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Immunization Reactions

Reactions to vaccines are common and almost always harmless. Severe allergic (anaphylactic) reactions to vaccines are extremely rare. Listed below are the symptoms for a severe allergic reaction as well as common reactions to specific vaccines.

What should I do if my child has a severe allergic reaction?

A severe reaction is very rare. If it does happen, it is almost always within 20 minutes after the immunization. Seek help immediately or call 911 if you notice the following severe allergic reactions:

  • Trouble breathing
  • Weakness
  • Wheezing
  • Fast heartbeat
  • Hives
  • Dizziness
  • Paleness
  • Swelling of the throat

What are the possible reactions to the different vaccines?

Any vaccine can cause a child to faint. It is due to the process of getting a shot and not the vaccine ingredients. It may help if your child lies down for 15 minutes after receiving a vaccine.

Diphtheria-Tetanus-Pertussis Vaccine (DTaP)

  • Pain, tenderness, swelling, or redness at the injection site is the main side effect. It lasts for 3 to 7 days (between 2 to 5 children in 10 have this reaction). Give your child ibuprofen or acetaminophen and place a cold, wet washcloth over the tender area.
  • Fever for 24 to 48 hours (about 1 child in 4 has this reaction). Give your child ibuprofen or acetaminophen if the fever is over 102°F (38.9°C). The next time your child gets a DTaP shot, give your child acetaminophen at your healthcare provider's office and continue the medicine every 4 to 6 hours for 24 hours.
  • Mild drowsiness (about 1 child in 10 has this reaction), poor appetite (1 child in 10) for 24 to 48 hours, or crying for more than 3 hours (about 1 child in 1,000).
  • A large swelling (over 4 inches) of the arm or leg can follow the 4th or 5th dose of DTaP (about 1 child in 20). Most children can still move the leg or arm normally. The swelling resolves without treatment in 3 to 7 days. This is not an allergy and future DTaP vaccines are safe to give.
  • Painless lump at the injection site 1 or 2 weeks later. The lump is harmless and will disappear in about 2 months. Call your provider within 24 hours if it turns red or is tender.

CALL YOUR PROVIDER IMMEDIATELY IF the following rare but serious reactions occur:

  • Fever over 105°F (about 1 child in 16,000)
  • Crying for more than 3 hours (about 1 child in 1,000)
  • Seizures (about 1 child in 14,000)
  • Any other unusual reaction

Measles, Mumps, Rubella Vaccine (MMR)

These reactions may begin 5 to 12 days after getting the vaccine:

  • Fever (about 1 child in 6). Give your child ibuprofen or acetaminophen if the fever is over 102°F (38.9°C). Call your provider within 24 hours if the fever lasts over 72 hours or is over 104°F (40°C).
  • A mild pink rash mainly on the body (about 1 child in 20) may occur 1 to 6 weeks after getting the MMR vaccine. No treatment is necessary. The rash will last 2 to 3 days. Call your provider immediately if the rash changes to purple spots. Call within 24 hours if the rash becomes itchy or the rash lasts more than 3 days.
  • Swollen lymph glands (about 1 child in 75), and pain or stiffness in the joints that can last from a few days to a few weeks (about 1 child in 4) This problem is more common in teens and adults who receive the MMR.
  • Low blood platelet counts that lead to bruising and bleeding into the skin (about 1 child in 30,000). The risk of this happening from the wild-type measles disease is much greater than the risk from the vaccine.

The MMR vaccine does not cause autism.

Polio Vaccine (IPV)

  • Sore injection site (rare). No treatment is necessary. Giving your child ibuprofen or acetaminophen and placing a cold, wet washcloth over the tender area may provide some relief.
  • Fever (between 1 to 4 children in 100). Give your child ibuprofen or acetaminophen if the fever is over 102°F (38.9°C).

Pneumococcal Conjugate Vaccine (PCV13)

  • Fever, usually, mild (about 1 child in 3). Give your child ibuprofen or acetaminophen if the fever is over 102°F (38.9°C).
  • Redness, tenderness, or swelling at the shot site (about 1 child in 3). Giving your child ibuprofen or acetaminophen and placing a cold, wet washcloth over the tender area may provide some relief.

