The measles outbreak in the Saint John region has grown to 12 confirmed cases and has spread to Hampton High School, the department of health has confirmed.

The previous 11 cases have been linked to Kennebecasis Valley High School in Quispamsis and the Saint John Regional Hospital's emergency department. The new case at Hampton High is linked to the cases at Kennebecasis Valley High School.

Anyone present at Hampton High on May 30 or 31 may have been exposed to the highly contagious respiratory disease, the letter sent home to parents on Friday night from New Brunswick's deputy chief medical officer of health Dr. Cristin Muecke states.

She estimates about 18 of the approximately 600 students "could be vulnerable."

Dr. Cristin Muecke, deputy chief medical officer of health for New Brunswick, said students will be allowed to sign their own immunization consent forms because of the short notice about Sunday's clinic. (CBC)

Chief medical officer of health Dr. Jennifer Russell says public health has been in direct contact with those potentially exposed to the disease.

Measles is transmitted by direct contact with an infected individual or through the air, with infectious respiratory droplets lingering for up to two hours after the contagious person leaves an area.

Clinic not for family members or public

Public Health will hold a special vaccination clinic at Hampton High School on Sunday from 10 a.m. until 5 p.m. for students and staff only.

If the measles, mumps, rubella (MMR) vaccine is administered within 72 hours of possible exposure, it can provide retroactive protection, regardless of previous immunization history.

Anyone who is pregnant or has a compromised immune system should not receive a live vaccine. They are advised to stay away from the school until Public Health can give further advice.

"Those close to you, including family members, are not considered to have had a potential exposure unless otherwise notified," and should not attend the clinic, wrote Muecke.

"For safety and security reasons, this clinic is not open to the public. Please do not distribute further beyond the school community."

Anglophone South School District superintendent Zoë Watson said today the school is connecting with anyone who was in Hampton High on Thursday or Friday.

"This includes members of district staff, partners and special guests who were at the school for an activity yesterday," Watson said in an email.

The school gym has been set up for the clinic tomorrow.

Vaccine supply reserved for most vulnerable

Public Health is reserving its vaccine supply for those most at risk during the outbreak — infants and people who have had direct contact with somebody with measles.

"We need to protect our vaccine doses for those that we know came into contact with a case," Russell said.

One dose of the measles, mumps, rubella (MMR) vaccine is about 85 per cent effective, while two doses offer about 97 per cent protection, according to health officials. (Submitted)

She confirmed there is enough vaccine for the outbreak, and the department is in contact with national health officials to make sure there is adequate supply.

It's unclear how many more people have potentially been exposed through the Hampton case.

Earlier this week, health officials said more than 2,000 people were potentially exposed through the nine cases linked to Kennebecasis Valley High School and two ER-related cases.

The Hampton case is the first new confirmed case since Tuesday, but on Friday Russell announced another possible point of exposure related to a previously announced case.

Vet's Taxi users take heed

People who used Vet's Taxi last week may have come into contact with the virus, she said.

Russell didn't release any information about the infected individual, but Vet's co-owner Shelley Orr told CBC News it was a passenger, not a driver.

The dates and times in question include:

May 22 from 8 p.m. to 11:30 p.m.

May 24 from 9:40 a.m. to 1:30 p.m.

May 25 from 2:45 p.m. to 5 p.m. and 6:40 p.m. to 9:10 p.m.

May 26 from 12:50 p.m. to 3:05 p.m.

It's too late for anyone potentially exposed in that case to get a vaccine because more than 72 hours have passed, said Russell.

She is advising them to self-monitor for measles symptoms, which can take up to 18 days to begin.

"If you are experiencing symptoms stay at home and self-isolate. Do not go to the ER, community health clinic or doctor's office, call Telecare 811."

Hampton High School has 543 students and 44 staff, according to its website. (Google Street View)

Early symptoms may include fever, cough, runny nose, red or sore eyes, sleepiness, irritability and tiny white spots in the mouth.

About three to seven days after those symptoms start, the telltale red blotchy rash usually develops on the face and then spreads to the rest of the body.

Since October 1995, all children born in New Brunswick have been offered two doses of the MMR vaccine, which is generally about 97 per cent effective, Muecke said in her letter to Hampton High parents, guardians, students and staff.

"However, a small number of individuals could become infected if they have been exposed to an active case," she said.

"In a school of 600 students this could potentially mean that about 18 students could be vulnerable."

Vaccination rates unknown

But Education Minister Dominic Cardy has said the province doesn't know how many unvaccinated students are in the school system because the school districts have not been consistently enforcing proof of immunization requirements.

Anyone who has already had two doses of MMR can safely get a third, said Muecke. Individuals who have received the MMR or another live vaccine within the past month should not, however.

Students and staff who have not received a dose of MMR in the last 28 days will be contacted by Public Health to arrange to have blood drawn to determine their immunity to measles, she said.

"If the results are negative or borderline, or if the required information for the student is absent, Public Health may exclude them from the school for 21 days to contain the outbreak."

Hampton High's online calendar shows exam week is scheduled to start on June 10 and prom is on June 17.

"I am certain some of you will have questions regarding the clinic, and what a case of measles means for our students as we close out the school year," principal Rosemary Southard wrote in an email to parents, students and staff.

Classes and activities are continuing as usual, she said.

"Should Public Health deem it necessary for any student to remain at home, we will ensure that supports are made available."

Hampton High has 543 students and 44 staff, according to its website.

People born before 1970 are considered immune to measles and anyone who has already had it is considered protected for life.

Measles can be severe in infants and adults born after 1970. Complications can include ear infections, pneumonia, blindness and swelling of the brain, which can cause seizures, deafness, brain damage or death.

If contracted during pregnancy, it can cause miscarriage, premature labour, and low birth weight.

The first confirmed case of measles in the region, announced on April 26, was an individual who had recently travelled to Europe and visited the Saint John Regional Hospital's emergency department before being diagnosed.

Possible exposure times at the ER include: