Frequently asked questions about COVID-19 Vaccines
Updated May 12, 2021
COVID-19 vaccines authorized by Health Canada
What are mRNA vaccines?
Messenger RNA (mRNA) is found in all our cells and mRNA act as a “recipe” or a set of instructions that tells our cells on how to make proteins. Both Pfizer-BioNTech and Moderna COVID-19 vaccines use mRNA that enables our cells to make a certain protein that allows our immune system to develop antibodies. This eventually helps prevent and fight off a COVID-19 infection. The mRNA does not interact with or alter human DNA. The mRNA vaccine is eventually degraded and excreted out of our bodies within days to weeks from the time of immunization. These mRNA vaccines are not live vaccines and cannot cause COVID-19 infection.
Can COVID-19 vaccines be given with other vaccines?
COVID-19 vaccines should not be given simultaneously with other vaccines. If another vaccine is needed around the time of a COVID-19 vaccine, the following is recommended by Canada’s National Advisory Committee on Immunization (NACI):
BEFORE a COVID-19 vaccine: Wait for a period of at least 14 days after the administration of another vaccine before administrating a COVID-19 vaccine
AFTER a COVID-19 vaccine: Wait for a period of at least 28 days after a COVID-19 vaccine before receiving any another vaccine (except in the case where another vaccine is required for post- exposure prophylaxis)
Can COVID-19 vaccines be given to those with bleeding disorders or on a blood thinner?
Individuals receiving long-term blood thinners (such as Warfarin, Aspirin, Eliquis, Xarelto, Pradaxa) are not considered to be at higher risk of bleeding complications following immunization and may be safely immunized without stopping their blood thinner
For individuals with bleeding disorders, the condition should be optimally managed prior to immunization to minimize the risk of bleeding.
Are there any drug interactions with any of the COVID-19 vaccines?
Drug interaction studies have not been performed with the vaccines yet. Since the vaccines target the immune system, we would not expect them to interact with a majority of medications. Certain immunosuppressants may slightly reduce how effective the COVID-19 vaccine may be. There is also some evidence that taking Tylenol or Advil immediately BEFORE receiving a vaccine may potentially reduce the immune response. Therefore it is recommended that individuals should not take Tylenol or Advil immediately before receiving the COVID-19 vaccine. It would be okay to take Tylenol or Advil AFTER vaccination if needed to help with pain or mild fever. There are no drug interactions that would cause harm with any of the COVID vaccines.
Can I complete a TB skin test around the time of a COVID-19 vaccine?
The COIVID-19 vaccines may temporarily affect your immune system which may affect a TB skin test result. In general, it is recommended that TB skin tests be completed and read before COVID-19 immunization or delayed for at least 4 weeks after immunization. As long as all steps of a TB skin test are completed, a COVID-19 vaccine can be administered anytime afterward.
Can COVID-19 vaccines be given to those with severe allergies?
The COVID-19 vaccines should not be given to individuals with a history of anaphylaxis (or a severe life-threatening allergy) after previous administration of the COVID-19 vaccine. This means that individuals who had an anaphylactic reaction (or severe allergy) to the first dose of the COVID-19 vaccine should not receive the second dose and should be referred to an allergist. The COVID-19 vaccines should also not be given to individuals with a known severe allergy to one of the components of the vaccines or its packaging (see below for ingredient list). One potential allergen in the mRNA COVID-19 vaccines is polyethylene glycol. Having an allergy to polyethylene glycol is rare and this is found in many cosmetics and over-the-counter medications such as Restoralax, Laxaday, and many others. Any other history of allergic reaction to other non-COVID-19 vaccines, medications, food, insect venom, environmental allergens does not increase the risk of developing an allergy to the COVID-19 vaccines. As with any new vaccine, there is a baseline risk of developing a severe allergy which is rare with the COVID-19 vaccines. Out of all the vaccine doses administered in Canada, the rate of serious adverse reaction is 0.006%.
Pfizer-BioNTech 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, 1,2- distearoyl-sn-glycero-3-phosphocholine, cholesterol, dibasic sodium phosphate dehydrate, monobasic potassium phosphate, potassium chloride, sodium chloride, sucrose, water for injection. Rubber stopper is not made with natural rubber latex.
Moderna non-medicinal ingredients: 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), acetic acid, cholesterol, lipid SM-102, PEG2000 DMG, sodium acetate, sucrose, tromethamine, tromethamine hydrochloride, water for injection. Stopper does not contain natural rubber latex.
AstraZeneca non-medicinal ingredients: Disodium edetate dihydrate (EDTA), Ethanol, L-Histidine, L- Histidine hydrochloride monohydrate, Magnesium chloride hexahydrate, Polysorbate 80, Sodium chloride, Sucrose, Water for injection. Stopper does not contain natural rubber latex (elastomeric stopper).
Can individuals who are immunocompromised or immunosuppressed receive the COVID-19 vaccine?
There is currently no data on COVID-19 vaccination in immunosuppressed individuals. All of the available COVID-19 vaccines are non-live, non-replicating vaccines and would not cause infection or disease in someone who is immunocompromised or immunosuppressed. Immunocompromised persons, including individuals receiving immunosuppressant therapy, may have a diminished immune response to the vaccine.
Can the COVID-19 vaccine be given in pregnancy or breastfeeding?
There are ongoing studies to determine the safety and efficacy of COVID-19 vaccines in pregnancy and during breastfeeding. The Society of Obstetricians and Gynaecologists of Canada (SOGC) recognize that individuals who are pregnant are at increased risk of complications from COVID-19 infection. Studies show that pregnant women who are infected with COVID-19 are more likely to be admitted to a hospital or require admission to an intensive care unit (ICU) compared to those who are not pregnant. The SOGC supports the use of all available COVID-19 vaccines approved in Canada in any trimester of pregnancy and during breastfeeding.
What are vaccine induced blood clots?
The AstraZeneca vaccine and Janssen/Johnson & Johnson vaccine have been associated with rare blood clots called Vaccine-Induced immune Thrombotic Thrombocytopenia (VITT) which was previously called vaccine-induced prothrombotic immune thrombocytopenia (VIPIT). This complication may occur between 4-28 days after vaccination. At this time there’s no evidence that VITT would be more common in individuals who had a previous blood clot, have a family history of blood clots, have low platelets, or are pregnant. The incidence of VITT is roughly 1 in every 100,000 people vaccinated for the AstraZeneca vaccine and 1 in every 500,000 for the Janssen/Johnson & Johnson vaccine. If you received the AstraZeneca vaccine between 4 and 28 days ago and experience the following symptoms, please contact your health care professional or visit the closest emergency department: a severe headache that does not go away; seizure; difficulty moving any part of your body; new blurry vision or double vision that does not go away; difficulty speaking; shortness of breath; severe chest, back, or abdominal pain; unusual bleeding or bruising; new reddish or purplish spots, or blood blisters; or new severe swelling, pain, or colour change of an arm or a leg.