Definition

• A reaction to a recent immunization (vaccine) shot
• Most reactions are at the injection site (such as pain, swelling, redness)
• General reactions (such as a fever or being fussy) also are common

Health Information

Symptoms

• Shot sites can have swelling, redness and pain. Most often, these symptoms start within 24 hours of the shot. They most often last 3 to 5 days. With the DTaP vaccine, they can last up to 7 days. This is a normal reaction to the vaccine, not an infection. It is usually the only side effect of the vaccine.
• In some children, severe swelling can occur with the 4th (15 months) DTaP shot. The swelling can be up to 2 inches (5 cm). Swelling up to 3 inches (7.5 cm) can normally occur with 5th (4 years) dose. This is not an allergic reaction. Future DTaP vaccines are safe to give.
• Any hives and itching around the shot site is normal. It does not mean your child is allergic to the vaccine.
• Fever with most vaccines begins within 24 hours and lasts 1 to 2 days.
• With the MMR and chickenpox shots, fever and rash occurs in 10% of children. 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.
• Abnormal reaction: A secondary bacterial infection at the shot site. This is very rare (less than 1 per 1000). Suspect if the redness or fever begins over 48 hours after the shot was given. Also, be on the lookout for redness or pain that increases after 3 days.

Causes

• The vaccines contain substances that turn on your immune system.
• About 25% of children have a skin reaction to the substances at the shot site.
• This happens most with the DTaP vaccine. However, it can happen with other vaccines, including the flu vaccine.
• It means the vaccine is doing what it is supposed to do.

Care Advice

1. Overview:
   1. Immunizations (vaccines) protect your child against serious diseases.
   2. All of these reactions mean the vaccine is working.
   3. Your child’s body is making new antibodies to protect against the real disease.
   4. There is no need to see your child’s doctor for normal reactions. Examples of normal reactions are redness around the shot site and fever. Redness and fever starting on day 1 of the shot is always normal.
   5. Here is some care advice that should help.
2. Reaction at Shot Site:
   1. Cold Pack: For pain at the shot site, use a cold pack. You can also put ice in a wet washcloth on the sore shot site. Use for 20 minutes as needed.
   2. Pain Medicine: To help with the pain, give acetaminophen (such as Tylenol) or ibuprofen. Use as needed.
   3. Hives at the Shot Site: If itchy, can put on 1% hydrocortisone cream. No prescription is needed. Use twice daily as needed.
3. Fever:
   1. Fever with most vaccines begins within 12 hours and lasts 2 to 3 days. This is normal, harmless and possibly helpful. Fevers may improve antibody production.
   2. For fevers above 102° F (39° C), give acetaminophen (such as Tylenol). If over 6 months old, can give ibuprofen.
   3. For all fevers: Give extra fluids. Keep your child well hydrated.
4. General Reactions:
   1. All vaccines can cause mild fussiness, crying and restless sleep. This is usually because of a sore shot site.
   2. Some children sleep more than usual. A decreased appetite and activity level are also common.
   3. These symptoms are normal. They do not need any treatment.
5. What to Expect:
   1. Most local reactions last 2 or 3 days.
   2. Most fever lasts 2 days.

Call Your Doctor If

• Redness starts after 2 days (48 hours)
• Redness becomes larger than 2 inches (5 cm)
• Pain or redness gets worse after 3 days
• Pain or redness lasts more than 7 days
• Fever starts after 2 days
• Fever lasts more than 3 days
• You think your child needs to be seen
• Your child becomes worse

Author: Barton Schmitt MD, FAAP

Copyright 2000-2020 Schmitt Pediatric Guidelines LLC

Disclaimer: This health information is for educational purposes only. You the reader assume full responsibility for how you choose to use it. The information contained in this handout should not be used as a substitute for the medical care and advice of your pediatrician. Listing of any resources does not imply an endorsement.

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