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Doctors in Toronto are responding to a small measles outbreak in which four people – three of whom had not received their measles vaccine – were diagnosed with the infectious disease in less than a week. Health officials announced on Monday that tests confirmed infections in two adults and two children under the age of 2. One case was confirmed on Jan. 29, two on Jan. 30 and one on Feb.1. Public-health officials have not been able to find any connections between the four patients, nor have they been able to determine where they contracted the virus.

A brief history of the measles vaccine

Pre-1954

In pre-vaccine era, epidemics occurred frequently. Infection was almost universal. In Canada, measles was responsible for 400 cases of encephalitis and 50 to 75 deaths annually. In the U.S., 3 to 4 million people were infected each year, an estimated 4,000 suffered encephalitis and 400 to 500 people died.

1954-63

Measles virus is isolated and a vaccine developed.

Since 1963

Number of cases declines by 99 per cent (from approx. 350,000 per year before 1963 to less than 2000 per year in 1995.)

1995

A brief flare up was reported in Canada, leading to a two-dose immunization regimen. Some provinces and territories launched catch-up vaccination campaigns.

1998

Canada institutes a national, active measles surveillance program. All provinces and territories report confirmed cases of measles weekly to the Public Health Agency of Canada, which in turn reports weekly to the Pan American Health Organization.

With files from Kelly Grant
Sources: U.S. Center for Disease Control, Health Canada, Immunization Canada