After Your Vaccination

The following information was developed for this website by medical professionals and public health experts using Canadian government and other scientific and medical sources. It is not intended as medical advice. Always seek the advice of a qualified healthcare provider with any questions you may have regarding the COVID-19 vaccine.

We can’t say with certainty, but it is possible that you can still carry the virus even if you’re vaccinated. We do know that the vaccine will protect people from getting sick from the virus, but it’s possible that you could still carry the virus and be contagious to others even though you got your immunization. We will learn more as the clinical trials continue and real-world evidence emerges. In the meantime, we’ll need to continue wearing our masks, practice physical distancing, and keep following public health recommendations until enough Canadians are fully vaccinated.

It takes about two weeks after the second dose for the body to build immunity after vaccination. Someone could be infected with the virus just before or just after vaccination and get sick, because the vaccine didn’t have enough time to provide protection.

This is also why a full series of two doses of the vaccines are required.

The COVID-19 vaccines’ initial effectiveness is already very high after the first dose (80-92%) and lasts for at least a few months.

Experience with other multi-dose vaccinations after a single dose suggest persistent protection could last six months or longer. In fact, many studies have shown that you get an even better booster immune response the longer you wait. So this is backed by science.

And for most vaccines, antibody levels (immunity) will go down over time and do not suddenly fall below protective levels. Even months or years later, another vaccine dose can boost immunity to higher levels, giving a longer duration of protection.

Now that we have much more reliable vaccine supply in Canada, the timeline between doses has been decreased to eight weeks. 

Yes, for now, until the Public Health Agency of Canada determines when is the right time to do away with masking and distancing. This is because it takes several weeks for the vaccine to become effective (to build immunity) and maximum protection is only achieved after completion of the second dose of the Pfizer-BioNTech, Moderna and AstraZeneca COVID-19 vaccines, for as many people as possible.

We don’t know yet how long protection lasts for those who are vaccinated. Studies on the mRNA vaccines currently show that people who were vaccinated had a very strong immunity to COVID-19 for at least six months. It looks like immunity will last a while, but studies need to follow this over time.

At this point, we’re not sure if immunity will last a year or ten years, or if there will be a need for a booster shot at some point.

It usually takes a few weeks for the body to build immunity following COVID-19 vaccination. But remember that two doses are required in order to achieve the best immunity from the Pfizer-BioNTech, Moderna and AstraZeneca COVID-19 vaccines. The Johnson & Johnson COVID-19 vaccine only requires one dose.

After vaccination, it is common to have temporary mild or moderate side effects, including: 

  • Pain, redness, warmth, itching or swelling at the site of injection,
  • Fatigue,
  • Headache,
  • Nausea,
  • Muscle or joint pain, and
  • Mild fever or chills.

These are normal signs that your body is building protection and these symptoms should go away within a few days. 

If your symptoms are significant or worsening, consult your health care provider. If they are consistent with COVID-19, you should get tested and self-isolate until test results are available.

Very rarely, a more serious side effect called anaphylaxis may occur. This generally occurs within several minutes or the first hour after vaccination. For this reason, people receiving their COVID-19 vaccine are asked to remain for at least 15 minutes following vaccination so that health care personnel can monitor individuals for any serious reactions.

Side-effects are not an indication of whether or not the vaccine is working.

It is true that side effects are normal signs that the vaccine is working and your body is building protection. However, this doesn’t mean you should be worried if you don’t have side-effects. For example, the mRNA vaccines provided protective immunity to over 90% of recipients in the clinical trials, but more than 50% reported no side-effects. In other words, most people did not experience any reactions, but had full immunity.

So, if you didn’t feel any side effects after your COVID-19 vaccine, it’s not something to worry about—you still have the same protection as someone who experienced a side-effect!