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About COVID-19 vaccines

Many potential vaccines are being investigated in Canada and worldwide for use against COVID-19. Vaccines that have been authorized by Health Canada are safe, reliable and can help protect you, your family and our community from COVID-19. It is important that we all continue to follow public health measures and take everyday actions to stop the spread of the virus.

COVID-19 vaccination:

  • will work with your immune system to help protect you from COVID-19;
  • is a safe way to help build protection against the virus;
  • will help build community protection, stopping the spread of the virus in our community; and
  • is voluntary, but strongly encouraged.

COVID-19 vaccine safety

The Pfizer-BioNTech, Moderna, AstraZeneca and Janssen COVID-19 vaccines were authorized by Health Canada after thorough and independent reviews determined that they meet stringent safety, efficacy and quality requirements. Watch this short video for an overview of the vaccine development process (YouTube video). Learn more about how vaccines are developed and approved in Canada (external link).

Mixing Vaccine Types

Two doses of most COVID-19 vaccines are required for strong protection. Canada’s National Advisory Committee on Immunization (NACI) (external PDF) has updated its recommendations on using a different COVID-19 vaccine for a second dose. This is called vaccine interchangeability or “vaccine mixing.” Research shows that combining different COVID-19 vaccines will not lead to additional safety concerns or reduced effectiveness. Mixing similar vaccines to complete vaccine series is routinely done and has been previously approved for influenza, Hepatitis A, Hepatitis B, Measles, and Mumps vaccination. Learn more about the mixing of vaccines types (PDF file).

Receiving the same vaccine for the first and second dose, or a mixed schedule, are both safe options to gain strong protection from COVID-19. After any second dose, regardless of the vaccine (AstraZeneca, Moderna, or Pfizer), you may feel more, the same, or fewer side effects than after your first dose. To better understand the benefits and risks of interchanging COVID-19 vaccines, please talk to your health care provider who is familiar with your health history.

Which vaccine will I receive at a Halton clinic?

Halton Region vaccination clinics are currently offering Pfizer and Moderna vaccines. Starting Monday, June 14, the online booking system will now display which mRNA vaccine is being offered at each clinic. Residents will be able to book or reschedule their appointments (external link) and select either the Pfizer or Moderna vaccine at the time of booking, regardless of what type of vaccine was received during their first dose appointment.

Please note: While residents now have the option of selecting their vaccine type, Halton cannot guarantee which vaccine residents will receive at the clinic. Vaccine availability remains contingent on supply. All Halton residents will receive a Health Canada approved, age-appropriate vaccine.

If you received either Pfizer or Moderna vaccine for your first dose:

  • You may receive either Pfizer or Moderna vaccines as your second dose at a Halton Region vaccination clinic.
  • Pfizer and Moderna vaccines use a similar mRNA technology so the vaccines are interchangeable.
  • Pfizer vaccine is approved for those 12 years of age and older. Moderna vaccine is approved for those 18 years of age and older.
  • It is not recommended to receive AstraZeneca as your second dose.

If you received AstraZeneca vaccine for your first dose:

  • You may receive either AstraZeneca or an mRNA vaccine (Pfizer or Moderna) as your second dose.
    • To receive the AstraZeneca vaccine, contact the pharmacy or primary care provider where you got your first dose to book an appointment.
    • To receive an mRNA vaccine, residents can book a single second dose appointment at a Halton Region vaccination clinic. Appointments will be booked at a minimum of 12-weeks after your first dose and availability is contingent on vaccine supply. Residents can also book an mRNA vaccine directly with a participating pharmacy.
  • There is a possibility of increased temporary short-term side effects after receiving an mRNA vaccine as a second dose, including pain at the injection site, chills, headache, muscle and joint pain and fatigue.

Pfizer-BioNTech vaccine information

The Pfizer-BioNTech COVID-19 vaccine uses a method called messenger RNA (mRNA) technology. The mRNA in the vaccine tells the body’s cells to make "spike proteins," similar to what is found on the COVID-19 virus. The immune system responds to the spike proteins by making antibodies. These new antibodies will break down the spike proteins and get rid of them. The new antibodies will protect against COVID-19 infection in the future. The mRNA is broken down by the body shortly after injection and cannot affect the body’s DNA. mRNA vaccines are not live vaccines and cannot cause infection.

