COVID-19 Vaccine Frequently Asked Questions
Below you will find answers to frequently asked questions about COVID-19 vaccines. This list will be updated as information becomes available and as additional vaccines are approved by Health Canada.
About the vaccines
How do COVID-19 vaccines work?
Vaccines teach your immune system how to protect you from diseases. It's much safer for your immune system to learn this through vaccination than by catching the diseases and attempting to treat them.
mRNA technology has been studied for more than 10 years, most often in cancer research and treatment as well as in the development of new vaccines against such infections as pandemic influenza and rabies. Shortly after COVID-19 was identified scientists were able to map the genes that make up the COVID-19 virus. Once the structure of the genes was known, especially of the spike protein that allows that virus to fuse with and enter our cells, scientists were able to quickly create the vaccine and start the clinical trials that have resulted in the Pfizer and Moderna vaccines that have been approved for use by Health Canada.
Below is an explanation of how the approved Pfizer-BioNtech and Moderna mRNA COVID-19 vaccines work with your body’s immune response to fight off the COVID-19 virus.
COVID-19 mRNA vaccines tell your body to make "spike proteins" (these cover the outside of the virus and allow it to attach to and enter our cells) specific to virus that causes COVID-19.
- COVID-19 mRNA vaccines tell your body to make "spike proteins" (these cover the outside of the virus and allow it to attach to and enter our cells) specific to virus that causes COVID-19.
- Your immune system responds to spike proteins by making antibodies that bind to and block the spike protein on the virus’s surface. This is important for protection from disease because the spike protein is what attaches to human cells, allowing the virus to enter. Blocking this entrance prevents infection.
- Your new antibodies will attack the spike proteins
- Your new antibodies and immune cells will protect you from illness if you are exposed to COVID-19 virus in the future by remembering how to attack the spike protein
Health Canada approved the AstraZeneca COVID-19 vaccine on February 26, 2021 and approved the Janssen/Johnson & Johnson COVID-19 vaccine on March 5, 2021. These vaccines are not mRNA vaccines, they are a different type of vaccine called viral vector vaccines.
- The COVID-19 virus is studded with proteins that it uses to enter human cells, the so-called spike protein.
- The AstraZeneca and Janssen/Johnson & Johnson viral vector COVID-19 vaccines use a weakened cold virus to carry the instructions for our body to make COVID-19 "spike proteins.” The cold virus has been modified so you will not get a cold from it. Our body will make antibodies against the spike protein to protect us from illness if we are exposed to COVID-19 in the future.
- One benefit of using a viral vector to carry the spike protein into the body is that these vaccines are more stable and do not have to stay frozen. The vaccines are expected to last for at least six months when refrigerated at 2–8°C. This may mean easier distribution of the viral vector vaccines as supply increases.
Will the vaccines interact with your DNA in any way?
mRNA is a short-form of ‘messenger RNA’ – meaning that it’s a messenger.
DNA is contained in the nucleus of our cells and mRNA cannot get into the nucleus or interact with our DNA.
mRNA cannot change your DNA, it is a part of our genetic material that gives instructions to the body, like a recipe. It simply delivers a message.
- For COVID-19, the mRNA vaccine tells the body to make a harmless “spike protein”. This spike protein is found on the outside of the COVID-19 virus (but is not the virus itself). Our immune system recognizes the spike protein as something that shouldn’t be there and quickly works to attack it by building antibodies and immune cells that will attack the COVID virus if you are exposed in the future.
Human cells break down and get rid of the mRNA soon after they have finished using the instructions. mRNA does not interact with the part of our cells that holds our DNA and cannot be ‘swapped out’ or change the DNA sequence (there only function is to deliver the message of the spike protein to the cell).
The AstraZeneca and Janssen/J&J COVID-19 vaccines are delivered differently (see above on how it works). They contain the COVID-19 spike protein DNA gene which gets read by the cell and translated into the mRNA to replicate the spike protein (not the virus, just the protein). The mRNA and your DNA do not interact.
Can I get other vaccines at the same time or after my COVID-19 vaccine?
COVID-19 vaccines should not be given at the same time as other vaccines:
- If possible, wait for at least 14 days after receiving another vaccine before getting the mRNA COVID-19 vaccine. It is not a safety concern if it has been less than 14 days. Separating vaccines by 14 days can help us determine which vaccine may have caused a side effect if one happens.
- Wait at least 28 days after finishing the two-dose vaccine series of a mRNA COVID-19 vaccine before getting another vaccine (except in the case where another vaccine is required because you have been exposed to another vaccine-preventable disease).
Please talk to your immunization provider if you have more questions.
Will I have to get more than one dose of the COVID-19 vaccine?
Building up immunity takes time. One dose of vaccine may not be enough to provide individual protection. You may need to get a second shot to allow your body to develop adequate immunity.
For the currently approved Pfizer-BioNtech COVID-19 vaccine, two doses of the vaccine are required for better protection, given 21 days apart. It can be given to people 16 years of age and older, including seniors. After completing the two-doses, it may take another seven days to achieve maximum protection against COVID-19. The Pfizer-BioNtech clinical studies included over 43,000 participants and was 95% effective in preventing COVID-19 beginning 2 weeks after the second dose.
Two doses are also required for the Moderna vaccine. Based on studies in about 30,000 participants, the Moderna COVID-19 vaccine was 94.1% effective in preventing COVID-19 beginning 2 weeks after the second dose. This means that people may not be fully protected against COVID-19 until at least 14 days after the second dose. The Moderna vaccine is approved for people 18 years or older at this time.
The AstraZeneca COVID-19 vaccine also requires two doses, 4 to 12 weeks apart.
Based on clinical trials, the vaccine was 62% effective in preventing COVID-19 beginning 2 weeks after the second dose. This effectiveness rate is based on an analysis of results from trial participants who had received the 2-dose regimen that will be used in Canada. The AstraZeneca vaccine is approved for people 18 years or older at this time but is not recommended by the National Advisory Committee on Immunization in Canada for adults over 65 given limited evidence with this population (source: https://www.canada.ca/en/public-health/services/immunization/national-advisory-committee-on-immunization-naci/recommendations-use-covid-19-vaccines.html).
The Janssen/J&J COVID-19 vaccine requires one dose – it is the only single dose vaccine currently approved in Canada. Based on studies in about 43,000 participants, the Janssen COVID-19 vaccine was 66% effective in preventing symptomatic COVID-19 disease beginning 2 weeks after vaccination. Immunity develops over time. You won’t develop significant protection against COVID-19 for at least 2 weeks. The Janssen vaccine is approved for use in people 18 and older.
If I get the vaccine will I be immune to COVID-19 for my entire lifetime?
At this time, the duration of protection from the vaccines remains unknown, and further doses may be necessary. The duration of immunity from contracting the infection also remains unknown. Ongoing monitoring of the COVID-19 vaccines and their effects on long-term immunity continues.
Will I still have to follow other COVID-19 measures once I get the vaccine?
Yes, it is essential that you still act to prevent the spread of COVID-19 in the community, so it is important to follow public health measures until we have reached a level of community vaccination that suggests widespread immunity. This includes wearing a mask when indoors, or when you cannot physically distance from others, continuing to avoid crowded spaces and social gatherings, regular handwashing, and staying home when sick.
Will these COVID-19 vaccines work on new strains of the disease?
Data about the efficacy of authorized vaccines against variants is evolving. The National Advisory Committee on Immunization in Canada will continue to monitor the evidence and update recommendations as needed. However, data from the U.K arm of the phase II/III trials of the AstraZeneca COVID-19 vaccine indicated that it was effective against mild to moderate cases from the U.K. variant (B.1.1.7). Vaccine efficacy was 74.9% after two doses against symptomatic infection from the B.1.1.7 (source: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3779160).
