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Are COVID-19 vaccines effective?

Beginning about two weeks after the first dose, all COVID-19 vaccines currently approved are very effective at preventing COVID-19 infection and serious illness.

When a large percentage of the population becomes immune to COVID-19, the spread of the virus will slow down or stop. Vaccination is our best shot for allowing individuals, families and workers to safely resume normal life.

How well is the vaccine tested? Is it safe?

Only vaccines that are safe and effective for widespread use are approved by Health Canada for use in Canada. Vaccines are tightly regulated and closely monitored in Canada and each vaccine has been rigorously tested in a series of large-scale trials. COVID-19 vaccines were tested with 70,000 people and millions more have already received them.

While mild or moderate side effects are possible, they typically subside in a few days. These might include soreness at the injection site, body chills, feeling tired or feverish. Some symptoms can be part of the body’s response to developing immunity. Side effects may be more common with the second dose. Serious side effects are rare.

Some side effects can be similar to symptoms of COVID-19. If you have concerns about symptoms after immunization, please speak to your health care provider to determine if you need further assessment.

Vaccines are continually monitored for safety and effectiveness at federal, provincial and local levels. Health care providers and the public also play a part in this, by reporting any uncommon side effects after a receiving a vaccine.

How can the vaccine be developed so quickly?

COVID-19 vaccines were developed faster than some other vaccines because of never-before seen levels of collaboration and funding invested around the world. Health Canada only approves vaccines that are safe and effective and meet all standards.

Development of the COVID-19 vaccine is progressing quickly for many reasons, including:

  • Leveraging existing vaccine research programs
  • International collaboration among scientists, health professionals, researchers, industries and governments
  • Increased dedicated funding
  • Quick recruitment of participants for clinical trials
  • Rapid set-up and analysis of clinical trials to demonstrate vaccine effectiveness
  • Reduction of unnecessary time delays in the vaccine approval process

Is mRNA technology new?

Like all vaccines, COVID-19 mRNA vaccines have been rigorously tested for safety before being approved. mRNA technology has been studied for more than a decade. The “m” from mRNA means “messenger” which is exactly what the vaccine does – it sends a message to your cells to make antibodies to fight against the virus that causes COVID-19. It blocks the virus from attaching and getting into your body’s cells. It cannot change your DNA and it cannot not give you COVID-19.

Will the vaccine still work on new COVID-19 emerging strains? Are the new strains more contagious?

Both Pfizer and Moderna are testing their vaccines to see if they work against new strains of the virus.  Early evidence suggests vaccines will be effective against the B.1.1.7 variant. More information on this will be provided as it becomes available.

We are still learning about the new COVID-19 strains; however, early information suggests these variants are more contagious. This is why it is important we remain vigilant in our efforts to reduce spread and continue to follow all public health measures.

Can I choose which vaccine I get? Are some better than others?

All vaccines approved by Health Canada are very effective at preventing COVID-19 infection, serious illness, hospitalization and death. There is no need to delay or wait for one vaccine over another.

Vaccine clinics in York Region will have different vaccines on hand at different times. Which vaccines administered at a clinic is currently based on the availability of the vaccine supply, as directed by the Federal and Provincial governments.

All COVID-19 vaccines provide sustained, substantial protection approximately 14 days following the first dose. Residents are not provided a choice between vaccine when visiting a clinic.

It is important to get vaccinated as soon as the vaccine is offered to you, as it ensures we can move to vaccinate everyone as safely and quickly as possible, based on priority order.


COVID-19 Vaccinations in York Region


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