ALTOONA, Pa. -- A mass H1N1 immunization effort began Monday for students in the Altoona Area School District.

The vaccination clinic has been in the works since the summer, when school district nurses attended a Webinar to get the latest information concerning the H1N1 virus. The nurses will travel to each school through next Tuesday to administer the vaccine in both the injection and nasal spray forms.

More than 2,500 Altoona Area School District students are expected to receive the vaccines. The district's spokesman said the vaccination effort is the biggest undertaking he's seen in the school district in more than 20 years.

The vaccines were provided through the Department of Health. Students under age 10 will receive a second dose of the vaccine within 21 days after their first dose and those will also be administered through the school's clinics.