Health & Wellness

Guidance on AstraZeneca Vaccine Changes Again

The COVID-19 vaccine will no longer to be given to Canadians under 55—for now

By Caitlin Finlay


For the second time in less than a week, the official recommendation regarding the Oxford-AstraZeneca vaccine has changed, and distribution of the vaccine to Canadians under the age of 55 has been put on hold.

In late February, the AstraZeneca-Oxford vaccine became the third COVID-19 vaccine to be approved for use in Canada. (Health Canada approved the Pfizer-BioNTech and Moderna vaccines in December 2020, and the Janssen (Johnson & Johnson) vaccine on March 5.) On March 24, Health Canada reiterated that the AstraZeneca shot is safe and effective but added a warning to the vaccine’s label about “very rare reports of blood clots associated with low levels of blood platelets.” On Monday, March 29, the National Advisory Committee on Immunization (NACI) issued a recommendation that the vaccine not be used in adults under 55 while Health Canada continues to investigate cases of serious blood clots following vaccination.

Concerns over the vaccine’s safety were raised in Europe when rare cases of blood clots were reported in people who had received it—mostly women under 55—and several European countries suspended the use of the AstraZeneca vaccine as a preventive measure. Following these reports, Health Canada collaborated with the European Medicines Agency (EMA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA) to investigate. On March 18, Health Canada, the EMA, and the MHRA released statements declaring the vaccine safe and effective with no overall risk of blood clots.

Since then, however, new information suggests that the incidence of blood clots is higher than had been thought. While original estimates were approximately one case of the adverse reaction per 1,000,000 people vaccinated with the AstraZeneca vaccine, estimates from the Paul-Ehrlich Institut in Germany suggest a higher rate of one per 100,000.

Photo: iStock/Manjurul.