Making a decision about getting vaccinated
I’ve already had COVID-19/have COVID-19 antibodies. Do I need the vaccine?
Yes. You should still get vaccinated. At this time, we do not know the length of immune response in those who’ve had the COVID-19 infection. . When you have the COVID-19 vaccine, it can help protect you against re-infection and may, we hope, also prevent you from transmitting the virus to others.
If there are effective treatments for COVID-19, why do we need a vaccine?
It is always better to prevent an illness, rather than get it and treat it. A vaccine can help stop you getting ill, lessen the impact of COVID-19 and slow it spreading in the community. There is some evidence to show that even a mild case of COVID-19 can be harmful to a person’s respiratory and cardiac system.
How do I decide if this is right for me and my family?
Get informed and make your decisions based on evidence and what makes sense for your family. Note that the Pfizer-BioNtech COVID-19 vaccine is currently only approved for people over 16 years of age. The Moderna vaccine is approved for people who are 18 years of age and older.
The AstraZeneca COVID-19 vaccine is currently approved by Health Canada for use in adults 55 and over. Read more about the AstraZeneca vaccine suggested use guidance: NACI rapid response: Recommended use of AstraZeneca COVID-19 vaccine in younger adults
The Janssen/J&J COVID-19 vaccine is currently approved by Health Canada for adults 18 and over.
Vaccination is a personal choice that the vast majority of Canadians agree is part of good health and important for prevention of serious disease.
Public Health recommends that everyone who is eligible gets the vaccine once it is available, but recognize that the choice is not always as easy as following this advice. Take the time to read and understand the vaccine information on this page and from other reliable sources.
Follow-up by asking questions and reaching out to trusted medical experts like your family doctor, nurse practitioner, or health care provider.
How many people have been vaccinated in Hamilton?
Check the vaccine distribution page to find out how many people have been vaccinated in Hamilton
Getting the vaccine
Safety and effectiveness of the COVID-19 vaccine
To date, there are 4 COVID-19 vaccines approved for use in Canada by Health Canada.
- Pfizer-BioNTech - approved December 9, 2020
- Moderna – approved December 23, 2020
- AstraZeneca – approved February 26, 2021
- Janssen/Johnson & Johnson – approved March 5, 2021
Other vaccines are currently at various stages of regulatory approval by Health Canada.
Vaccine development and approval
Development and approval of the vaccine feels rushed. Can we trust that the COVID vaccine is safe?
There is a misconception that vaccine research must take a long time. While creating a new vaccine can sometimes take years, the progress on COVID-19 vaccines is happening quickly for many reasons, including:
- advances in science and technology
- international collaboration among scientists, health professionals, researchers, industry and governments
- increased dedicated funding
For any vaccine to reach the general public it must pass careful evaluation by Health Canada and will have to pass safety standards. What made this vaccine approval feel rushed in comparison to other vaccines is the result of a highly focused and shared effort by researchers and scientists in every part of the world - combined new processes for review and evaluation of clinical trial data in addition to increased funding for vaccine research.
No corners were cut while creating the vaccines. One minor change to the usual process was put in place: clinical trials were run at the same time as the vaccines were being made/manufactured; that way, vaccines could be shipped out to different countries as soon as the vaccines were approved by the different countries’ health authorities.
Who participated in the clinical trials?
The different clinical trials included over 70,000 people. 43,448 people were included in the Pfizer trials; 30,000 people were included in the Moderna vaccine trials.
Between 35-40% of the participants were Black or African American, Latinx and Hispanic in both vaccine clinical trials (Pfizer BioNtech and Moderna).
Source: Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine. Polack et al. The New England Journal of Medicine
23,848 people participated in the clinical trials for AstraZeneca. Approximately 10% of participants in the clinical trials for AstraZeneca identified as Black.
