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Health 6 min read

Vaccination Side Effects in Babies: What to Expect and When to Worry

It's completely normal for babies to have some reaction after vaccines. Understanding what to expect can help you feel prepared and know when to seek medical attention.

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Common Side Effects (Normal)

These reactions are signs that the immune system is responding to the vaccine:

🌡️

Low-Grade Fever

Up to 102°F (38.9°C)

Duration: 24-48 hours
💉

Injection Site Reactions

Redness, swelling, soreness

Duration: 2-3 days
😢

Fussiness

Crying, irritability

Duration: 24-48 hours
😴

Sleepiness

More tired than usual

Duration: 1-2 days
🍼

Decreased Appetite

Less interest in feeding

Duration: 1-2 days
🤧

Mild Symptoms

Runny nose, mild rash

Duration: varies

How to Manage Side Effects

For Fever

  • Dress baby in light clothing
  • Keep room comfortable, not too warm
  • Offer more frequent feedings
  • Give acetaminophen (Tylenol) if over 2 months - follow dosing on package
  • Ibuprofen can be used after 6 months of age
Important: Do NOT give aspirin to babies or children. Always confirm medication dosage with your pediatrician.

For Injection Site Pain

  • Apply a clean, cool, damp cloth to the area
  • Move or exercise the arm/leg gently
  • Do NOT rub or massage the injection site

For Fussiness

  • Extra cuddling and comfort
  • Gentle rocking or swaying
  • Skin-to-skin contact
  • Quiet, calm environment

When to Call the Doctor

Contact your pediatrician if your baby experiences:

  • Fever over 104°F (40°C)
  • Fever lasting more than 3 days
  • Crying for 3+ hours that can't be consoled
  • Signs of allergic reaction:
    • Hives or rash spreading beyond injection site
    • Swelling of face, lips, or throat
    • Difficulty breathing
    • Unusual paleness
  • Seizures or unusual movements
  • Baby seems limp or unresponsive
Call 911 immediately if your baby has difficulty breathing, swelling of the face/throat, or becomes unresponsive.

Side Effects by Vaccine Type

DTaP (Diphtheria, Tetanus, Pertussis)

  • Most common to cause injection site reactions
  • Fussiness is common, especially after later doses
  • Slight fever possible

MMR (Measles, Mumps, Rubella)

  • Reactions may appear 7-12 days after vaccination
  • Mild rash possible
  • Temporary joint stiffness (rare)

Rotavirus (Oral)

  • Mild diarrhea or vomiting possible
  • Irritability
  • No injection site reaction (it's oral)

Flu Vaccine

  • Soreness at injection site
  • Low-grade fever
  • Mild body aches

Tips for Vaccination Day

  • Breastfeed during or right after - natural pain relief
  • Bring a comfort item - favorite toy or blanket
  • Stay calm - babies pick up on parent anxiety
  • Distract with singing or talking during the shot
  • Schedule wisely - not before major events or travel

Frequently Asked Questions

Can I give pain medicine before the vaccine?

Generally not recommended. Studies suggest giving acetaminophen before vaccines may reduce the immune response. Wait until after if pain relief is needed.

Is it safe to bathe my baby after vaccination?

Yes, bathing is fine. A lukewarm bath may even help soothe a fussy baby.

Should I skip vaccines if baby had a reaction before?

Mild reactions are not a reason to skip future vaccines. Discuss any concerns with your pediatrician, especially if there was a severe reaction.

Key Takeaways

  • Mild side effects are normal and expected
  • Most reactions resolve within 48-72 hours
  • Side effects mean the immune system is working
  • Serious reactions are extremely rare
  • Benefits of vaccination far outweigh the risks

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