Skip to main content Skip to Navigation Skip to Footer

AstraZeneca Vaccine

Common questions and answers to pausing the administration of the AstraZeneca vaccine

Why is the Ontario government pausing the use of AstraZeneca?

As of May 11th, 2021, Ontario has paused the rollout and administration of first doses of the AstraZeneca COVID-19 vaccine/COVISHIELD vaccine. This decision was made out of an abundance of caution due to an observed increase in the rare blood clotting condition, known as vaccine-induced immune thrombotic thrombocytopenia (VITT). Over last few days, there have been increased reports of VITT (1.7 per 100,000, up from 0.9 per 100,000 doses administered).

The decision to pause is also based on the increased and reliable supply of the Pfizer and Moderna mRNA vaccines and the downward trend in cases.

Public Health Ontario, the Science Advisory Table and federal, provincial, and territorial partners, are reviewing the data to consider options for the use of the AstraZeneca vaccine moving forward.

I already received my first dose of AstraZeneca, what about my second dose?

Ontario is pausing the rollout and administration of first doses of the AstraZeneca vaccine at this time.

Data from the UK points to a much-reduced risk of vaccine-induced immune thrombotic thrombocytopenia (VITT) in second doses of AstraZeneca.

Based on the much higher risks of COVID-19 infection recently observed in Ontario including hospitalization, serious illness and death, we maintain that those who received their first dose with the AstraZeneca vaccine did absolutely the right thing to prevent illness, and to protect their communities.

A second dose of a COVID-19 vaccine is needed for the best protection against COVID-19. Being fully vaccinated is especially important because it provides much better protection against the delta variant of concern (VOC) that is now in the region.

Those who have received a first dose of AstraZeneca/COVISHIELD COVID-19 vaccine have a choice about the type of vaccine for the second dose:

  • Receive the AstraZeneca/COVISHIELD COVID-19 vaccine for the second dose no less than 8 weeks following the first dose, or
  • Receive an mRNA COVID-19 vaccine (Pfizer-BioNTech or Moderna) for the second dose no less than 8 weeks following the first dose. 

The National Advisory Committee on Immunization (NACI) updated their recommendations on June 17, 2021 for individuals who received a first dose of AstraZeneca/COVISHIELD. An mRNA vaccine is now preferred for second doses because current evidence suggests this may produce a better immune response and there is good safety data about having an mRNA vaccine for a second dose. 

Individuals who receive two doses of the AstraZeneca/COVISHIELD vaccine are considered protected and do not require additional doses. Two doses of AstraZeneca/ COVISHIELD COVID-19 vaccine provide good protection against symptomatic COVID-19 and severe outcomes, like hospitalizations and death. 

I already received the AstraZeneca vaccine, should I be worried?

Individuals who received the AstraZeneca COVID-19 vaccine were asked to monitor for the following symptoms for 20 days after receiving the vaccine: shortness of breath, chest pain, leg swelling, persistent abdominal pain, neurological symptoms including sudden onset of severe or persistent worsening headaches or blurred vision, skin bruising (other than at the site of vaccination) or petechiae. You are unlikely to experience any side effects related to AstraZeneca if it has been more than 20 days since you received the vaccine.

Based on the much higher risks of COVID-19 infection recently observed in Ontario including hospitalization, serious illness and death, we maintain that those who received their first dose with the AstraZeneca vaccine did absolutely the right thing to prevent illness, and to protect their communities.

Why did the government approve AstraZeneca if it isn’t safe?

Health Canada has completed a rigorous scientific review of the available medical evidence to assess the safety of the AstraZeneca COVID-19 Vaccine. As with all vaccines, there was continued monitoring for the safety and efficacy of the AstraZeneca COVID-19 vaccine after authorization.

This decision was made out of an abundance of caution due to an observed increase in the rare blood clotting condition, known as vaccine-induced immune thrombotic thrombocytopenia (VITT). Over last few days, there have been increased reports of VITT (1.7 per 100,000, up from 0.9 per 100,000 doses administered).

Public Health Ontario, the Science Advisory Table and federal, provincial, and territorial partners, are reviewing the data to consider options for the use of the AstraZeneca vaccine moving forward.