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Ontario shortens AstraZeneca dose interval to eight weeks


Ontarians who received their first dose of the Oxford-AstraZeneca vaccine will be able to get their second dose after eight weeks with informed consent.

The province made the announcement Saturday afternoon. In a news release, the Ministry of Health said the change was made in consultation with the chief medical officer of health and other health experts, including the Ontario Science Advisory Table.

"This decision is based on emerging clinical evidence about the administration of two doses of different vaccines, as supported by the National Advisory Committee on Immunization (NACI)," the ministry said.

"Evidence from multiple studies indicates that mixing of COVID-19 vaccines (receiving an mRNA vaccine after an AstraZeneca vaccine) at dosing intervals between eight and 12 weeks is safe and demonstrates a beneficial immune response."

Starting on Monday at 8 a.m., those who got their first dose of the AstraZeneca vaccine will be eligible to book their second dose appointment at an interval of eight weeks and can choose between the same shot or an mRNA vaccine – Pfizer or Moderna.

The province said residents who want an mRNA vaccine for a second dose can book their appointment through the provincial booking system, while those who wish to receive the AstraZeneca shot for their second dose should contact the place where they got their first jab.

The change comes following calls from public health experts and local politicians to shorten the 12-week dosage interval, allowing more people to be fully vaccinated, especially due to the emergence of the B.1.617.2 variant, also known as the Delta variant.

Studies in other jurisdictions show that having two doses provide better protection against the more infectious variant first discovered in India.

Dr. Isaac Bogoch, an infectious disease expert and member of the province's vaccine task force, said the provincial government made a smart decision in accelerating second doses for people who had AstraZeneca first dose.

"This really enables people to get that second dose in a reasonable time to protect themselves from this Delta variant," he said in an interview with CP24.

"This is the right move."

When asked about informed consent, Bogoch believes the province just wants people to have a talk with a health-care provider before they decide to get their second vaccine at eight weeks.

"I don't think people will really require any form of documentation," he said.

"I don't want to put words in the mouths of the province, but I think many individuals are informed they know exactly what they're doing. We have a very health literate population, especially throughout the course of the COVID-19 pandemic, as people have been following the news extremely closely."

Bogoch said the changes announced Saturday would allow more people in the province to be fully immunized, which will help mitigate the impact of the variant.

"We'll just continue to watch COVID-19 rates crumble in the province. We'll be able to reopen in a safe manner, and we'll slowly return to what we remember as we were in the pre-COVID-19 times. We're not there yet, but we're well on that path."

Brampton Mayor Patrick Brown, one of the local officials who pushed for a shorter dose interval, said in a statement that it is great news for essential workers.

“Residents will now have the choice to be fully immunized sooner so they have better protection against variants,” Brown said. “We need to crush COVID-19.”

Toronto Mayor John Tory also thanked the Ford government for listening to the advice from health experts and “making this change that will lead to more people getting fully vaccinated much earlier.”

“This is good news for tens of thousands of Toronto residents who did the right thing and got their first doses of AstraZeneca as soon as they were eligible earlier this year,” Tory said.

The co-chair of the science table said Thursday that while the Delta variant will soon become dominant in the province, its spread can be controlled and avoid a fourth wave surge as long as second doses are accelerated in hot spot neighbourhoods dealing with variant cases.

"This is not a doomsday scenario. We believe that if we are able to really continue a high-risk community-focused vaccination strategy and do that really quickly and expeditiously, we have a good chance of controlling the Delta variant and actually a really good chance at a good summer," said Dr. Adalsteinn Brown.

Earlier this week, the province expanded the eligibility for second doses in Delta hot spot regions. People living in those seven areas, which include Toronto, Peel Region, and York Region, who received their first mRNA dose on or before May 9 will be able to book their second dose starting on Monday, June 14. Top Stories

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