LINCOLN (AP) – Six students in Lincoln have been diagnosed with chickenpox, and five others have been barred from classes because they haven’t been vaccinated.

School Administrative District 67 Superintendent Michael Marcinkus said three siblings were identified this week as having chickenpox, bringing the total to six.

Officials sent a letter to parents seeking vaccination records or medical histories. Students who can’t show they’ve been vaccinated or have had chickenpox could be barred from school for up to 16 days, as required by state law.

Chickenpox is a disease caused by an infection that results in a fever and an itchy rash.