Two doses of the vaccine are required for full protection, given up to 16 weeks apart. It can be given to people 12 years of age and older, including seniors. At this time, there is no information on the long-term protection with this vaccine. In trials, the vaccine was 95% effective at preventing symptoms of the COVID-19 virus. Individuals may not be optimally protected until up to two weeks after their second dose of vaccine. It is essential to complete the vaccine series for best protection.

There is a small chance that you may still get COVID-19 after being vaccinated. It is important to continue to follow public health measures such as physical distancing, wearing a mask, and staying home if you are sick. Health care workers and other staff must still wear personal protective equipment (PPE) even after they have been vaccinated.

Some people may experience side effects from the vaccine, but they will likely be moderate and resolve after a few days. Some of the symptoms are part of the body’s response to developing immunity to a virus.

Common side effects that have been reported in clinical trials for this vaccine include:

very common ≥10%
(more than 1 in 10 doses)

  • pain at the injection site
  • headache
  • feeling tired
  • muscle or joint pain
  • fever or chills

common 1%-10%
(1 in 100 to 1 in 10 doses)

  • redness & swelling at the injection site

uncommon 1%
(1 in 100 doses)

  • enlarged lymph nodes

In rare cases, serious allergic reactions (anaphylaxis) can occur. Allergic reactions can be treated and are usually temporary. Seek medical attention if you have trouble breathing, have hives or swelling of the mouth and throat or a high fever (over 40 degrees C or 104 degrees F). Vaccine side effects will continue to be monitored as people receive the vaccine. If you get a reaction to the vaccine, contact your health care provider who will report the side effect directly to public health. Public health will keep track of the reported side effects to make sure the vaccine continues to be safe.

The Pfizer-BioNTech COVID-19 vaccine may be offered to individuals over the age of 12 who do not have contraindications.

Do not get the Pfizer-BioNTech vaccine if you:

It is strongly recommended that you speak with your treating health care provider if you have an autoimmune condition or immunodeficiency condition and are receiving any of the following treatments:

  • Have an autoimmune condition or immunodeficiency condition and are receiving any of the following treatments:
    • stem cell therapy
    • CAR-T therapy
    • chemotherapy
    • immune checkpoint inhibitors
    • monoclonal antibodies (e.g., rituximab) and other targeted agents (e.g., CD4/6 inhibitors, PARP inhibitors etc.)

You may choose to consult with your treating health care provider prior to vaccination if you:

  • have an autoimmune condition or immunodeficiency condition but are not receiving any of the above treatments
  • have a history of allergic reactions not related to the mRNA vaccine
  • are pregnant or breastfeeding

Moderna vaccine information

The Moderna COVID-19 vaccine uses a method called messenger RNA (mRNA) technology. The mRNA in the vaccine tells the body’s cells to make "spike proteins," similar to what is found on the COVID-19 virus. The immune system responds to the spike proteins by making antibodies. These new antibodies will break down the spike proteins and get rid of them. The new antibodies will protect against COVID-19 infection in the future. The mRNA is broken down by the body shortly after injection and cannot affect the body’s DNA. mRNA vaccines are not live vaccines and cannot cause infection.

Two doses of the vaccine are required for full protection, given up to 16 weeks apart. It can be given to people 18 years of age and older, including seniors. At this time, there is no information on the long-term protection with this vaccine. In trials, the vaccine was 95% effective at preventing symptoms of the COVID-19 virus..

There is a small chance that you may still get COVID-19 after being vaccinated. It is important to continue to follow public health measures such as physical distancing, wearing a mask, and staying home if you are sick. Health care workers and other staff must still wear personal protective equipment (PPE) even after they have been vaccinated.

Health Canada (external link) reported that side effects that followed administration of the Moderna vaccine were mild or moderate and are common of many vaccines, including:

  • pain at the site of injection
  • body chills
  • feeling tired
  • feeling feverish

Speak with your health care professional about any serious allergies or health conditions before receiving the Moderna COVID-19 vaccine.

Vaccine side effects will continue to be monitored as people receive the vaccine. If you get a reaction to the vaccine, contact your health care provider who will report the side effect directly to public health. Public health will keep track of the reported side effects to make sure the vaccine continues to be safe.