Haemophilus Influenza Type B Vaccine (Hib)

Most children who get this vaccine have no reactions to it.

  • Sore injection site (about 1 child in 4)
  • Mild fever (about 1 child in 20). Giving your child ibuprofen or acetaminophen and placing a cold, wet washcloth over the tender area may provide some relief.

Hepatitis B Vaccine (Hep B)

Most children who get this vaccine have no reactions to it.

  • Sore injection site (3 to 29 children in 100). Giving your child ibuprofen or acetaminophen and placing a cold, wet washcloth over the tender area may provide some relief.
  • Fever (less than 1 child in 10). Give your child ibuprofen or acetaminophen if the fever is over 102°F (38.9°C).

Chickenpox Vaccine (VAR)

Never give your child aspirin for any symptom within 6 weeks of receiving the vaccine. (Reye's syndrome has been linked with the use of aspirin to treat fever or pain caused by a virus.) For fever or pain, give ibuprofen or acetaminophen.

  • Pain or swelling at the injection site for 1 to 2 days (about 1 child in 5). A low-grade fever can also occur during this time.
  • Fever that begins 2 to 4 weeks after the vaccination and lasts 1 to 3 days (about 15 children in 100). Give your child ibuprofen or acetaminophen if the fever is over 102°F (38.9°C).
  • Mild rash at the injection site or elsewhere on the body (about 1 child in 30). The rash begins 5 to 26 days after the vaccine, looks like 2 to 10 chickenpox sores, and usually lasts a few days.

Children with these rashes can go to day care or school. If the vaccine rash contains fluid, cover it with clothing or a Band-Aid. Avoid school if there are widespread, weepy sores (because this may be real chickenpox).

Hepatitis A Virus (HAV) Vaccine

  • Sore injection shot site (about 2 children in 10). Giving your child ibuprofen or acetaminophen and placing a cold, wet washcloth over the tender area may provide some relief.
  • Headache or fatigue (less than 1 child in 20).

Influenza Virus Vaccine (Injection)

  • Pain, tenderness, or swelling at the injection site within 6 to 8 hours. Giving your child ibuprofen or acetaminophen and placing a cold, wet washcloth over the tender area may provide some relief.
  • Fever of 101°F to 103°F, or 38.3°C to 39.5°C. Fevers mainly occur in young children. Give your child acetaminophen or ibuprofen for fever over 102°F (38.9°C).

Influenza Virus Vaccine (Intranasal)

The nasal spray flu vaccine is not recommended for the 2017 flu season. Some children who get the nasal spray form of the flu vaccine will have symptoms such as:

  • A runny nose, congestion, and cough
  • Headache or muscle aches
  • A stomachache, and sometimes vomiting or diarrhea
  • Fever. Give your child acetaminophen or ibuprofen for fever over 102°F (38.9°C).

These symptoms do not last long and go away on their own.

Meningococcal Conjugate Vaccine (MCV4)

  • Pain, soreness at the vaccination site (about 1 child in 2). Giving your child ibuprofen or acetaminophen and placing a cold, wet washcloth over the tender area may provide some relief.
  • Fever and headache are other minor reactions that can occur.
  • Painful joints (about 1 child in 15)
  • Decrease in appetite (about 1 child in 8)
  • Guillain-Barré syndrome is a very rare but serious side effect. The vaccine never causes meningitis.

Human Papillomavirus Virus Vaccine (HPV)

  • Pain at the injection site (8 to about 9 children in 10)
  • Redness and swelling (about 3 to 4 children in 10)
  • Headache (about 3 children in 10)

Fainting is very rare after receiving a vaccine. Anyone receiving a vaccine should be observed for 15 minutes after the shot.

Written by Robert M. Brayden, MD, Professor of Clinical Pediatrics, University of Colorado School of Medicine.
Pediatric Advisor 2019.4 published by Change Healthcare.
Last modified: 2018-05-09
Last reviewed: 2018-05-09
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
© 2018 Change Healthcare LLC and/or one of its subsidiaries
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