Last updated: October 1, 2024

Learn what to expect after your immunization and how to manage common side effects, and when to seek medical attention.

On this page, you will find information on vaccine side effects, how to treat them and when to seek medical attention.

On this page:

• Side effects
• What can I do to feel better?
• Safety tips when using over-the-counter medicine for fever and pain
• When to seek medical attention
• Additional resources

Side effects

Most side effects are mild and go away after 1-2 days. Some vaccines may cause side effects that appear a bit later (e.g., 1-2 weeks after vaccination). For vaccine-specific side effects, read the HealthLink BC Files. Click on the vaccine name to view the HealthLinkBC File.

Here are some side effects you might have after some vaccines:

• Muscle and joint soreness
• Tiredness and headache
• Fever, chills and shivering
• Nausea, vomiting and diarrhea
• Pain, redness and swelling where the vaccine was given

Other Side effects for specific vaccines may include:

• After COVID-19 vaccines: swollen lymph nodes under armpit
• After MMR and varicella vaccines: fever, rash and other side effects may occur about 1-2 weeks after immunization
• After nasal spray flu vaccine: Nasal congestion and runny nose
• For infants and young children: Fussiness, crying, restlessness, and decreased appetite
• For school-age children and teens: Tiredness, muscle soreness, and occasional headache

What can I do to feel better?

For pain and swelling where the vaccine was given:

• For infants and young children:
  • Move your child’s arm or leg several times a day
  • Apply a cool, wet cloth or wrapped ice pack over the area where the vaccine was given
  • Give over-the-counter medicine if needed to help make your child comfortable
• For school-age children and teens:
  • Encourage your child to move their arm several times a day to reduce soreness
  • Apply a cool, wet cloth or ice pack over the injection site
  • Offer acetaminophen (Tylenol®) or ibuprofen (Advil®) to relieve discomfort
• For adults:
  • Move your arm several times a day to reduce soreness
  • Apply a cool, wet cloth or wrapped ice pack over the area where the vaccine was given
  • Take over-the-counter medicine, such as acetaminophen (Tylenol®) or ibuprofen (Advil®), to help reduce discomfort

For fever:

• Rest
• Drink lots of fluids
• Dress lightly
• Take over-the-counter medicine, such as ibuprofen (Advil®) or acetaminophen (Tylenol®) to help bring down the fever and reduce discomfort

Normal range of temperature by body site:

• Armpit: 36.5-37.5°C -> 37.6°C
• Mouth: 35.5-37.5°C -> 37.6°C
• Ear: 35.8-38°C -> 38.1°C
• Rectal: 36.6-38°C -> 38.1°C (Only use rectal thermometers if you are comfortable doing so and a health care provider has shown you how to use it safely.)

Safety tips when using over-the-counter medicine for fever and pain

Carefully read and follow all directions on the label. Do not take more than the recommended amount.

For infants and young children:

• Give acetaminophen (Children’s Tylenol®) or ibuprofen (Children’s Advil®) for pain or fever, but do not give ibuprofen to babies under 6 months unless directed by a healthcare professional

For school-age children and teens:

• Offer acetaminophen (Tylenol®) or ibuprofen (Advil®) to relieve aches, fever, or soreness
• Do not give ASA (Aspirin®) to children or teens under 18

For adults:

• Take acetaminophen (Tylenol®) or ibuprofen (Advil®) for pain or fever
• If you are pregnant, avoid using ibuprofen (Advil®) and opt for acetaminophen (Tylenol®) instead

When to seek medical attention

Serious side effects after immunization are very rare. But if they do happen, it is important to act. Report any serious or unexpected side effects after immunization to your health care provider.

Seek medical attention right away if you have:

• Signs or symptoms of a severe allergic reaction (for example, hives, difficulty breathing, or swelling of the throat, tongue, or lips). If this happens after you leave the clinic, call 9-1-1 or your local emergency number.
• A seizure lasting more than 3 minutes or if your child is having their first seizure.
• Fever:
  • If your child is less than 3 months old and has a fever
  • If your child is 3-12 months old with a fever of 39°C or higher lasting more than one day
  • If your child is less than 2 years and has a fever lasting more than 24 to 48 hours
  • If your child is older than 2 years and has a fever for more than 3 days
• For COVID-19 vaccines: Chest pain, shortness of breath, or a feeling of a fast, fluttering, or pounding heart
• For rotavirus vaccines: Repeated vomiting, a swollen tummy, or bloody stool
• In infants and young children: Dehydration, not eating or drinking, severe vomiting or diarrhea, weakness, pale skin, difficulty waking, or crying non-stop for a long time or longer than usual
• In school-age children: Dehydration, difficulty waking, very pale, weak, or has severe vomiting or diarrhea
• Any other worrisome signs or symptoms

Find your immunization record at Health Gateway.