The Moderna COVID-19 vaccine may be offered to individuals over the age of 18 who do not have contraindications.

Do not get the Moderna vaccine if you:

It is strongly recommended that you speak with your treating health care provider if you have an autoimmune condition or immunodeficiency condition and are receiving any of the following treatments:

  • Have an autoimmune condition or immunodeficiency condition and are receiving any of the following treatments:
    • stem cell therapy
    • CAR-T therapy
    • chemotherapy
    • immune checkpoint inhibitors
    • monoclonal antibodies (e.g., rituximab) and other targeted agents (e.g., CD4/6 inhibitors, PARP inhibitors etc.)

You may choose to consult with your treating health care provider prior to vaccination if you:

  • have an autoimmune condition or immunodeficiency condition but are not receiving any of the above treatments.
  • have a history of allergic reactions not related to the mRNA vaccine
  • are pregnant or breastfeeding

AstraZeneca vaccine information

The AstraZeneca vaccine is a viral vector vaccine (external link). Unlike the Pfizer-BioNTech and Moderna vaccines which store the instructions to build spike proteins in RNA, the AstraZeneca vaccine uses DNA. The vaccine uses a harmless virus (called an adenovirus) as a delivery system. This is called a viral vector. Once the vaccine containing the viral vector enters the body, the vector virus produces the SARS-CoV-2 spike protein. Just like with the mRNA vaccines, the immune system responds to the spike proteins by making antibodies. These new antibodies will break down the spike proteins and get rid of them. The new antibodies will protect against COVID-19 infection in the future.

DNA is not as fragile as RNA. The viral vector (adenovirus) has a tough protein coat which protects the DNA inside. Therefore, the AstraZeneca vaccine does not need to be kept frozen.

Viral vector technology has been used for over ten years to produce many of the vaccines approved in Canada.

None of the COVID-19 vaccines currently approved by Health Canada use the live virus that causes COVID-19. You cannot get COVID-19 from a vaccine.

Two doses of the vaccine are required, given up to 16 weeks apart. After completing the two-doses, it may take another 14 days to achieve maximum protection against COVID-19. In trials, the vaccine was 81.6% effective at preventing symptoms of the COVID-19 virus. Data from the trials suggests that the vaccine is 100% effective against hospitalization from the COVID-19 disease (22 days after the first dose).

There is a small chance that you may still get COVID-19 after being vaccinated. It is important to continue to follow public health measures such as physical distancing, wearing a mask, and staying home if you are sick. Health care workers and other staff must still wear personal protective equipment (PPE) even after they have been vaccinated.

Common side effects following administration of the AstraZeneca vaccine are typically mild or moderate and are common of many vaccines (external link), including:

  • pain at the site of injection
  • body chills
  • feeling tired
  • feeling feverish

These are common side effects of vaccines and do not pose a risk to health. As with all vaccines, there’s a chance that there will be a serious side effect, but these are rare. A serious side effect might be something like an allergic reaction.

On May 11, the Province announced it would be pausing the rollout and administration of first doses of the AstraZeneca COVID-19 vaccine (external link). The decision was made out of an abundance of caution and due to the increasing reports of the rare blood clotting condition, known as vaccine-induced immune thrombotic thrombocytopenia (VITT), linked to the AstraZeneca vaccine.

Individuals should seek medical attention if they develop the following symptoms four or more days after receiving the AstraZeneca COVID-19 vaccine:

  • shortness of breath
  • chest pain
  • leg swelling
  • persistent abdominal (belly) pain
  • neurological symptoms (such as sudden onset of severe or persistent worsening headaches or blurred vision)
  • skin bruising or tiny blood spots under the skin beyond the site of the injection

If you experienced rare blood clots with unusual platelets following your first dose of the AstraZeneca COVID-19 vaccine, it is not recommended that you receive a second dose of any version of the AstraZeneca vaccine.

On May 21, 2021, the Province announced that second dose administration of the AstraZeneca COVID-19 vaccine will continue (external link). For a limited time during the week of May 24, individuals who received their first dose of AstraZeneca during the period of March 10, 2021 to March 19, 2021 may opt for an earlier dose interval of 10 weeks with informed consent. Halton Region Public Health did not offer the AstraZeneca vaccine during this time period. If you received the AstraZeneca vaccine during this time period outside of Halton, please contact the pharmacy or primary care office where you received your first dose to arrange your second dose appointment.

