Event Details

PHO Grand Rounds: Measles and varicella maternal antibody waning in Ontario infants

Infants are at risk for severe complications from infectious diseases, including measles and varicella. In Ontario, where measles has been eliminated for two decades, maternal immunity is mainly from vaccination rather than natural infection and immunity is not boosted due to lack of exposure to measles. Infant immunity may therefore wane below the protective threshold sooner than anticipated, leaving a wide susceptibility gap before infants are immunized at 12 months. Since not all mothers are immune from varicella and the introduction of varicella vaccine has changed disease epidemiology, infants may also be susceptible to varicella with a wide susceptibility gap until vaccination at 15 months.

In this presentation, we will outline the epidemiology of measles and varicella. We will also describe a study performed at the Hospital for Sick Children in Toronto to investigate immunity to measles and varicella in infants that are less than 12 months of age. We will discuss the implications of the findings to public health management of cases and exposures.

By the end of this session, participants will be able to:

  1. Describe the epidemiology of measles and varicella in Ontario
  2. Describe waning of maternal antibodies to measles and varicella in Ontario infants
  3. Discuss the implications of these findings on future measles and varicella control

Presenter(s): Michelle Science and Shelly Bolotin

Michelle Science is an Infectious Disease Physician at The Hospital for Sick Children and an Assistant Professor at the University of Toronto. She is the Medical Advisor for Infection Prevention and Control (IPAC) and the Medical Lead of the Antimicrobial Stewardship Program at The Hospital for Sick Children. More recently, she joined Public Health Ontario as a consulting IPAC Physician. Her research is focused in the areas of preventing healthcare-associated infections and optimizing the use of antimicrobials, particularly in vulnerable populations such as infants. 

Shelly Bolotin is a Scientist in Communicable Diseases, Emergency Preparedness and Response at Public Health Ontario and an Assistant Professor at the Dalla Lana School of Public Health and the Department of Laboratory Medicine at the University of Toronto. Her research program focuses on measuring population immunity to vaccine-preventable diseases. 



The opinions expressed by speakers and moderators do not necessarily reflect the official policies or views of Public Health Ontario, nor does the mention of trade names, commercial practices, or organizations imply endorsement by Public Health Ontario.


PHO Rounds are a self-approved group learning activity (Section 1) as defined by the Maintenance of Certification Program of the Royal College of Physicians and Surgeons of Canada (RCPSC). In order to receive written documentation for Continuing Medical Education (CME) credits, please check “Yes” beside the question “Do you require CME credits?” on the registration form.

College of Family Physicians of Canada (CFPC) Affiliate Members may count RCPSC credits toward their Mainpro+ credit requirements. All other CFPC members may claim up to 50 Certified credits per cycle for participation in RCPSC MOC Section 1 accredited activities.

PHO Grand Rounds are also approved by the Council of Professional Experience for professional development hours (PDHs) for members of the Canadian Institute of Public Health Inspectors (CIPHI).

For more information or for a record of registration for other Continuing Education purposes, please contact events@oahpp.ca


Public Health Ontario is committed to complying with the Accessibility for Ontarians with Disabilities Act (AODA). If you require accommodations to participate in this event, please contact 647-260-7100 or events@oahpp.ca.

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Published 5 Dec 2019