Frequently asked questions about vaccines for the prevention of COVID-19

 

COVID-19 is a disease caused by a coronavirus called SARS-CoV-2. In some people, COVID-19 can progress from a sore throat to pneumonia, to a severe disease that can be fatal. Older people and people with underlying health conditions—including high blood pressure, diabetes, high cholesterol levels, lung disease and obesity—are at high risk of severe disease if they become infected with SARS-CoV-2.

Highly effective vaccines have been developed that can reduce the risk for developing COVID-19 and are gradually being made available. All vaccines must be expert reviewed and approved by Health Canada before they become available for use in Canada.

Here are answers to some common questions that you may have about COVID-19 vaccines. If you have other questions, please consult your healthcare provider and/or local public health authorities.

Why should I get vaccinated?

Vaccination is highly effective at preventing people from getting COVID-19. If people are vaccinated and still get infected with the virus that causes COVID-19, the vaccine reduces the risk of developing severe disease. It can also help to prevent transmission of the virus to others.

If you are unsure about getting the vaccine speak to your healthcare provider.

Where can I get a COVID-19 vaccine?

Check with your local public health authorities about the availability of the vaccines, and when and where you will be able to get vaccinated.

How do COVID-19 vaccines work and what vaccines are available in Canada?

The vaccines work by teaching your body’s immune system to recognize the virus that causes COVID-19. This allows your body to fight off the virus if it ever encounters it. Vaccines can reduce the severity of disease if you become infected, and they can also help to prevent transmission of the virus to others.

The following vaccines are approved in Canada:

  • Moderna COVID-19 vaccine – two doses separated by 28 days
  • Pfizer-BioNTech COVID-19 vaccine – two doses separated by 21 days
  • AstraZeneca COVID-19 vaccine – two doses separated by 4 to 12 weeks
  • Janssen COVID-19 vaccine – one dose

The Moderna and Pfizer-BioNTech vaccines use a tiny piece of the virus’s genetic material, called mRNA, to cause the body to produce small amounts of coronavirus proteins. These proteins help to train immune cells to recognize a specific part of the virus that causes COVID-19. The AstraZeneca and Janssen vaccines use a harmless virus, called an adenovirus, to train immune cells to recognize a specific part of the virus that causes COVID-19. Adenovirus vaccines have already been developed for other infections.

Other vaccines are also being studied and new vaccines will be approved over time. For the most recent information on approved COVID-19 vaccines and how they work, visit COVID-19 Vaccines: Authorized vaccines - Canada.ca

Can I get COVID-19 from the vaccine?

No. COVID vaccines do not contain the virus that causes COVID-19 and they cannot give you COVID-19.

How effective are the vaccines?

All approved vaccines demonstrated high efficacy at preventing COVID 19 disease in research studies:

  • Moderna –  94% effective at preventing symptomatic COVID-19 disease starting a couple of weeks after the second dose
  • Pfizer-BioNTech – 95% effective at preventing symptomatic COVID-19 disease starting a couple of weeks after the second dose
  • AstraZeneca COVID-19 vaccine – 59.5% effective at preventing symptomatic COVID-19 disease starting a couple of weeks after the second dose
  • Janssen COVID-19 vaccine – 66% effective at preventing symptomatic COVID-19 disease starting a couple of weeks after vaccination

For vaccines that require two doses, both doses of the vaccines are needed to achieve optimal effectiveness. In rolling out the vaccines quickly, some jurisdictions are trying a more flexible approach to the timing between doses in order to maximize coverage. The research studies used to demonstrate the efficacy of the vaccines for approval did not look at the effect of changing the timing between doses although there is growing evidence that this can be safely done with some COVID-19 vaccines. Delaying the second dose by a few months is not expected to result in lower vaccine efficacy after the second dose. In general, the immune system shows a better response to most vaccines when doses are delayed.

