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  • Immunization Reactions


    • You think your child is having a reaction to a recent immunization (vaccine)
    • Types of Reactions: Reactions at the shot site (such as pain, swelling, redness) and general reactions (such as a fever or being fussy)
    • Reactions to these vaccines are covered:
      • Chickenpox (varicella)
      • DTaP (Diphtheria, Tetanus, Pertussis)
      • Hemophilus influenzae type b
      • Hepatitis A
      • Hepatitis B
      • Human Papilloma virus
      • Influenza
      • MMR (Measles, Mumps, Rubella)
      • Meningococcal
      • Polio
      • Pneumococcal and
      • Rotavirus


    • Shot sites can have swelling, redness and pain. Most often, these symptoms start within 24 hours of the shot. They most often last 2 to 3 days. With the DTaP vaccine, they can last up to 7 days.
    • Fever with most vaccines begins within 24 hours and lasts 1 to 2 days.
    • With the MMR and chickenpox shots, fever and rash can occur. These symptoms start later. They usually begin between 1 and 4 weeks.
    • Severe allergic reactions are very rare, but can occur with any vaccine. They start within 2 hours.

    When to Call Us for Immunization Reactions

    Call 911 Now (your child may need an ambulance) If:

    • Trouble breathing or swallowing Not moving or very weak Can’t wake up
    • You think your child has a life-threatening emergency

    Call Us Now (night or day) If:

    • Your child looks or acts very sick
    • Hard to wake up
    • Age under 12 weeks old with fever. (Caution: Do NOT give your baby any fever medicine before being seen.)
    • Fever over 104°F (40°C)
    • High-pitched crying lasts more than 1 hour
    • Crying nonstop lasts more than 3 hours
    • You think your child needs to be seen urgently

    Call Us Within 24 Hours (between 9 am and 4 pm) If:

    • You think your child needs to be seen, but not urgently
    • Redness or red streak starts more than 48 hours (2 days) after the shot
    • Redness around the shot becomes larger than 3 inches (7.5 cm)
    • Fever lasts more than 3 days
    • Fever returns after gone for more than 24 hours
    • Measles vaccine rash (starts day 6 to 12 after shot) lasts more than 4 days

    Call Us During Weekday Office Hours If:

    • You have other questions or concerns
    • Redness or red streak around shot is larger than 1 inch (2.5 cm)
    • Redness, swelling or pain is getting worse after 3 days
    • Fussiness from vaccine lasts more than 3 days

    Parent Care at Home If:

    • Normal immunization reaction

    Care Advice for Immunization Reactions

    Treatment for Common Immunization Reactions

    What You Should Know:

    • Immunizations (vaccines) protect your child against serious diseases.
    • All of these reactions mean the vaccine is working.
    • Your child’s body is making new antibodies to protect against the real disease.
    • Most of these symptoms will only last 2 or 3 days.
    • There is no need to see your child’s doctor for normal reactions.
    • Medicine is only needed if your child has pain. Also, use a fever medicine for fever over 102°F (39°C).
    • Here is some care advice that should help.

    Reaction at Shot Site:

    • Cold Pack: For pain at the shot site, use a cold pack. You can also use put ice in a wet washcloth on the sore shot site. Use for 20 minutes as needed.
    • Pain Medicine: To help with the pain, give acetaminophen (such as Tylenol) or ibuprofen. Use as needed. See Dose Table.
    • Hives at the Shot Site: If itchy, can put on 1% hydrocortisone cream. No prescription is needed. Use twice daily as needed.


    • Fever with most vaccines begins within 12 hours and lasts 2 to 3 days. This is normal, harmless and possibly helpful.
    • For fevers above 102°F (39°C), give acetaminophen. If over 6 months old, can give ibuprofen. See Dose Tables.
    • For all fevers: Give extra fluids. Do not use too many clothes or blankets on your child.

    General Reaction:

    • All vaccines can cause mild fussiness, crying and restless sleep. This is usually due to a sore shot site.
    • Some children sleep more than usual. A decreased appetite and activity level are also common.
    • These symptoms are normal. They do not need any treatment.
    • They will usually go away in 24-48 hours.

