Ontario to provide second dose of monkeypox vaccine
Ontario will administer a second dose of the monkeypox vaccine to those most at risk of contracting the disease, following new recommendations from a federal panel of experts.
The Imvamune vaccine has been approved by Health Canada as a two-dose vaccine, given 28 days apart, but so far most people at high risk have only received a first dose, mostly in due to limited supply.
The National Advisory Committee on Immunization (NACI) recommended in an updated guidance document released Friday afternoon that those most at risk receive both doses « when the vaccine supply is adequate. »
Although national supply remains limited, NACI also recommends that these second doses can be administered in such a way that only one-fifth of the vial is used per person.
The deployment of the second doses in Ontario should take place soon.
The Ontario Ministry of Health is « reviewing NACI guidance and will work with local public health units on the administration of second doses, » the ministry told The Star.
Those most at risk are men who have sex with multiple male partners, as well as sex workers and staff at « on-site sex venues, » the NACI said.
The number of weekly cases of monkeypox reported during this year’s unprecedented global outbreak continues to fall, the director-general of the World Health Organization told a news conference last week.
There have been 667 reported cases of monkeypox in Ontario, all but five in men.
Symptoms of monkeypox can include fever, swollen lymph nodes, and painful lesions. Most people recover within a few weeks without treatment, but infections can lead to hospitalization.
NACI’s guidance document states that its recommendations are based on factors such as the epidemiology of ongoing Canadian and international epidemics, growing evidence of the level of protection provided by the vaccine, and current and projected supply.
A NACI representative was unavailable for an interview on Monday.
Anecdotally, there have been a few mild cases of monkeypox in people who received a dose of the vaccine, said Dr. Isaac Bogoch, an infectious disease physician in Toronto.
« You probably get better protection having two doses versus one, and I’m totally speculating, but we’ll probably see fewer breakthrough cases with two rather than one, » Bogoch said.
“Let’s nip this in the bud…We have the tools and the capacity to eliminate monkeypox in Canada, and that will help us.
Bogoch said the epidemic is « significantly declining » in Canada.
“The cases are very low right now, (but) it hasn’t gone away,” he said.
“I think we have to be aware that we may see imported cases from other parts of the world where monkeypox has not been found before, but in terms of new cases in Canada, we are in a much better situation now than where we were, for example, in July.
In Canada, the vaccine is currently injected « subcutaneously », that is, into the fatty tissue just under the skin. NACI recommends that second doses can be given as an « intradermal injection », that is, between the layers of the skin, which requires about one-fifth of a dose.
An intradermal dose « should elicit a similar immune response to a full dose administered subcutaneously, » NACI said. « It can take time to train vaccinators in the intradermal technique, which can be done while the first doses are being distributed. »
The recommendation does not apply to high-risk individuals who are also immunocompromised, who NACI says should be prioritized to receive two doses at least 28 days apart.
The intradermal technique, typically in the forearm, is already used to vaccinate against monkeypox in the United States, where supply is also limited. The method has been used with some other vaccines, Bogoch said.
« It’s not hard to do, you just need a special needle, and it’s relatively painless, » he said. « It’s an interesting concept because you can boost the immune system to the same degree using a smaller dose of vaccine in times when the vaccine is limited. »
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