Symptom Definition

  • You believe your child is having a reaction to an immunization.
  • Reactions to DTaP (Diphtheria, Tetanus, Pertussis), MMR (Measles, Mumps, Rubella), polio, Hemophilus influenzae type b, Hepatitis A, Hepatitis B, influenza, chickenpox (varicella)), pneumococcal and pneumococcusmeningococcal vaccines are covered.
  • Most reactions at the injection site and fever occur within 2 days and most general reactions or fever within 7 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


Call 911 Now (your child may need an ambulance)

  • 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 less than 12 weeks with fever above 100.4°F (38°C) rectally.  (Exception: occurs within 48 hours after DTaP shot.)
  • Fever above 104°F.  
  • High-pitched, unusual cry present for more than 1 hour.
  • Crying continuously for more than 3 hours.
  • Redness or red streak around the injection site bigger than 1 inch.  
  • Redness around the injection site persists for more than 48 hours (2 days).

Call Your Doctor Within 24 Hours (between 9am and 4pm) If

  • You think your child needs to be seen.
  • Fever present for more than 3 days.  
  • Pain, tenderness, or swelling at the injection site persists for more than 3 days.
  • Measles vaccine rash (onset day 6 to 12) persists for more than 3 days.

Call Your Doctor During Weekday Office Hours If

  • You have other questions or concerns.

Parent Care at Home If

  • Normal immunization reaction and you don't think your child needs to be seen.


  1. Local Reaction to the Injection (all vaccines except oral polio):
    • Pain:  For initial pain or tenderness at the injection site:
      • Apply ice to the area for 20 minutes once.
      • Give acetaminophen (e.g. Tylenol) or ibuprofen by mouth.
    • Fever:  For fevers above 102°F (39°C), give acetaminophen (ok to use ibuprofen if older than 6 months old).
    • 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.
    • Call Your Doctor If
      • Fever lasts more than 3 days.
      • Pain lasts more than 3 days.
      • Injection site starts to look infected.
      • Your child becomes worse or develops any of the "Call Your Doctor" symptoms.
  2. Chickenpox Vaccine:
    • Pain or swelling at the injection site for 1 to 2 days (in 19% of children).
    • Fever lasting 1 to 3 days begins 17 to 28 days after the vaccine (in 14%).
      Give acetaminophen (e.g. Tylenol) or ibuprofen for fever above 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.
  3. 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.Swollen arm or leg following 4th or 5th DTaP occur in 3% and is not serious.
    • 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.
  4. Hemophilus influenzae Type b Vaccine(HiB): 
    • No serious reactions reported.
    • Sore injection site or mild fever only occurs in 1.5% of children.
  5. 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.
  6. 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 less than 3 months with a fever following the vaccine should be examined.
  7. Influenza Virus Vaccine:
    • Pain, tenderness or swelling at the injection site occurs within 6 to 8 hours in 10% of children.
    • Fever 101° to 103°F (38.4° to 39.5°C) occurs in 18% of children.  Fevers mainly occur in young children.
  8. 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.  The fever is usually between 101° and 103°F (38.4° and 39.5°C) 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 more than 3 days.
  9. Meningococcal Vaccine: 
    • No serious reactions
    • Sore injection site for 1 to 2 days is uncommon
  10. Mumps or Rubella Vaccine:
    • There are no reactions except for an occasional sore injection site.
  11. Pneumococcus Vaccine:
    • Pain, tenderness, swelling OR redness at the injection site in 15-30%.
    • Mild fever below 102°F (39°C) in 15% for 1-2 days.      
    • No serious reactions.
  12. Polio Vaccine:
    • There are no serious reactions to oral polio vaccine.  Polio vaccine by injection occasionally causes some muscle soreness.

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.

Pediatric HouseCalls Online. Copyright © 2000-2004 Barton Schmitt, M.D. FAAP

Reviewed 8/2004

Revised 8/2004

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