Individuals may choose to have a second dose of AstraZeneca COVID-19 vaccine, or wait to determine which vaccine they may receive at a later date when more data is available on mixed vaccine series (for example, having a first dose of AstraZeneca and a second dose of one of the mRNA vaccines). It is very important that people receive both doses to complete their vaccine series.

If individuals choose to receive AstraZeneca COVID-19 vaccine as their second dose, an interval of 12 weeks or more provides good protection. Individuals should be informed of the risks and benefits of their vaccine choices. The reported risk of VITT after the second dose of AstraZeneca COVID-19 vaccine is much lower than observed after the first dose.

For more information on the safety of the AstraZeneca vaccine, please read Health Canada’s website (external link).

The AstraZeneca COVID-19 vaccine has been approved by Health Canada for individuals over the age of 18 who do not have contraindications.

Do not get the AstraZeneca vaccine if you:

It is strongly recommended that you speak with your treating health care provider if you have an autoimmune condition or immunodeficiency condition and are receiving any of the following treatments:

  • Have an autoimmune condition or immunodeficiency condition and are receiving any of the following treatments:
    • stem cell therapy
    • CAR-T therapy
    • chemotherapy
    • immune checkpoint inhibitors
    • monoclonal antibodies (e.g., rituximab) and other targeted agents (e.g., CD4/6 inhibitors, PARP inhibitors etc.)

You may choose to consult with your treating health care provider prior to vaccination if you:

  • have an autoimmune condition or immunodeficiency condition but are not receiving any of the above treatments.
  • have a history of allergic reactions, or;
  • are pregnant or breastfeeding

Additional information will be posted as it is released from Health Canada.

Janssen vaccine information

The Janssen vaccine is a viral vector vaccine (external link). Unlike the Pfizer-BioNTech and Moderna vaccines which store the instructions to build spike proteins in RNA, the Janssen vaccine uses DNA. The vaccine uses a harmless virus (called an adenovirus) as a delivery system. This is called a viral vector. Once the vaccine containing the viral vector enters the body, the vector virus produces the SARS-CoV-2 spike protein. Just like with the mRNA vaccines, the immune system responds to the spike proteins by making antibodies. These new antibodies will break down the spike proteins and get rid of them. The new antibodies will protect against COVID-19 infection in the future.

DNA is not as fragile as RNA. The viral vector (adenovirus) has a tough protein coat which protects the DNA inside. Therefore, the Janssen vaccine does not need to be kept frozen.

Viral vector technology has been used for over ten years to produce many of the vaccines approved in Canada.

None of the COVID-19 vaccines currently approved by Health Canada use the live virus that causes COVID-19. You cannot get COVID-19 from a vaccine.

A single dose of the vaccine is required. It can be given to people over 18 years of age. In trials, the vaccine was 66% effective at preventing moderate to severe COVID-19.

There is a small chance that you may still get COVID-19 after being vaccinated. It is important to continue to follow public health measures such as physical distancing, wearing a mask, and staying home if you are sick. Health care workers and other staff must still wear personal protective equipment (PPE) even after they have been vaccinated.

Common side effects following administration of the Janssen vaccine are typically mild or moderate and are common of many vaccines, including:

  • pain at the site of injection
  • body chills
  • feeling tired
  • feeling feverish

These are common side effects of vaccines and do not pose a risk to health. As with all vaccines, there’s a chance that there will be a serious side effect, but these are rare. A serious side effect might be something like an allergic reaction.

Safety Concerns: Vaccine-Induced Thrombotic Thrombocytopenia (VITT)

Individuals should seek medical attention if they develop the following symptoms four or more days after receiving the Janssen (COVISHIELD) COVID-19 vaccine:

  • shortness of breath
  • chest pain
  • leg swelling
  • persistent abdominal (belly) pain
  • neurological symptoms (such as sudden onset of severe or persistent worsening headaches or blurred vision)
  • skin bruising or tiny blood spots under the skin beyond the site of the injection

For more information on the safety of the Janssen (COVISHIELD) vaccine, please read Health Canada’s website (external link).

The Janssen COVID-19 vaccine is approved for use in people 18 years of age and over.

Additional information will be posted as it is released from Health Canada.

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