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Symptoms after vaccination

CISSS de la Montérégie-Ouest

Symptoms after vaccination

Some symptoms may be caused by the vaccine. Other problems may occur by chance and are not related to the vaccine. Most reactions are harmless and do not last long. Reactions are less common among people age 55 and over.

Vaccines cannot cause COVID-19. However, people who have been in contact with the virus in the days preceding their vaccination could still develop COVID-19.

In most cases
(more than 50% of people)
- Pain at the injection site
Very often
(less than 50% of people)
- Headache, fatigue, fever or shivering
- Joint pain
- Muscle soreness
- Diarrhea, vomiting
- Swollen armpit lymph nodes
(less than 10% of people)
- Redness, swelling at the injection site
(less than 1 person in 1,000)

- Facial swelling


We recommend that you stay at the clinic for at least 15 minutes aftervaccination because allergic reactions may occur. If an allergic reaction occurs, the symptoms will appear a few minutes after the vaccination.

The person giving the vaccine will be able to treat this reaction immediately.

What to do after vaccination

Tips to follow immediately following vaccination

Wait 15 minutes before leaving premises where vaccine is received. If an allergic reaction occurs, the symptoms will appear a few minutes after the vaccination.

If you feel side effects, immediately inform the person giving the vaccine. That person will be able to treat you immediately.

Tips to follow at home

If you experience redness, pain or swelling at the injection site, apply a cold, damp compress on it.

Use medication for fever or discomfort if needed.

When to seek medical help

See a doctor if one of the following applies to you:

  • You experience serious and unusual symptoms
  • Your symptoms get worse instead of improving
  • Your symptoms last over 48 hours

If you have symptoms of COVID‑19, use the COVID‑19 Symptom Self-Assessment Tool to find out if you need to get tested.