The reporting of measles cases in the National Capital Region has put the spotlight on parents who decide not to get their children vaccinated, but an Ottawa researcher says the limited spread of the virus suggests current immunization policies are containing it.

On Saturday, Ottawa Public Health confirmed two children and one adult are being treated for measles.

The three either were not vaccinated, or did not have complete vaccinations in Ottawa and Lanark County.

Health officials confirmed the virus was brought to the region by a patient who had travelled internationally, but for privacy reasons, the department won't disclose where that person travelled.

There have been no new cases since.

High vaccination rate

Dr. Kumanan Wilson said the fact measles has not spread to more people suggests the vaccination rate among the general population is close to the 95 per cent threshold that provides "herd immunity."

"We haven't seen the sustained spread, which suggests that vaccination rates are pretty good and are preventing the spread," the Ottawa Hospital researcher says.

In 2014, measles spread from a single case of an unvaccinated child who contracted the illness while travelling in the Philippines. A total of four cases were reported that year.

Dr. Kumanan Wilson, an Ottawa researcher, said the fact measles reported in the Ottawa area has not spread to more people suggests the vaccination rate among the general population is close to the 95 per cent threshold that provides 'herd immunity.' (CBC)

In most years, there are no measles cases in Ottawa. Wilson said the number depends on how many non-immunized people are exposed to the virus.

"In a totally unvaccinated population, for each individual that gets measles, 12 to 18 other individuals will get the condition," he said.

"That makes it one of the most infectious conditions we know of. The likelihood of spread is totally dependent on the immunization coverage they're surrounded by."

Mandatory immunization might not solve problem

Wilson said it's important that people recognize vaccines are effective and safe. People who can get vaccinated, should.

"People need to be immunized not only to protect themselves, but to protect others," Wilson said.

It's a sentiment shared by Ryan Knuth, whose two-month-old son Theo recently spent five days at Children's Hospital of Eastern Ontario (CHEO) after developing a fever.

Ottawa Public Health called Knuth on Friday to let him know that Theo — who is too young to be fully immunized against measles — may have been exposed to the virus that causes the disease.

"If you decide not to vaccinate your child, it's affecting others. And it can and will affect others," Knuth said. "Right now, my son is at home, at risk of severe complications — potentially even death — because of exposure to measles."

Health Canada recommends the first dose of the measles vaccine be administered at 12 to 15 months old. It also recommends people with compromised immune systems not receive live vaccines.

The agency says people with severe acute illnesses should postpone receiving the vaccine.

Symptoms of measles include fever, runny nose, coughing and a red, blotchy rash after the fever appears. Complications can include hearing loss, pneumonia, brain swelling and even death.

Ryan Knuth's two-month-old son Theo recently spent five days at the Children's Hospital of Eastern Ontario, where he may have been exposed to the measles virus. Theo is too young to receive the vaccine. 'If you decide not to vaccinate your child, it's affecting others. And it can and will affect others,' Knuth said. (CBC)

Wilson said the current policy on immunization may work better than excluding children from school if their parents object to shots for "philosophical reasons."

Public health officials are required to keep track of students' immunization records and can exclude children who have been exposed to the virus but don't have up-to-date shots.

Wilson said a more restrictive policy could make outbreaks worse.

"The risk of making it mandatory is that some parents may choose not to send their children to school and home school them, or put them in an alternative school system, in which case you get clustering groups of unvaccinated children, and that increases the risk of an outbreak substantially."

Ottawa Public Health said the immunization rate among Ottawa's school-age children is 98.4 per cent.

Associate medical officer of health Dr. Carolyn Pim said fewer than 10 children have been excluded from school in the current outbreak. She said the children will be assessed on a case-by-case basis to determine when they can return to classes.

Immunization proof should be required: CMA

The Canadian Medical Association said proof of immunization should be required for all children attending licensed daycare or school in all provinces.

In a written statement, CMA president Granger Avery said the association is concerned misinformation is creating doubt among some parents about the value of vaccines.

"The CMA is encouraging all provinces to establish immunization registries so that health-care workers have a better understanding of immunization levels in Canada to ultimately prevent a situation like the one currently unfolding [in Ottawa and Lanark County]," he said.