43, 783 people from across the United States, Latin America, and South Africa participated in the clinical trials for the Janssen/J&J vaccine. Clinical trials for the Janssen/J&J vaccine included participants from across multiple age ranges and racial groups. Source: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/janssen.html
Clinical trials make efforts to include a wide range of people to make sure that the evidence would support a wide range of people benefitting from vaccination. There are some groups that were not included in the clinical trials, including people who are pregnant or breastfeeding, people under the age of 16, or people who have weaker immune systems. Often vaccine clinical trials start with healthier people and, if successful, go on to other at-risk populations, for example, people with chronic illnesses. This can take additional time to decide if a vaccine is effective but is very important as these people are at greater risk of adverse COVID-19 impacts.
Clinical trials in children older than 12 years old have begun. Canadian guidelines for COVID-19 vaccines in people who are pregnant, breastfeeding or are immunocompromised can be found here.
The vaccine trials included people over the age of 65 and the vaccine was found to be safe and effective in this age group.
Did the vaccine trials include Black, Indigenous, or Latinx people?
Yes. Clinical trials included over 70,000 volunteers. Between 35-40% of the participants were Black or African American, Latinx and Hispanic in both vaccine clinical trials (Pfizer BioNtech and Moderna).
Several hundred people in the trials self-identified as American Indians or Alaska Natives, but this number was too small to be certain how effective the vaccine was in preventing COVID infections in Indigenous people.
Approximately 10% of participants in the clinical trials for AstraZeneca identified as Black.
Clinical trials for the Janssen/J&J vaccine included the following breakdown of participants: 45.3% Hispanic or Latino, 19.4% Black or African American, 9.5% American Indian or Alaska Native, and 3.3% Asian. 33.5% were aged 60 years and older. Source: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/janssen.html
What are the efficacy rates for vaccines against severe disease and hospitalization?
All of the approved vaccines have a high efficacy rate against severe disease. In the clinical trials, efficacy against severe disease was shown to be:
- Pfizer: 75-100% (after dose 2)
- Moderna: 100% (14 days after dose 2)
- AstraZeneca: 100% (after dose 2)
- Janssen: 85.4% (28 days after dose)
Vaccine efficacy is the percentage reduction in disease incidence in a vaccinated group compared to an unvaccinated group under ideal (i.e., clinical trial) conditions (source: WHO). A vaccine with an efficacy of 90% in a trial, for instance, means there was a 90% reduction in cases of disease in the vaccinated group compared to the unvaccinated (or placebo) group.
What is in the COVID-19 vaccine?
None of the approved COVID-19 vaccines in Canada contain egg.
The ingredients in the Pfizer BioNtech COVID-19 vaccine authorized for use in Canada are:
- Medicinal ingredient
- Non-medicinal ingredients
- ALC-0315 = ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate)
- ALC-0159 = 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide
- dibasic sodium phosphate dihydrate
- monobasic potassium phosphate
- potassium chloride
- sodium chloride
- water for injection
The ingredients in the Moderna COVID-19 vaccine authorized for use in Canada are:
- Medicinal ingredient
- Non-medicinal ingredients
- 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)
- acetic acid
- lipid SM-102
- polyethylene glycol (PEG) 2000 DMG
- sodium acetate
- tromethamine hydrochloride
- water for injection
Note: Polyethylene glycol (PEG) is in both mRNA vaccines. It can also be found in laxatives, makeup, skin care products, personal lubricants, toothpastes, and some contact lenses. It is also in cough syrup, and in some food and drinks.
Pfizer/BioNTech and Moderna have reported that their vaccines contain no preservatives.
