Summary of NACI statement of February 13, 2025: Updated recommendations on measles post-exposure prophylaxis

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• Overview
• What you need to know

Overview

On February 13, 2025, the Public Health Agency of Canada (PHAC) released the National Advisory Committee on Immunization's (NACI) Updated recommendations on measles post-exposure prophylaxis. This guidance is based on current evidence and NACI expert opinion.

• Measles is a highly contagious disease with the potential for severe outcomes, such as pneumonia, encephalitis, and death. Although Canada achieved measles elimination status in 1998, sporadic cases and outbreaks still occur, often among unvaccinated individuals
• In light of recent measles activity in Canada and globally, NACI reviewed recent evidence on human immunoglobulin products and vaccines for measles post-exposure prophylaxis (PEP), including feasibility considerations of their use. Based on this review, NACI provided updated options for PEP that provinces and territories can adapt to meet their specific public health needs.

Following a thorough review of the evidence, NACI has issued the following recommendations:

• NACI continues to strongly recommend completion of the routine childhood and adult recommended immunization schedule with a measles-containing vaccine.
  • High (e.g., >95%) routine measles immunization coverage provides herd immunity protecting people who live in Canada and ensuring Canada remains free of endemic measles.
  • Routine immunization against measles is the best tool to mitigate the size of measles outbreaks and reduce the need for measles post-exposure prophylaxis.
  • In the absence of contraindication to the vaccine, a measles-containing vaccine series is effective in protecting immunocompetent individuals and is a preferred strategy.
• NACI recommends that post-exposure prophylaxis (PEP) following exposure to measles should be offered to individuals not expected to have measles immunity.
• Detailed strategies for measles PEP vary for different populations (e.g., for those who are immunocompromised based on level of immunocompromise, for infants, and for use during pregnancy). Please see the full NACI statement for further details.
• As measles epidemiology evolves both globally and within Canada, NACI will continue to monitor emerging evidence and update guidance on measles PEP and other recommendations on measles vaccination as needed.

To receive a PDF copy of the full NACI Statement, please email naci.publications-ccni@phac-aspc.gc.ca. A fully accessible version of the statement will be available online on the NACI webpage and will be incorporated into the chapter on measles vaccines in the Canadian Immunization Guide as soon as possible.

What you need to know

• Measles is an acute and highly contagious infectious disease caused by the measles virus.
• Measles symptoms typically begin with fever, cough, runny nose (coryza), conjunctivitis, followed by a rash that starts on the face and spreads to the body and limbs. In pregnancy, measles increases the risk of pneumonitis, hepatitis and premature labour. For individuals who are immunocompromised, measles can be particularly severe.
• Measles cases continue to occur in Canada, driven by rising global measles activity, reduced vaccination rates, and increased international travel. When measles exposures or outbreaks occur in Canada, public health authorities follow the events closely and use interventions to limit the severity of illness and reduce transmission.
• Post-exposure prophylaxis is an effective strategy to help protect those at highest risk, including individuals who are immunocompromised, pregnant women/pregnant individuals, those who are unimmunized, and young children.
• Several immunizing agents are available for use in Canada to protect individuals potentially exposed to measles, including measles-containing vaccines and human immunoglobulin blood products.
• The new NACI advice provides updated options for the use of measles-containing vaccines or immunoglobulin blood products when provinces and territories are responding to outbreaks.
• It also provides recommendations on how immunization can support measles outbreak responses, based on the complexity and scale of the outbreak, and includes strategies for protecting vulnerable groups, such as individuals who are immunocompromised, pregnant women/pregnant individuals, unimmunized populations, and young children exposed to measles. Additionally, guidance is provided on the optimal use of blood products in scenarios where vaccination history or blood tests can inform individual decision-making.
• NACI will continue to monitor the evidence and reassess guidance on measles pre- and post-exposure prophylaxis as the epidemiology of measles evolves globally and in Canada, updating recommendations as necessary.

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