Canada’s National Advisory Committee on Immunization (NACI) is recommending a pause in the use of AstraZeneca’s COVID-19 vaccine in people under 55 following reports from Europe of 18 younger patients, mostly women, developing blood clots usually within 14 days following its use. The measure is considered precautionary, as over 300,000 doses of the vaccine have been administered in Canada without any reports of that reaction. The vaccine remains recommended for use in people 55 years and older.