The ingredients in the AstraZeneca COVID-19 vaccine authorized for use in Canada are:
- Medicinal ingredient
- Adenovirus vector vaccine
- Non-medicinal ingredients
- disodium edetate dihydrate (EDTA)
- L-histidine hydrochloride monohydrate
- magnesium chloride hexahydrate
- polysorbate 80
- sodium chloride
- water for injection
The ingredients in the Janssen/J&J COVID-19 vaccine authorized for use in Canada are:
- Medicinal ingredient
- adenovirus vector vaccine
- Non-medicinal ingredients
- 2-hydroxypropyl-β-cyclodextrin (HBCD)
- citric acid monohydrate
- hydrochloric acid
- sodium chloride
- sodium hydroxide
- trisodium citrate dehydrate
- water for injection
Different vaccines have different storage needs. For example, the Pfizer/BioNTech vaccine must be stored at minus 70 degrees Celsius, and the Moderna vaccine needs to be stored at minus 20 degrees Celsius. Both of these vaccines use messenger RNA, or mRNA, to teach your cells how to make a protein that will cause an immune response to COVID-19. However, messenger RNA is fragile and can break down easily. Storing messenger RNA vaccines in an ultracold environment keeps them stable and safe. You should not worry about these temperatures. Vaccines are thawed before injection.
The AstraZeneca and Janseen/J&J vaccines are stored at 2-8 degrees Celsius making it more stable to transport.
Do COVID-19 vaccines contain animal by-products
The mRNA COVID-19 vaccines have been deemed ‘permissible or recommended’ by the Vegan Society, Muslim and Jewish councils in the USA. There are no pork-derived materials, the fatty layers that protect the mRNA are plant-based or synthetic, there are no blood fractions or fetal cells products in the vaccines.
Source: South Asian COVID Task Force Canada.
The AstraZeneca and Janssen/J&J vaccines do not contain any animal by-products. AstraZeneca and Janssen/J&J use fetal cell lines that have been in use for producing certain vaccines since 1973 and 1985 to manufacture the vaccines. Other vaccines that use these cell lines include hepatitis A, rubella, chickenpox and rabies.
Does the vaccine contain a microchip and have the ability to track or gather personal information into a database?
No, the vaccine does not contain a “microchip”. This concern started after comments made by Bill Gates from The Gates Foundation about a digital certificate of vaccine records. A digital certificate is not something that can be contained within a vaccine and is not a microchip. The technology referred to by Gates has nothing to do with the development, testing or distribution of the COVID-19 vaccine.
Vaccine side effects
What are the potential side effects of the vaccine?
After being vaccinated, it's common to have mild side effects. This is the body's natural response, as it's working hard to build immunity against the disease. This is known as the inflammatory response or reaction. Side effects will likely be moderate and resolve after a few days.
Common side effects that have been reported in the clinical trials for the Pfizer BioNtech COVID-19 vaccine include:
|very common ≥10%
(more than 1 in 10 doses)
(1 in 100 to 1 in 10 doses)
(1 in 100 doses)
These effects are more likely after the second dose of vaccine and will typically go away in a day or two. These effects are a normal part of your body’s response to most vaccines – it is a sign that your body’s immune system is learning how to recognize and fight the virus that causes COVID-19. Some people may experience more serious allergic reactions to the vaccine, but these are unlikely and tracked closely by Health Canada as part of on-going monitoring of vaccine safety.
If you have questions about these effects, reach out to a trusted health care provider, like your family doctor, nurse or local pharmacist.
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 face and throat. 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.
- Delay getting vaccinated if you have a fever, are sick with COVID-19 symptoms, or have received a vaccine in the past 14 days.
- Avoid trying to get pregnant for at least two months after getting both doses of the vaccine.
- Consult your health care provider if you have a bleeding disorder or are on blood thinner medication.
Visit Health Canada for more information on the side effects of the Pfizer BioNTech COVID-19.
Common side effects that have been reported in the clinical trials for the Moderna COVID-19 vaccine include mild to moderate: pain at the site of injection, body chills, feeling tired and feeling feverish.
Visit Health Canada for more information on the potential side effects of the Moderna COVID-19 vaccine.
Common side effects of the AstraZeneca vaccine include pain at the site of injection, body chills, feeling tired and feeling feverish. Visit Health Canada for more information on the potential side effects of the AstraZeneca COVID-19 vaccine.
