The AstraZeneca vaccine, like all vaccines, may cause side effects in some people. Symptoms are usually mild and resolve after a few days. Some of the symptoms are part of the body’s response to developing immunity to a virus.
The most commonly reported side effects are:
- pain at the injection site
- swelling, and colour changes in the skin (for example. red, purple) at the injection site
- muscle or joint pain
- mild fever.
Ongoing studies on the COVID-19 vaccines have found that serious side effects are extremely rare.
Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT)
Very rarely, the AstraZeneca vaccine has been linked to a rare form of blood clot after vaccination.
Experts are calling this Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT). These blood clots:
- typically occur 4 to 28 days after vaccination;
- are associated with low platelets (tiny blood cells that help form blood clots to stop bleeding); and
- seem to be rare.
It is thought that the vaccine causes an immune reaction that produces antibodies which activates platelets, cells in our blood that form blood clots.
VITT can usually be treated. Individuals should seek immediate medical attention if they develop any of these symptoms after being vaccinated with the AstraZeneca:
- shortness of breath
- chest pain
- leg swelling or pain
- persistent abdominal (belly) pain
- skin bruising (other than at site of vaccination)
- red or purple spots or blood blisters under the skin
- sudden onset of severe or persistent worsening headaches
- blurred vision
- double vision
- confusion or seizures
- difficulty speaking or moving part of the body
Individuals who experienced rare blood clots with unusual platelets following their first dose of the AstraZeneca COVID-19 vaccine should not receive a second dose of any version of the AstraZeneca vaccine.
Capillary leak syndrome
Very rare cases of capillary leak syndrome, a condition that causes fluid leakage from small blood vessels (capillaries), have been reported after vaccination with AstraZeneca vaccine. Symptoms are often linked with feeling faint (due to low blood pressure). People with a history of capillary leak syndrome should not receive the AstraZeneca/COVISHIELD COVID-19 vaccine.
Individuals should be informed of the risks and benefits of their vaccine choices.
For more information on the safety of the AstraZeneca vaccine, please read Health Canada’s website (external link).