Researchers expect that the vaccines will also be effective at preventing transmission of the virus that causes COVID-19. Further studies are underway to determine how effective the vaccines are at preventing transmission of the virus.

How long does protection last?

The vaccines were tested for only a few months in clinical trials, so the duration of protection is not certain. The vaccine manufacturers are monitoring people who were vaccinated in the clinical trials to see how long protection lasts.

Are the vaccines safe?

Yes. COVID-19 vaccines were found to be generally safe in clinical trials.

It is normal to have some side effects after vaccination. In clinical trials, common side effects associated with the vaccines included the following:

  • pain at the injection site
  • fatigue
  • headache
  • muscle pain
  • joint pain
  • fever

In clinical trials, many people did not develop side effects, and those who did had very mild to moderate symptoms which resolved within a few days. Having these short-term symptoms is a sign that your immune system is responding to the vaccine. In about one in 100 people (1%) these symptoms were more severe.

Very rare side effects

There have been reports of very rare cases of serious blood clots with the AstraZeneca COVID-19 vaccine, primarily in women under the age of 55. These reports are currently under investigation as a possible rare side effect of the vaccine. The condition causing the blood clots is treatable. Health Canada advises that people who have been vaccinated with AstraZeneca COVID-19 vaccine (also manufactured under the name COVISHIELD) should seek immediate medical attention if they develop the following symptoms:

  • shortness of breath
  • chest pain,
  • leg swelling
  • persistent abdominal pain

Health Canada adds that, anyone with neurological symptoms including sudden onset of severe or persistent worsening headaches or blurred vision several days after vaccination, or who experiences skin bruising (other than at the site of vaccination) or petechiae [these are small red dots on the whites of the eyes or eyelids] starting a few days or more after vaccination, should seek prompt medical attention.

For further information visit: https://www.canada.ca/en/public-health/services/immunization/national-advisory-committee-on-immunization-naci/rapid-response-recommended-use-astrazeneca-covid-19-vaccine-younger-adults.html

Can the vaccine cause a severe allergic reaction?

In extremely rare cases, the vaccine can cause an immediate severe allergic reaction called anaphylaxis. If this occurs, onsite medical intervention can resolve the reaction.

The risk of a severe allergic reaction to the mRNA vaccines is as follows:

  • Moderna – about 2.5 per 1 million people
  • Pfizer-BioNTech – about 4.7 per million people

During clinical trials there were no reports of severe allergic reactions to the AstraZeneca or Janssen vaccines. However, this does not mean that such a reaction cannot happen.

After vaccination you will be asked to wait 15 minutes at the vaccination location in case a rare serious allergic reaction occurs. People who have a history of severe allergic reactions will be asked to wait for 30 minutes after being vaccinated.

Can I get the vaccine if I have a history of allergic reactions?

If you have a history of severe allergies to medicines, foods, insect stings, animals or plants, talk to your healthcare provider about COVID-19 vaccination. Healthcare providers can help you make a decision about whether or not to get the vaccine and what can be done should a serious allergic reaction occur.

At the vaccination site, tell the healthcare provider about your history of allergic reactions. Vaccination sites are prepared for intervening should a rare serious allergic reaction occur.

After vaccination everyone will be asked to wait at least 15 minutes at the vaccination site in case a rare serious allergic reaction occurs. If you have a history of severe allergic reactions, you will be asked to wait for 30 minutes after being vaccinated.

I had a severe allergic reaction to the first shot of the vaccine, should I get the second?

The U.S. Centers for Disease Control recommends that people who have had a severe allergic reaction to the first shot of the vaccine should not receive the second dose.

Do I need to get vaccinated if I have already had COVID?

It is unclear how long natural immunity lasts and there have been well-documented cases of re-infection in people who have recovered from COVID-19. Therefore, researchers recommended vaccination for people who have had COVID-19.

Do I need to get both doses of the vaccine?

Both doses are necessary to achieve the levels of protection seen in clinical trials. The vaccination site where you receive your first dose of the vaccine will let you know when to come back for your second dose.