Common side effects of the Janssen/J&J vaccine include pain at the site of injection, body chills, feeling tired and feeling feverish. Visit Health Canada for more information on the potential side effects of the Janssen/J&J COVID-19 vaccine.
Have COVID-19 vaccines been linked to infertility or miscarriage?
There is no science-based reason why a COVID-19 vaccine would lead to infertility or miscarriage.
The best evidence comes from women who got sick with COVID-19 while pregnant. Studies show that pregnant women are more likely to be hospitalized when they have COVID-19, but they are not more likely to miscarry.
If you were to get COVID-19, your body creates the same immune response as it does when you receive the vaccine. If this immune response caused miscarriages, we would have already seen more miscarriages in women naturally infected with COVID-19. This has not happened.
Could the vaccine side effects be worse than getting COVID-19?
Some people’s experience of COVID-19 may be mild, but it can also cause some people to become very sick or even lead to death. There is some research to show that even a mild case of COVID-19 can be harmful to a person’s lungs (which makes breathing hard) and to their heart and cardiovascular system (your heart and how blood flows through your body). There is also a worrisome number of people experiencing on-going and at times debilitating symptoms for weeks or months after their initial COVID-19 infection (sometimes called ‘long COVID’).
On social media, some people are saying that only 1%-2% of people with COVID-19 die from it and that people should not be vaccinated because the chance of dying is low. However, even if only 1% of people with COVID-19 die, that is 10 times more than the seasonal flu. Your risk of dying from COVID-19 also increases as you age, is you are male or if you have chronic health conditions such as heart or lung disease or diabetes.
No vaccine is 100% effective, but they are far better than not getting a vaccine. The benefits are greater than the risks.
Has the AstraZeneca COVID-19 vaccine been linked to adverse reactions like blood clots?
Here is what we know as of March 30, 2021. This will be updated as information becomes available.
- The AstraZeneca COVID-19 vaccine is highly effective at preventing severe COVID-19 illness and hospitalization.
- Health Canada is reviewing evidence of rare blood clots (called pro-thrombotic immune thrombocytopenia (VIPIT)) in adults under the age of 55 in Europe. The National Advisory Committee on Immunization (NACI) is recommending an immediate pause in the use of the AstraZeneca vaccine in all individuals less than 55 years of age in Canada while the safety review is conducted.
- In alignment with updated NACI recommendations Ontario will not be using the AstraZeneca vaccine for individuals under 55, while the data are being reviewed by Health Canada.
- Talk to your health care provider about getting the COVID-19 vaccine. They know your health conditions and can give you the best information to help you make your decision.
- While an adverse event may occur soon after vaccination, this does not mean that it was caused by the vaccine, which is why such events are carefully reviewed to determine if any action should be taken. More about Canada’s on-going vaccine safety monitoring process: https://www.canada.ca/en/public-health/services/diseases/2019-novel-coro...
- Health Canada continues to work closely with international regulators to gather and assess the information available to determine whether there is a need to address risks related to the vaccine.
Is there long-term evidence on potential harms?
As part of the vaccine safety program in Canada, ongoing, careful monitoring of the COVID-19 vaccines will continue. Very careful and continuous post-marketing tracking of those vaccinated will be carried out by the healthcare and public health systems at local, provincial and national levels. There is also longer-term follow-up of those who were vaccinated as part of the clinical trials. Health Canada has committed to being transparent with this monitoring of vaccine safety.
Have people died from the COVID-19 vaccine?
Below is what we know as of January 28, 2021.
The World Health Organization recently reviewed a number of cases of elderly people who died after being vaccinated in Norway and concluded the vaccines did not cause their deaths. The COVID-19 virus has caused millions of deaths around the world.
Over 40 million doses of vaccine have been administered globally, mostly to older populations, including those in long-term care. At this time, we have not heard of similar deaths in older adults in Canada, the United States, or the U.K. through adverse event reporting.
