COVID-19: Effectiveness and benefits of vaccination

On this page

• Effectiveness of vaccination
• Variants of concern
• Recommended doses
• Follow public health measures
• Monitoring

Effectiveness of vaccination

Vaccination is one of the most effective ways to protect our families, communities and ourselves against COVID-19. Evidence indicates that the vaccines used in Canada are very effective at preventing severe illness, hospitalization and death from COVID-19.

The primary series of mRNA vaccines (Pfizer-BioNTech Comirnaty or Moderna Spikevax), plus a booster dose, offers better protection against Omicron infection and severe disease than the primary series alone. Among people who are vaccinated, studies show that:

• their level of protection against infection from the primary series decreases over time and is low against Omicron, but can be improved with a booster dose
• the primary series appears to maintain good protection against severe disease (such as hospitalization) caused by Omicron
• protection against severe disease is higher after a booster dose

Vaccination is very important, even if you've been previously infected with COVID-19. While infection alone provides some protection, vaccination after infection helps improve the immune response and may provide better and longer-lasting protection.

Risk factors for exposure and severe outcomes should be assessed when considering the timing of COVID-19 vaccination. Contact your local public health authority for more information on when you should get vaccinated after having COVID-19.

We continue to closely monitor the evolving science and research related to vaccine effectiveness.

Learn more about:

• COVID-19: Definition of primary series
• Vaccines for COVID-19: Booster doses
• COVID-19 variants of concern

Variants of concern

Viruses change over time. While most changes aren't significant, some can create new variants of concern.

Having as many people vaccinated as possible reduces the risk of ongoing circulation of the virus. That's because the circulation of the virus could result in the development of new variants of concern.

Learn more about:

• COVID-19 variants of concern

Recommended doses

For best protection against COVID-19, it's important to receive a primary series as well as a booster dose if you're eligible for it.

A primary series consists of either of the following:

• 2-dose series of any combination of the following vaccines:
  • Moderna Spikevax
  • Medicago Covifenz
  • Novavax Nuvaxovid
  • AstraZeneca Vaxzevria
  • Pfizer-BioNTech Comirnaty
• a single-dose Janssen (Johnson & Johnson) vaccine

It's important to return for your second dose. The National Advisory Committee on Immunization (NACI) recommends an 8-week interval between your first and second dose. This results in better protection than with a shorter time between doses.

People 18 years of age and over are eligible for a booster dose. NACI recommends that this booster dose be given at least 6 months after completion of the primary series.

Receiving all your recommended doses provides:

• very good protection against severe illness, hospitalization and death
• some protection against getting infected and becoming sick
  • this protection may decrease over time and isn't as effective for Omicron as with other variants

Learn more about:

• Vaccines for COVID-19: Who is eligible
• COVID-19 variants of concern
• Vaccines for COVID-19: Booster doses

Follow public health measures

Regardless of your vaccination status, continue to follow public health measures to help prevent the spread of COVID-19, including variants of concern.

Individual public health measures are most effective when layered together and include:

• staying home when sick
• wearing a well-fitting mask
  • choose the best quality and best fitting mask or respirator that's available to you
• improving indoor ventilation
• maximizing physical distance from others

If you develop symptoms of COVID-19:

• isolate yourself away from others and
• follow the advice of your local public health authority on testing and isolation requirements

Contact your health care provider if you have specific questions or concerns about your health.

Learn more about:

• COVID-19: Individual public health measures
• COVID-19 mask use: Advice for community settings
• COVID-19: Improving indoor ventilation
• COVID-19: Symptoms and treatment
• COVID-19: How to quarantine or isolate at home
• COVID-19: Contact your public health authority

Monitoring

Ongoing monitoring in Canada and around the world helps determine whether changes to the virus affect:

• transmission
• disease severity
• effectiveness of vaccines
• effectiveness of drug treatments
• ability of testing to detect the virus

Learn more about:

• Vaccines and treatments for COVID-19: Monitoring COVID-19 variants