Should Your Child See a Doctor?

Immunization Reactions


  • 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 1 to 2 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 for Immunization Reactions

Call 911 If…

  • Your child has difficulty with breathing or swallowing
  • Your child is not moving or very weak
  • Your child is 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 (2.5 cm)

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
  • Fever returns after gone for over 24 hours
  • 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

Home Care Advice for Immunization Reactions

Treatment for Common Immunization Reactions

  1. Reassurance:
    • All of these reactions mean the vaccine is working.
    • Your child's body is creating new antibodies to protect against the real disease.
    • Most of these symptoms will only last 2 or 3 days.
  2. 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 for 20 minutes each hour as needed.
    • Pain Medicine: Give acetaminophen (e.g., Tylenol) or ibuprofen by mouth. (See Dosage table)
    • Localized Hives: Apply 1% hydrocortisone cream (no prescription needed) once or twice.
  3. 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).
  4. 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.
  5. 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 child 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 usually 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 hepatitis B vaccine should be examined.
  6. Influenza (Seasonal or H1N1) 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 (Seasonal or H1N1) Vaccine: Congested or runny nose, mild fever.
  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. Papillomavirus Vaccine:
    • No serious reactions reported
    • Sore injection sites for few days in 80%
    • Mild redness and swelling at the injection site in 25%
    • Fever over 100.4° F (38° C) in 10% and fever over 102° F (39° C) in 1% to 2%
  11. 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
  12. Polio Vaccine:
    • Polio vaccine by injection occasionally causes some muscle soreness.
    • Oral vaccine no longer used in the U.S.
  13. Rotavirus Vaccine:  
    • No serious reactions to this oral vaccine
    • Mild diarrhea or vomiting for 1 to 2 days in 3%
    • No fever

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


  1. AAP Committee on Infectious Diseases. Prevention and control of meningococcal disease: recommendations for use of meningococcal vaccines in pediatric patients. Pediatrics. 2005;116 (2): 496-505.
  2. American Academy of Pediatrics, Committee on Infectious Diseases. Immunization of preterm and low birth weight infants. Pediatrics. 2003; 112 (1):193-198.
  3. American Academy of Pediatrics: Committee on Infectious Diseases. Immunization Reactions. In Pickering L, ed. 2009 Red Book. 28th ed. Elk Grove Village, IL: 2009.
  4. Bohlke K, Davis RL, Marcy SM, et al. Risk of anaphylaxis after vaccination of children and adolescents. Pediatrics. 2003;112:815-820.
  5. Feder HM, et al. Clinical varicella following varicella vaccination: Don't be fooled. Pediatrics. 1997;89:897-898.
  6. Puwada L, et al. Systemic reactions (anaphylaxis) to measles-mumps-rubella vaccine and skin testing. Pediatrics. 1993;91:835-836.
  7. Rennels MB, Deloria MA, Pichichero ME, Losonsky GA, et al. Extensive swelling after booster doses of acellular pertussis-tetanus-diptheria vaccines. Pediatrics. 2000;105 (1). URL:  
  8. Schuval S. Avoiding allergic reactions to childhood vaccines (and what to do when they occur). Contemp Pediatr. 2003;20 (4):29-53.
  9. Skowronski DM, Remple VP, Macnabb J, et al. Injection-site reactions to booster doses of acellular pertussis vaccine:rate, severity and anticipated impact. Pediatrics. 2003;112:e453-e459.


This information is not intended to 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.

Copyright 1994-2015 Barton D. Schmitt, MD. All rights reserved.