Mpox vaccine is 58% effective after one dose, Canadian study finds
Global News
A new study finds that a single dose of the mpox vaccine offers 58 per cent protection against the virus, providing promising evidence for its effectiveness in real-world settings.
A single dose of the mpox vaccine offers moderate protection against the virus, according to a new Canadian study. While “moderate” might not sound impressive, the researchers describe the results as “terrific” and hope more Canadians at risk will continue to get vaccinated.
The study, published Wednesday in the BMJ, found that a single dose of the Modified vaccinia Ankara-Bavarian Nordic (MVA-BN) was 58 per cent effective in protecting against the mpox infection.
No randomized clinical trials have yet been conducted to test the effectiveness of vaccination against mpox. Previous estimates, based on observational studies, suggested that a single dose of the vaccine could be anywhere from 36-per cent to 86-per cent effective, the study said.
“It’s important because prior to the emergency use of this vaccine to try and reduce infections during a global outbreak that also affected Canada, there was no previous clinical trials to tell us how well this vaccine might work in the real world during an outbreak,” said Dr. Sharmistha Mishra, the study’s co-author and associate professor in the Department of Medicine at the University of Toronto.
“We had a lot of data on safety with this vaccine, but not very much data on how well it would work. It was rolled out in an emergency situation, and because of the type of data infrastructure and health-care system we have in Ontario, we were able to finally take a look and see how well it actually worked,” she told Global News.
The vaccine is typically given in a two-dose regimen, 28 days apart, to protect against mpox. However, this study did not examine the effectiveness of the second dose.
The MVA-BN vaccine is a smallpox vaccine introduced after the global mpox outbreak was declared a public health emergency in July 2022.
In Ontario, the vaccine was initially introduced in June 2022 as post-exposure for high-risk contacts and pre-exposure for gay, bisexual, and other men who have sex with men, as well as sex workers at high risk of exposure, the study said.
