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Pediatric - Immunization Reactions

Immunization reactions

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Does this describe your child's symptoms?

  • You believe your child is having a reaction to a recent immunization
  • Reactions to DTaP (Diphtheria, Tetanus, Pertussis), MMR (Measles, Mumps, Rubella), polio, Hemophilus influenzae type b, Hepatitis A, Hepatitis B, Influenza, Chickenpox (varicella), pneumococcal, meningococcal, Rotavirus and Human Papilloma virus vaccines are covered


  • Most local swelling, redness and pain at the injection site begins within 24 hours of the shot. It usually lasts 2 to 3 days, but with DTaP can last 7 days.
  • Fever with most vaccines begins within 24 hours and lasts 2 to 3 days.
  • With live vaccines (MMR and chickenpox), fever and systemic reactions usually begin between 1 and 4 weeks.
  • Severe allergic reactions are very rare, but can occur with any vaccine.
When to Call Your Doctor

Call 911 Now (your child may need an ambulance) If
  • Difficulty with breathing or swallowing
  • Not moving or very weak
  • Unresponsive or difficult to awaken
Call Your Doctor Now (night or day) If
  • Your child looks or acts very sick
  • Age under 12 weeks with fever above 100.4° F (38.0° C) rectally (Caution: Do NOT give your baby any fever medicine before being seen.)
  • Fever over 104° F (40° C) and not improved 2 hours after fever medicine
  • High-pitched, unusual crying present over 1 hour
  • Crying continuously for over 3 hours
  • Redness or red streaking around the injection site begins over 48 hours (2 days) after the shot
  • Redness or red streak around the injection site becomes larger than 1 inch
Call Your Doctor Within 24 Hours (between 9 am and 4 pm) If
  • You think your child needs to be seen
  • Fever present for more than 3 days
  • Measles vaccine rash (onset day 6 to 12) persists over 3 days
Call Your Doctor During Weekday Office Hours If
  • You have other questions or concerns
  • Pain, tenderness, redness or swelling at the injection site persists over 3 days
  • Fussiness from vaccine persists over 3 days
Parent Care at Home If
  • Normal immunization reaction and you don't think your child needs to be seen

