There have been no confirmed cases yet, but attendees should look out for symptoms until April 30.
Another person who tested positive for measles attended Nga Taiatea Wharekura School while infectious.
The first symptoms of measles are fever, runny nose, sore runny eyes, a cough and, later on, a rash.
Of the eight confirmed cases, all patients were treated in the Waikato Hospital Emergency Department.
Three required hospitalisation, but have been since discharged.
The measles virus is highly infectious and can be very serious. It is spread by tiny droplets in the air and is one of the few diseases that can spread easily to those nearby.