P.E.I. health officials are taking note of a number of breakthrough cases of chicken pox in Queens County, but they expect the number of cases to fall dramatically in coming years.

Carson Harding is home from school with chicken pox, despite being vaccinated. (CBC)

Carson Harding of Stratford was home from school Wednesday with chicken pox. His little brother got it first, then his older sister.

"I woke up this morning and I was eating and I started scratching and my mom said, like 'What's going on,' and I said 'I don't know,' and then she's like 'Oh God, you've got the chicken pox.'"

Like many people, the Hardings thought their kids were immune. They all received the vaccine when they were little. The province started offering it in the year 2000. Carson's father Rob Harding discovered with a little research that chicken pox is not uncommon in children who have been vaccinated only once.

"When we investigated it, it was like, yeah they've got their shots, but, there's still a chance they can have the chicken pox," said Harding.

"Sure enough, three out of three."

The Harding kids only got one dose of the vaccine. That's the way the program worked at the time. Carson and his brother and sister got what are called breakthrough cases.

Breakthrough cases of chicken pox are typically less severe, says Chief Public Health Officer Heather Morrison. (CBC)

"Breakthrough cases tend to be much more mild than the full on varicella," said Chief Public Health Officer Dr. Heather Morrison.

"Children are feeling not as sick, and they don't have as many spots."

Breakthrough cases aren't unusual, and tend to happen in different parts of the Island each year, and Morrison said it seems to be Queen's County's turn this year.

In 2011, the National Advisory Committee on Immunization recommended the chicken pox vaccine change to two shots, instead of one, to boost immunity. Since then, Island children going into kindergarten have also been offered the second dose.

"We know now that this booster dose of varicella makes the vaccine almost 100 per cent effective. It will really have better coverage with that booster dose," said Morrison.

Morrison said when a case is reported, public health nurses make sure people who've come in contact with those who have chicken pox are offered the vaccine as well, to protect them and keep it from spreading.

Carson will miss a few more days of school while he recovers, and he is not looking forward to the time off.

"Stomach aches, you get Tylenol and you're back out there in a day," he said.

"Chicken pox you stay home for a week and you just sit and get bored to death."