Once I’ve been vaccinated should I stop taking precautions such as physical distancing, wearing masks and so on?

People who have been vaccinated should still follow public health guidelines for prevention, including wearing face masks, physical distancing and frequent hand washing. Researchers do not yet know how effective the vaccines are at preventing transmission of the virus.

Will the vaccine protect me against new variants of SARS-CoV-2?

The virus that causes COVID-19 can change its structure or mutate. Many variants of SARS-CoV-2 are emerging now and are likely to emerge in the future. To date, it appears that the current vaccines approved in Canada still provide some protection against the emerging variants of concern, and will likely provide protection from developing severe disease if you become infected with one of the variants. Should a new vaccine or a booster shot become necessary because of new variants of SARS-CoV-2, public health authorities will issue guidance.

Can I get the vaccine if I have HIV?

It is important to consider getting vaccinated if you have HIV. Many people with HIV have or are at an increased risk for developing the underlying conditions that increase their chances of developing COVID-19 or severe disease if they become infected with the virus that causes COVID-19. These underlying conditions include high blood pressure, diabetes, high cholesterol levels, lung disease, obesity and so on. 

Experts consider COVID vaccines to be safe and effective for people with HIV. Clinical trials with the Moderna, Pfizer-BioNTech and AstraZeneca vaccines included a relatively small number of people with HIV, all of whom were taking ART and who were healthy and well. Further studies are needed to determine if the vaccine works as well for people with HIV as it does for the general population.

There is no information yet on how well the vaccine works in people living with HIV who have a compromised immune system. If you are not on treatment and have a very low CD4 count, discuss vaccination with your healthcare provider. Some experts recommend starting HIV treatment first to prevent HIV-related complications and to potentially improve vaccine effectiveness.

Can I get the vaccine if I have hepatitis B, C and/or liver disease?

It is important to consider getting vaccinated if you have hepatitis B, C or liver disease. Many people with chronic hepatitis infections have liver injury and underlying conditions that increase their chances of developing COVID-19 or severe disease if they become infected with the virus that causes COVID-19. Researchers consider the vaccine to be safe and effective for people with hepatitis B and C and other liver diseases such as fatty liver. There is no evidence that the vaccine makes liver disease worse.

Can I get the vaccine if I have had facial fillers?

The American Society for Dermatologic Surgery (ASDS) has reviewed evidence from the clinical trials of the Moderna and Pfizer-BioNTech vaccines. They recommend that “patients already treated with dermal fillers should not be discouraged or precluded from receiving vaccines of any kind. Similarly, patients who have had vaccines should not be precluded from receiving dermal fillers in the future.”

The U.S. Food and Drug Administration (FDA) found that there were three cases of facial or lip swelling in people who had dermal fillers who received the Moderna vaccine. All cases happened in women aged 29 to 51. The reactions happened one to two days after vaccination. The reactions were serious but not life-threatening and in all cases the reactions resolved. Two of the women had the fillers implanted two to six weeks prior to vaccination. No data was available for the third person. In one case, a patient had a similar reaction in the past when she had been vaccinated with the annual flu vaccine. It is not clear how many other people in the clinical trial also had dermal fillers.

No data about side effects from the AstraZeneca or Janssen vaccines on facial fillers is available.

The information on this page is based on available research related to the transmission and prevention of COVID-19. This resource will be updated as new evidence emerges. Last updated April 7, 2021.

—Sean R. Hosein

Acknowledgement

CATIE thanks the following infectious disease specialists for their input, research assistance and helpful comments in developing this resource: Isaac Bogoch MD, University of Toronto, William Cameron MD, University of Ottawa, and Michaeline McGuinty MD, University of Ottawa.

Resources

Vaccines for COVID-19: Authorized vaccines — Health Canada

Vaccine safety, concerns and possible side effects Health Canada

TreatmentUpdate 239 CATIE

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