As the number of confirmed cases of monkeypox continues to rise in Canada, infectious disease and public health experts provide vaccines to those at risk of infection.
Because both monkeypox and smallpox are part of the orthopox virus family, experts say some vaccines will work against both.
But the vaccines recommended for use against monkeypox today are different from those used in global efforts to eradicate smallpox in the last century, says the World Health Organization (WHO).
“Some countries support the strategic supply of older smallpox vaccines from the Smallpox Eradication Program (SEP), which ended in 1980,” they said. WHO Interim Guideline for Vaccination against Monkeypox issued on Tuesday.
“These first-generation vaccines stored in national reserves are not currently recommended for smallpox because they do not meet current safety and production standards.
Monkeypox causes flu-like symptoms and skin lesions and is spread through close contact.
Both the WHO and Canada National Immunization Advisory Committee (NACI) has already published guidelines on what vaccine to use against monkeypox and who can benefit from it.
What monkeypox vaccine is available in Canada?
The vaccine approved for immunization against monkeypox in Canada is MVA-BN, or Modified Vaccinia Ankara – Bavarian Scandinavian. Bavarian Nordic, based in Denmark, is the company that manufactures it.
In Canada, the vaccine has the trade name Imvamune. (Called Imvanex in the European Union and Jynneos in the United States)
Imvamune was originally authorized in Canada for “emergency use” against smallpox in November 2013, as part of the federal government’s emergency plan to immunize people if the deadly disease ever reappears. In 2020, Canada has extended the vaccine’s permit to include immunization against monkeypox, according to NACI documents.
An employee of the vaccine company Bavarian Nordic works in one of its laboratories near Munich, Germany, on May 24. The company’s Imvamune vaccine is approved in Canada for immunization against monkeypox. (Lucas Bart / Reuters)
Routine smallpox vaccinations stopped in Canada in the early 1970s. But because the viruses are linked, these smallpox vaccinations may have provided some immunity to monkeypox, experts say.
“Probably this, you know, mass smallpox immunization campaign has really kept monkeypox under control for many years,” said Dr. Isaac Bogoch, an infectious disease specialist at Toronto General Hospital.
But most people under the age of 50 in Canada have not received this protection – and that may be one of the reasons we see monkeypox now, he said.
How is Imvamune different from the old smallpox vaccine?
Imvamune contains a weakened strain of the vaccine virus that provokes the immune response to fight smallpox and monkeypox.
Unlike the original smallpox vaccine, this weakened virus does not replicate, which means that it cannot make copies of itself.
Early-generation vaccines based on replicating strains of the vaccine have led to unpleasant side effects for some and could be problematic for people with weakened immune systems, said Dr. Zane Chagla, an infectious disease specialist at McMaster University in Hamilton.
In addition, older generations of smallpox vaccines are administered differently. Instead of a simple syringe, the healthcare provider uses a “split needle” with two teeth and prick the skin repeatedly to enter the dose.
Who should consider vaccination against monkeypox?
Infectious disease experts say that smallpox does not currently affect most of Canada’s general population, although anyone can become infected with the virus if they are in close physical contact with someone who is infected.
The LGBTQ community, especially men who have sex with men, is at a disproportionate risk of infection in this outbreak, they say. Healthcare professionals or laboratory workers who work directly with orthopoxviruses may also be at risk.
As a result, experts say that smallpox vaccinations should be offered to these at-risk populations as a preventative measure. The vaccine can also be offered to those who have already been exposed to someone with monkeypox – known as post-exposure prophylaxis.
In both cases, immunization against monkeypox should be targeted, they say.
“This is not a widespread vaccine for everyone; it’s a risk-based vaccination, “Chagla said.
Bogoch agreed.
“I don’t think we’re close to starting, you know, vaccine campaigns for the general public,” he said.
“At this point, this should be a very focused and targeted vaccination campaign for people who have been exposed and for people who are at the highest risk of getting this infection.
How many doses?
Both the WHO and the NACI recommend two doses of Imvamune given at 28-day intervals.
A possible exception, according to NACI guidelines, is someone who has had smallpox vaccination in the past. In this case, they can only be given one dose to act as a booster.
Are there any potential allergens in the vaccine?
Yes. NACI says Imvamune includes the following ingredients:
-
Traces of DNA and protein of the residual host cell (eggs).
-
Tromethamine (Trometamol, Tris).
-
Benzonase.
-
Gentamicin and ciprofloxacin.
Add Comment