    Call Your Doctor If:

    • Redness larger than 1 inch (2.5 cm) for first 3 DTaP shots or any other shot
    • Redness larger than 2 inches (5 cm) with 4th DTaP
    • Redness larger than 3 inches (7.5 cm) with 5th DTaP
    • Pain, swelling or redness gets worse after 3 days (or lasts more than 7 days)
    • Fever starts after 2 days (or lasts more than 3 days)
    • Your child becomes worse

    Specific Immunization Reactions

    Chickenpox Vaccine:

    • Pain or swelling at the shot site for 1 to 2 days. (20% of children)
    • Mild fever lasting 1 to 3 days begins 17 to 28 days after the shot (15%). Give acetaminophen or ibuprofen for fever over 102°F (39°C).
    • Never give aspirin for fever, pain or within 6 weeks of getting the shot. Reason: Risk of Reye syndrome, a rare but serious brain disease.
    • Chickenpox-like rash (usually 2 red bumps) at the shot site (3%)
    • Chickenpox-like rash (usually 5 red bumps) scattered over the body (4%)
    • This mild rash begins 5 to 26 days after the shot. Most often, it lasts a few days.
    • Children with these rashes can go to child care or school. (Reason: For practical purposes, vaccine rashes are not spread to others)
    • EXCEPTION: Do not go to school if red bumps drain fluid and are widespread. Reason: can be actual chickenpox.
    • Caution: If vaccine rash contains fluid, cover it with clothing or a Band-Aid.

    DTaP or DT Vaccine:

    • The following harmless reactions to DTaP can occur:
      • Pain, tenderness, swelling and redness at the shot site is the main side effect. This happens in 25% of children. It lasts for 3 to 7 days.
      • 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.
      • Large swelling over 4 inches (10 cm) arm can follow the later doses of DTaP. The area of redness is smaller. This usually occurs with the 4th or 5th dose. It occurs in 5% of children. Most children can still move the leg or arm normally. The area of redness is smaller.
      • The large thigh or upper arm swelling goes away without treatment by day 3 (60%) to day 7 (90%).
      • This is not an allergy. Future DTaP vaccines are safe to give.

    Hemophilus Influenza Type B Vaccine (Hib):

    • No serious reactions reported.
    • Sore injection site or mild fever only occurs in 2% of children.

    Hepatitis A Vaccine:

    • No serious reactions reported.
    • Sore injection occurs in 20% of children.
    • Loss of appetite occurs in 10% of children.
    • Headache occurs in 5% of children.
    • Most often, no fever is present.
    • If these symptoms occur, they most often last 1-2 days.

    Hepatitis B Virus Vaccine (HBV):

    • No serious reactions reported.
    • Sore shot site occurs in 30% of children and mild fever in 3% of children.
    • Fever from the vaccine is rare. Any baby under 2 months with a fever after this shot should be examined.

    Influenza Virus Vaccine:

    • Pain, tenderness or swelling at the injection site occurs within 6 to 8 hours. This happens in 10% of children.
    • Mild fever under 103°F (39.5°C) occurs in 20% of children. Fevers mainly occur in young children.
    • Nasal Influenza Vaccine: Congested or runny nose, mild fever.

    Measles Vaccine:

    • The measles shot can cause a fever (10% of children) and rash (5% of children). This occurs about 6 to 12 days after the shot.
    • 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 needed. The rash cannot be spread to others. Your child can go to child care or to school with the rash.
    • Call Your Doctor If:
      • Rash changes to blood-colored spots
      • Rash lasts more than 3 days

    Meningococcal Vaccine:

    • No serious reactions.
    • Sore shot site for 1 to 2 days occurs in 50%. Limited use of the arm occurs in 15% of children.
    • Mild fever occurs in 5%, headache in 40% and joint pain in 20%
    • The vaccine never causes meningitis.

    Mumps or Rubella Vaccine:

    • There are no serious reactions.
    • Sometimes, a sore shot site can occur.

    Papillomavirus Vaccine:

    • No serious reactions.
    • Sore injection site for few days in 80%.
    • Mild redness and swelling at the shot site (in 25%).
    • Fever over 100.4°F (38.0°C) in 10% and fever over 102°F (39°C) in 2%.
    • Headache in 30%.

    Pneumococcal Vaccine:

    • No serious reactions.
    • Pain, tenderness, swelling OR redness at the injection site in 20%.
    • Mild fever under 102°F (39°C) in 15% for 1-2 days.

    Polio Vaccine:

    • Polio vaccine given by shot sometimes causes some muscle soreness.
    • Polio vaccine given by mouth is no longer used in the U.S.

    Rotavirus Vaccine:

    • No serious reactions to this vaccine given by mouth.
    • Mild diarrhea or vomiting for 1 to 2 days in 3%.
    • No fever.

    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.
    Copyright 1994-2013 Barton D. Schmitt, M.D.

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