely and effectively protects them."

But autism activists who believe childhood vaccinations affect the disorder argue that the city has no right to mandate the vaccine. "They basically rubber-stamped it with very little public participation,” John Gilmore, the executive director of the Autism Action Network, told the Post. “To force someone to modify their children’s body is very, very serious.”

Parents are permitted to forgo the vaccinations for medical or religious reasons, and some families have voiced approval for the measure. “I’ve seen cases of the flu progress in three to four days to death, and it can be very sad," Melanie Butler, a nurse who has an 18-month-old daughter, told PIX 11. "This can happen in previously healthy children." Last year, at least 165 children died of the flu in the United States, and studies have shown no correlation between the flu vaccination and autism, though parental concerns continue to linger.