02/07/2014 04:48 EST | Updated 04/09/2014 05:59 EDT

3 Immunized Calgarians Diagnosed With Measles

ROBYN BECK via Getty Images
Public school student Julio Valenzuela, 11, grimaces as he gets a vaccination at a free immunization clinic for students before the start of the school year, in Lynwood, California August, 27, 2013. Nurses are immunizing children in preparation for the first day of public school on September 3. The clinic offers the mandatory vaccinations for school children against diphtheria, tetanus, pertussis, polio, hepatitis B, MMR (measles, mumps, rubella) and chickenpox . AFP PHOTO / Robyn Beck (Photo credit should read ROBYN BECK/AFP/Getty Images)
Four Calgarians have been diagnosed with the measles this year — of those four, three were fully immunized against the virus. 

Alberta Health Services is warning that the strain of measles appears to be unusual. Health officials are investigating the strain, said AHS's Dr. Judy MacDonald on Friday afternoon.

Between 2000 and 2013, there have been 20 confirmed cases of measles in the Calgary area. Of those, only two cases were confirmed where the person had been immunized, said MacDonald.

Symptoms appear to be milder in those who've been immunized, said MacDonald.

The latest case involves a student around the kindergarten or Grade 1 age from Clear Water Academy, said MacDonald. 

Staff and students at the university prep school that have not been immunized will be send home for a couple weeks. 

The other cases include a 16-year-old student and a 16-month-old infant, both of whom contracted the virus in the Philippines, said MacDonald. The baby is the one who had not been immunized. 

The fourth person with the virus is a 36-year-old, according to MacDonald. 

The vaccination has at least a 95 per cent effectiveness rate, said University of Calgary microbiologist Glenn Armstrong, who is an expert in infectious diseases. 

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