Measles Cases Linked to Unvaccinated Mothers in Ontario
Six infants born to unvaccinated mothers in Ontario have been diagnosed with congenital measles since the onset of a significant outbreak late last year. This situation is noted as the largest outbreak of the disease in the western hemisphere.
Kieran Moore, the province’s chief medical officer of health, reported that these infants, who contracted measles while in the womb, have fully recovered. He emphasized that routine vaccination could have prevented these infections.
Congenital measles is when a child is born already infected with this highly contagious virus, which can lead to severe complications, including brain inflammation and, in some cases, death.
In 1998, Canada was recognized as having achieved “elimination status” for measles, indicating the virus was no longer circulating regularly. However, the current outbreak in Ontario raises concerns about reversing that status.
Since October, Ontario, which is Canada’s most populous province, has reported over 2,000 cases—surpassing the total number of cases in the United States for the year 2025.
Despite measures to control the outbreak, public health data show continuing increases in cases. Recently, the situation worsened with the province recording its first fatality: a premature infant who contracted measles in utero and succumbed to related medical issues.
“It’s only a very small subgroup of people who have chosen not to get vaccinated who are having the complications,” Moore remarked.
Although the vaccine is not advised during pregnancy due to its live virus content, public health advises unvaccinated pregnant individuals to receive one dose of intravenous immunoglobulin if they come into contact with measles.
“Some folks might decline the vaccine, and they might also refuse the immunoglobulin, which could be a philosophical decision,” he added.
Moore pointed out that Canada’s high vaccination rates have mitigated what could have been a much more severe outbreak, offering significant protection to large portions of the population.
“I know some will focus on the negatives. To have that level of protection against global risks is, I think, quite an achievement,” he noted.