The Vaccine Adverse Event Reporting System (VAERS) is a national vaccine safety surveillance program run by CDC in the United States. A recent article published in The Journal of the American Medical Association reported on allergic reactions including anaphylaxis after the first dose of Pfizer-BioNTech COVID-19 vaccine using VAERS data from December 14–23, 2020. Of the 1,893,360 people vaccinated in this time period, 21 cases of anaphylaxis were reported. The data showed no reported fatalities linked to COVID-19 vaccinations. [Source: MMWR Early Release: https://www.cdc.gov/mmwr/volumes/70/wr/mm7002e1.htm]
Health Canada recently launched a new website with weekly reports on vaccine safety that lists how many people experience non-serious events, like soreness at the injection site, and serious events, like severe allergic reactions.
Has the vaccine demonstrated any adverse effects that disproportionately affect certain groups?
Not that we know of. Findings from the Pfizer-BioNTech clinical trials did indicate that while the vaccines seem to be just as effective in older adult participants, people 65 and older experienced fewer side effects than younger volunteers. Researchers are still studying why this is the case. Otherwise, there has been no indication from clinical trial findings or real-world vaccinations to date that certain populations are disproportionality affected by adverse events following vaccination.
Can I get the COVID-19 virus from the vaccine?
The vaccines will not make you sick with COVID-19. None of the approved vaccines contains a live version of the COVID-19 virus. Instead all the vaccines either deliver, or cause our bodies to make, harmless spike proteins only found on the surface of the COVID-19 virus and teaches your body how to spot and respond to this protein so when the real virus comes along, the body can fight it off.
How do I report an adverse reaction to the vaccine?
Severe reactions are uncommon. If you need medical assistance, please seek medical attention. Call 911 if you need assistance immediately.
Signs of serious allergic reactions may include:
- difficulty breathing
- swelling of face, throat or tongue
- hives (bumps on the skin that are itchy)
If these occur, a doctor should report them to Hamilton Public Health Services.
Other uncommon adverse reactions that doctors need to report to Hamilton Public Health Services include:
- swelling of arm that spreads to the next joint (elbow) or lasts 4 days or more
- pain that lasts 4 days or more
- fainting that causes injury
- swelling of the face or mouth
- very pale colour and serious drowsiness
- high fever (over 40°C)
- convulsions or seizures
- other serious symptoms (e.g., “pins and needles” or numbness lasting for over 24 hours).
- Discuss any of the uncommon reactions with your family doctor. If you don’t have a family doctor, a walk-in clinic might be preferred. A doctor can diagnose these uncommon reactions and report them to public health. If you do not have access to a doctor, please call Hamilton Public Health Services Vaccine program at 905-546-2424 ext. 7556 to report symptoms.
Read more about adverse effects (PDF, 135 KB)
Considerations for those with health conditions
I have other health conditions. How can I be sure the vaccine is safe?
Can people who have autoimmune disorders or are immunocompromised get the vaccines?
There is limited information on the use of COVID-19 vaccines in people who have autoimmune disorders and people who are immunocompromised. It is possible that the vaccine will have decreased effectiveness due to immunosuppression.
Immunosuppressed individuals in the authorized age group (16+ for Pfizer BioNTech vaccine; 18+ for Moderna vaccine) with autoimmune conditions, immunodeficiency conditions, or those immunosuppressed due to disease or treatment may choose to receive the vaccine after speaking to a health care provider about the risks, benefits, and lack of specific research data.
Individuals who are immunosuppressed due to disease or treatment or with an autoimmune condition, should consult their treating provider to discuss getting the COVID-19 vaccines.
For additional information on rheumatology, consult the Canadian Rheumatology Association statement on COVID-19 vaccination.
For additional information on inflammatory bowel disease, consult the Canadian Association of Gastroenterology statement on COVID-19 vaccination.
Can people who have allergies get the vaccines?
Individuals who have ever had a severe allergic reaction (i.e. anaphylaxis) to a previous dose of an mRNA vaccine or to any of its components (listed below) or its container, should not get either mRNA COVID-19 vaccine.
