In the U.S., children receive the first recommended dose of measles, mumps and rubella (MMR) vaccine
between 12 and 15 months of age; in Canada, the first dose is recommended at age 12 months.
A new study in the November 2013 Pediatrics (published online Oct. 21) found children in Canada who had received their first dose of MMR vaccine at age 15 months had a higher level of immunity to measles than children who received their first dose at age 12 months.
In the study, “Measles in Children Vaccinated with 2 Doses of MMR
,” Canadian researchers sought to confirm findings from a high school measles outbreak, in which a significantly higher number of children who had received their first of two MMR vaccine doses at age 12 to 13 months contracted measles, compared to children who received their first MMR vaccine at age 15 months or older.
The study authors identified 102 measles cases in Quebec children, ages 5 to 17, between Jan. 1 and Dec. 31, 2011. For each measles case, they randomly selected five matching controls (for a total of 510 controls) from the provincial measles vaccine registry. Eighty-nine percent of the measles cases were diagnosed in children ages 13 to 17. When the first MMR dose was administered at 12 to 13 months, the risk of measles was six times higher outside the outbreak school than when the first MMR dose was given at age 15 months or older. After adjusting for age at second MMR dose, gender and mother’s year of birth (1970 marks the first year of measles vaccines in Canada), the risk was 5.2 times greater in children from the outbreak school, as well as in children attending other schools.
The study authors recommend further evaluation of the recommended age for the first MMR dose.