• 1 week ago

Post-Vaccination Reactions in Infants and Children

What Are Post-Vaccination Reactions?

Vaccines work by teaching the immune system to recognize and fight dangerous diseases. As a result, it’s common for the body to show mild and temporary symptoms after a vaccine—signs that the immune system is doing its job.

Most reactions are not dangerous and resolve quickly. Knowing what to expect helps parents avoid unnecessary worry and recognize the rare cases that require medical attention.

Common Post-Vaccine Reactions (and What to Do)

These are expected in the first 24–48 hours after vaccination and usually resolve on their own.

1. Mild Fever

  • Temperature between 38–38.5°C (100.4–101.3°F) is common
  • Especially after DTaP, MMR, or meningococcal vaccines
  • Usually lasts 1–2 days

What to do:

  • Offer fluids and dress your child lightly
  • Use paracetamol (acetaminophen) if over 38.5°C
  • Monitor for other symptoms

2. Fussiness and Drowsiness

  • Your child may be cranky, tired, or eat less than usual
  • These symptoms are normal and often peak within 24 hours

What to do:

  • Offer comfort: cuddles, nursing, calm environment
  • Allow extra naps or quiet time
  • Maintain gentle routines

3. Redness or Swelling at the Injection Site

  • Small area (1–2 cm) of redness, warmth, or a firm lump is common
  • Can last several days, especially after DTaP

What to do:

  • Apply a cool cloth to reduce swelling
  • Do not massage the area
  • If redness spreads or becomes hot and painful, consult your doctor

4. Mild Diarrhea After Rotavirus Vaccine

  • Since this is a live oral vaccine, it may cause loose stools
  • May last 1–3 days but does not affect hydration in most cases

What to do:

  • Ensure continued fluid intake
  • Monitor for signs of dehydration (dry lips, less urine)

Rare but Serious Reactions: When to Call a Doctor

While serious vaccine reactions are very rare, it’s important to know when to seek medical care.

Symptom

Reason to Worry

Fever above 38.5°C for more than 2 days

May indicate infection or adverse reaction

Uncontrollable crying > 3 hours

Possible sign of high fever or discomfort

Widespread rash or hives

Possible allergic reaction

Breathing difficulty

Emergency—seek help immediately

Severe fatigue or limpness

Watch closely; may indicate system stress

Refusal to feed or constant vomiting

Could be a red flag

What About Anaphylaxis?

Anaphylaxis is a very rare but serious allergic reaction—occurring in about 1 in 1,000,000 vaccine doses. It usually develops within 15–30 minutes after vaccination.

Signs of Anaphylaxis:

  • Swelling of lips, tongue, or eyes
  • Difficulty breathing or wheezing
  • Fast heartbeat, pale skin, or fainting
  • Hives or widespread rash

Why wait at the clinic?

All vaccination centers are equipped to respond to anaphylaxis. That’s why a 15–20 minute observation period is recommended after each vaccine.

Home Care Tips After Vaccination

  • Avoid massaging the injection area
  • Let your child rest as much as needed
  • A lukewarm bath is okay, but avoid long, hot soaks on the same day
  • Offer frequent fluids and light foods
  • Keep track of symptoms and contact your doctor if concerned

Follow-Up with Dr. Ekin Pasinlioğlu

  • Pre-vaccine consultation and consent process
  • Post-vaccine monitoring advice and availability
  • Individual follow-up for high-risk children
  • Recording and reporting any adverse effects
  • Support for anxious parents with evidence-based reassurance