Individuals who have a suspected hypersensitivity or have had an immediate allergic reaction to:
- a previous dose of an mRNA COVID-19 vaccine
- any of components of the mRNA COVID-19 vaccine (including polyethylene glycol [PEG])
should not get mRNA COVID-19 vaccine unless they have been evaluated by an allergist-immunologist and it is determined that the person can safely receive the vaccine.
Individuals who have had a severe allergic reaction (i.e., anaphylaxis) to other vaccines or injectable therapies, must be evaluated by an allergist-immunologist before getting the COVID-19 vaccines so that a thorough risk/benefit discussion can take place and vaccination safety plan developed.
Individuals who have had an immediate allergic reaction to other vaccines or injectable therapies must discuss the risks and benefits of vaccination with their treating health care provider. In some cases, your treating health care provider may consult with an allergist-immunologist.
Individuals with a history of severe allergic reactions (i.e. anaphylaxis) not related to vaccines or injectable medications (for example, allergies to food, pet, venom, environmental, or latex, etc.) may choose to have the COVID-19 vaccines. The vaccination clinic will monitor you for 30 minutes following vaccination. With an extended period of observation following vaccination (30 minutes).
Ingredients in available COVID-19 vaccines
Pfizer-BioNTech Vaccine Ingredients:
- mRNA (medicinal ingredient)
- ALC-0315 = (4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate)
- ALC-0159 = 2-[(polyethylene glycol)-2000]-N, N-ditetradecylacetamide
- dibasic sodium phosphate dehydrate
- monobasic potassium phosphate
Moderna Vaccine Ingredients:
- mRNA (medicinal ingredient)
- 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)
- acetic acid, cholesterol, lipid SM-102
- tromethamine, tromethamine hydrochloride
- sodium acetate, sucrose, and water for injection
Note: Polyethylene glycol (PEG) is in both vaccines. It can also be found in laxatives, makeup, skin care products, personal lubricants, toothpastes, and some contact lenses. It is also in cough syrup, and in some food and drinks.
If you are unsure of the ingredients you are allergic to, talk to your health care provider.
Can people who are pregnant or breastfeeding get vaccinated?
There is limited information on the use of COVID-19 vaccines in pregnant people and people who are breastfeeding.
The current recommendation is that people who are pregnant in the authorized age group (16+ for Pfizer BioNTech vaccine; 18+ for Moderna vaccine) may choose to receive the COVID-19 mRNA vaccine after speaking with their treating health care provider on the risks and benefits to the individual and consent.
For additional information on COVID-19 vaccination in pregnancy: Society of obstetricians and gynecologists of Canada Statement on COVID-19 Vaccination in Pregnancy
There is limited information on the use of COVID-19 vaccines while breastfeeding. mRNA vaccines do not contain live virus. Based on how mRNA vaccines work in the body, scientists do not believe there is a risk to the breastfeeding infant.
Breastfeeding individuals in the authorized age group (16+ for Pfizer BioNTech vaccine; 18+ for Moderna vaccine) may choose to receive the COVID-19 mRNA vaccine after speaking to a health care provider about the risks, benefits, and lack of specific research data.
These questions and answers were developed in collaboration with Hamilton's Vaccine Readiness Network.
Simplifying the science of vaccines
- COVID-19 vaccine: What you need to know (Ottawa Public Health)
- COVID-19: How vaccines are developed (Health Canada)
- Vaccine safety in Canada (Health Canada)
- Vaccine safety (Immunize Canada)
- COVID-19 vaccines (World Health Organization)
- Understanding how vaccines work (Yale School of Medicine)
- Vaccine hesitancy (Immunize Canada)
- COVID-19 vaccine (Dr. Evan Adams)
- Moderna vaccine creation
- COVID-19 vaccines (Public Health Ontario)
- How COVID-19 mRNA vaccines work (Health Canada)
- Answering patient questions about COVID-19 vaccines (Centre for Effective Practice)
Understanding mRNA vaccines
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