April 4, 2017

Measles is a virus of the family Paramyxoviridae that is spread via the airborne route and also through coughing, sneezing and direct contact with respiratory secretions. It is one of the most infectious viruses known with a reproductive rate of 12 to 18 per cent in fully susceptible populations.

Measles infection is uncommon in Toronto with a five year average of three cases per year reported to TPH. Most of these cases are the direct result of travel. However, from time to time, local outbreaks of measles infection occur.

In Ontario, one dose of a combined measles, mumps, rubella (MMR) vaccine is currently given on or after the first birthday followed by a second dose at four to six years as MMRV (combination vaccine – MMR with varicella). Most schools have vaccination rates of 90 per cent or more.

A cohort of individuals born between 1970 and 1992 may not have received two doses of the MMR vaccine. Those born before 1970 likely had natural infection and are considered immune (except for health care workers who are not considered immune by age and require either proof of two doses of vaccine or serology showing measles immunity).