Seven residents at the Maimonides Geriatrics Centre in Côte Saint-Luc, who were among the first in the province to receive the COVID-19 vaccine, have now tested positive for the virus.
A letter sent to family members said the residents were infected within the first 28 days after their first dose. The residents were from the 4th, 5th and 7th floors. The centre did not release details on the conditions of the residents who have contracted the virus.
To date 80 per cent of nursing staff and 84 per cent of residents at Maimonides have received their first dose of the vaccination. Residents were scheduled to receive their second dose last week, but the Quebec government decided to delay the second jab in an effort to vaccinate as many people as possible.
The province started administering the Pfizer-BioNTech vaccine on December 14.
According to Pfizer Canada, protection against COVID-19 begins as early as 12 days after receiving the first dose, however it is estimated to be just 52.4 per cent effective before the second dose.
A study published in the New England Journal of Medicine found that vaccine efficacy rose to 95 per cent seven or more days after the second dose.
The makers of the two vaccines approved for use in Canada, Pfizer and Moderna, maintain the two doses of their vaccine must be administered at a three-week interval in order to achieve 95 per cent efficacy.
Last week the home's family advocacy group threatened legal action against the provincial government if it did not deliver the second dose of the vaccine to residents.
On Monday the group asked Health Canada to step in and ensure Quebec follows a vaccination schedule authorized by the vaccine manufacturers.
Maimonides said it is working with Infection Prevention Control and Public Health to analyze the situation.