Treatment for Common Immunization Reactions
  1. Local Reaction at Injection Site:
    • Cold Pack: For initial pain or tenderness at the injection site with any vaccine, apply a cold pack or ice in a wet washcloth to the area as needed.
    • Pain Medicine: Give acetaminophen (e.g., Tylenol) or ibuprofen by mouth. (See Dosage table)
    • Localized Hives: Apply 1% hydrocortisone cream OTC once or twice.
  2. Fever:
    • Fever with most vaccines begins within 24 hours and lasts 2 to 3 days.
    • For fevers above 102° F (39° C), give acetaminophen every 4 hours (If over 6 months old, okay to give ibuprofen every 6 hours) (See Dosage table)
    • For all fevers: Give cold fluids in unlimited amounts. Avoid excessive clothing or blankets (bundling).
  3. General Reaction:
    • All vaccines can cause mild fussiness, irritability and restless sleep. While this is usually due to a sore injection site, sometimes the cause is less clear.
    • Some children sleep more than usual. A decreased appetite and activity level are also common.
    • These symptoms do not need any treatment and will usually resolve in 24-48 hours.
  4. Call Your Doctor If:
    • Fever lasts over 3 days
    • Pain lasts over 3 days
    • Redness or swelling lasts over 3 days
    • Your child becomes worse
Specific Immunization Reactions
  1. Chickenpox Vaccine:
    • Pain or swelling at the injection site for 1 to 2 days (in 19% of children)
    • Mild fever lasting 1 to 3 days begins 17 to 28 days after the vaccine (in 14%). Give acetaminophen or ibuprofen for fever over 102° F (39°C).
    • Never give aspirin for fever, pain or within 6 weeks of receiving the vaccine (Reason: risk of Reye's syndrome - a rare but serious brain disease)
    • Chickenpox-like vaccine rash (usually 2 lesions) at the injection site (in 3%)
    • Chickenpox-like vaccine rash (usually 5 lesions) scattered over the body (in 4%)
    • This mild rash begins 5 to 26 days after the vaccine and usually lasts a few days.
    • Children with these vaccine rashes can go to day care or school. (Reason: for practical purposes, vaccine rashes are not contagious)
    • EXCEPTION: avoid school if widespread, weepy lesions (Reason: probably actual chickenpox).
    • Precaution: if vaccine rash contains fluid, cover it with clothing or Band-Aid.
  2. DTaP or DT Vaccine: The following harmless reactions to DTaP can occur:
    • Pain, tenderness, swelling or redness at the injection site (in 25% of children) and lasts for 24 to 48 hours.
    • Fever (in 25% of children) and lasts for 24 to 48 hours
    • Mild drowsiness (30%), fretfulness (30%) or poor appetite (10%) and lasts for 24 to 48 hours.
    • A large swelling over 4 inches (10 cm) arm can follow the 4th or 5th dose of DTaP occurs in 5% of children. Most children can still move the leg or arm normally.
    • The large thigh or upper arm swelling resolves without treatment by day 3 (60%) to day 7 (90%). This is not an allergy and future DTaP vaccines can be given.
  3. Hemophilus Influenza Type B Vaccine (Hib):
    • No serious reactions reported
    • Sore injection site or mild fever only occurs in 1.5% of children
  4. Hepatitis A Vaccine:
    • No serious reactions reported
    • Sore injection occurs in 20% of children, loss of appetite in 10%, and headache in 5%.
    • Usually no fever.
    • If these symptoms occur, they begin 3-5 days after vaccine and last 1-2 days
  5. Hepatitis B Virus Vaccine (HBV):
    • No serious reactions reported
    • Sore injection site occurs in 30% of children and mild fever in 3% of children
    • Because fever from the vaccine is rare, any infant under 2 months with a fever following the vaccine should be examined.
  6. Influenza Virus Vaccine:
    • Pain, tenderness or swelling at the injection site occurs within 6 to 8 hours in 10% of children.
    • Mild fever under 103° F (39.5° C) occurs in 18% of children. Fevers mainly occur in young children.
    • Nasal Influenza Vaccine: No side effects, no fever or symptoms.
  7. Measles Vaccine:
    • The measles vaccine can cause a fever (10% of children) and rash (5% of children) about 6 to 12 days following the injection.
    • Mild fever under 103° F (39.5°C) in 10% and lasts 2 or 3 days.
    • The mild pink rash is mainly on the trunk and lasts 2 or 3 days.
    • No treatment is necessary. Your child is not contagious.
    • Call Your Doctor If:
      • Rash becomes very itchy
      • Rash changes to purple spots
      • Rash lasts over 3 days
  8. Meningococcal Vaccine:
    • No serious reactions
    • Sore injection site for 1 to 2 days occurs in 50%, with limited use of the arm in 15%.
    • Mild fever occurs in 4%, headache in 40% and joint pain in 20%
    • The vaccine never causes meningitis.
  9. Mumps or Rubella Vaccine: There are no reactions except for an occasional sore injection site.
  10. Pneumococcus Vaccine:
    • No serious reactions
    • Pain, tenderness, swelling OR redness at the injection site in 15 - 30%
    • Mild fever under 102° F (39° C) in 15% for 1-2 days
  11. Polio Vaccine:
    • Polio vaccine by injection occasionally causes some muscle soreness.
    • Oral vaccine no longer used in the U.S.
  12. Rotavirus Vaccine:
    • No serious reactions to this oral vaccine
    • Mild diarrhea or vomiting for 1 to 2 days in 3%
    • No fever
  13. Human Papillomavirus Vaccine:
    • No serious reactions reported
    • Sore injection site for few days in 80%
    • Mild redness and swelling at the injection site (in 25%)
    • Fever over 100.4° F (38.0° C) in 10% and fever over 102° F (39° C) in 1-2%.

And remember, contact your doctor if your child develops any of the "Call Your Doctor" symptoms.

Disclaimer: This information is not intended be a substitute for professional medical advice. It is provided for educational purposes only. You assume full responsibility for how you choose to use this information.

Author and Senior Reviewer: Barton D. Schmitt, M.D.

Last Reviewed: 1/19/2009

Last Revised: 6/25/2008

Content Set: Pediatric HouseCalls Online

Copyright 1994-2009 Barton D. Schmitt, M.D.

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