PHOENIX - Children lined up at five Valley elementary schools Monday as Maricopa County began a drive to vaccine thousands of kids against the swine flu.

"This is our opportunity to get enough children vaccinated so that the disease doesn't have a chance to spread in our community as we go forward," said county health director Dr. Bob England.

He said ideally, all students will be vaccinated by winter break.

England said the process of dealing with the federal Centers for Disease Control on supplies of the vaccine is one of the most frustrating experiences of his life. By now, the county should have received about 400,000; it has received only about 150,000, he said.

"We've had to put off these school clinics for more than a couple of weeks in order to try to get more to the sickest kids first," said England. "But, we have to start now."

The first schools to have the vaccine were Littleton Elementary in Avondale, Queen Creek Elementary, Desert Springs Elementary, Jacobsen Elementary in Chandler and Sonoran Sky Elementary.

About 80 elementary schools have been placed on a priority list and will hold clinics in the next two weeks, officials said.

"This is only for the children of the schools... The times will be unique to the schools, but it will be during the school day," said John Roehm, CEO of Mollen Immunization Clinics.

He added, "The students have pre-registered. We will rotate the students in. We'll have maybe anywhere from six to nine nurses, maybe more, depending upon the size of the school."

At Desert Springs Elementary, 73 students were pre-registered to receive the vaccine of about 380 who were eligible.

Most health insurance plans cover the swine flu shot, Roehm said. For those who have no insurance, the cost is $15. But, Roehm said students will not be turned away if their parents cannot pay.

Karen Neyer brought her fourth grade daughter to school at Desert Springs. She said she had mixed feelings about the swine flu vaccine, but that she wanted her daughter to be safe.

"She's getting both the flu and swine flu vaccine," Neyer said.

Student Blake Moler was not getting a shot Monday, but said he will eventually.

"I think it's a good thing for the school that they're giving swine flu shots because some people could get sick," he said.

Health officials say as many as 5.7 million Americans have been infected with swine flu during the first few months of the pandemic.

Scientists at the Centers for Disease Control and Prevention estimate that between 1.8 million and 5.7 million Americans were infected from April through July. The estimate is the CDC's most specific calculation to date. Officials had simply been saying millions have been infected.

For more information on the school clinics, visit www.flushotsusa.com.

(Copyright 2009 Bonneville International Corporation. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. AP contributed to this report.)