A handful of students were sick with what Dr. Robert Schirmer, medical director at the Barry-Eaton District Health Department, calls a "break-through" form of chicken pox. It's a milder form that strikes people who have been immunized.
The first outbreak began in November at Sunfield Elementary School in Sunfield. The second is still going on at Page Elementary in Middleville.
Schirmer says in nearly every case, the sick students had one, but not two rounds of vaccines against chicken pox.
In August, the government began recommended a second round of the vaccine. Schirmer says these cases are evidence that recommendation is necessary. The one vaccine is between 80 and 90 percent effective. The second vaccination increases that effectiveness to 98 percent.