Normal Reactions to Vaccines

These drugs are made using parts of the diseases they protect your child from, but they don’t cause the disease itself. They tell your child’s body to make blood proteins called antibodies to fight off those diseases. For example, after a vaccine for whooping cough, if your child were to come into contact with the real illness, their body would recognize it and have the right tools to attack it.

Mild reactions after a vaccine show that it’s working. These symptoms are a sign that your child’s body is making new antibodies. Normally, these reactions go away on their own within a few days. The most common effects you might see include:

• Tenderness or redness at the shot site
• Slight swelling at the shot site
• Fussiness
• Low-grade fever
• Trouble or excessive sleeping

• Swelling of one whole leg or arm

Much less common reactions include:

• Vomiting
• Drowsiness
• Loss of appetite

These are also normal side effects that should go away without any kind of treatment. Ask your doctor about appropriate dosing of pain and fever reducers.

When to Call the Doctor

If your child is allergic to certain vaccines, you’d notice signs that something is wrong. Typically, these reactions happen quickly after a vaccine, within a few minutes or hours.

A good rule of thumb is to watch for anything that seems unusual, like mood or behavior change, high fever, or weakness. Severe reactions are rare. Only 1 in 1 million children have them. Still, it’s important to know what symptoms your doctor needs to know about, so you can get help for your child.

Some specific signs to look for include:

• Breathing problems like wheezing
• Hoarseness
• Hives
• Pale color
• Weakness
• Fast heartbeat
• Dizziness
• Swelling in the face or throat
• Fever over 105 F
• Seizures

In extremely rare cases, some vaccines may lead to coma, long-term seizures, or permanent brain damage. These are unlikely reactions. In fact, doctors are trying to find out whether these and other serious side effects were caused by vaccines or for other reasons.

If you notice any serious symptoms that concern you after your child’s vaccines, call 911 or get your child to a hospital right away.