Summary of the National Advisory Committee on Immunization (NACI) Statement-Updated guidance on Imvamune in the context of a routine immunization program.

Background: Mpox is a viral illness related to smallpox. It can cause flu-like symptoms and a rash, and in severe cases, can lead to hospitalization or death. The Imvamune® vaccine offers protection against mpox. Consistent with global trends, mpox cases in Canada have been reported primarily among men who have sex with men (MSM), with sexual contact as the predominantly reported mode of transmission. While the incidence of mpox in Canada has significantly declined since the fall of 2022, mpox remains an important public health concern with the potential for future resurgence. Methods: The National Advisory Committee on Immunization (NACI) reviewed available evidence on the clinical benefits and risks of Imvamune. This evidence included studies assessing the vaccine effectiveness estimates from real-world evidence, as well as pre- and post-market licensure safety data. NACI has also considered additional factors including ethics, equity, feasibility and acceptability. Guidance on the use of Imvamune in the context of international travel was developed in collaboration with the Canadian Committee to Advise on Tropical Medicine and Travel (CATMAT). Results: NACI concluded that available evidence supported the vaccine's effectiveness and safety in preventing mpox infection. Conclusion: Building on previous interim guidance from NACI recommending the use of Imvamune for pre-exposure vaccination in the context of ongoing mpox outbreaks, NACI now recommends that Imvamune be used in the context of a focused routine immunization program. Individuals at high risk of mpox, including MSM who meet high-risk criteria such as having more than one sexual partner, should receive two doses of Imvamune administered by subcutaneous injection at least 28 days apart.