Birth Vaccines
BCG Vaccine Side Effects in Babies
A small sore that slowly turns into a scar over weeks is the normal BCG reaction — keep it clean and dry, and let it heal on its own.
Written and fact-checked by the ParentVibes editorial team against WHO, IAP, CDC and NHS immunisation guidance. Not yet reviewed by a named clinician.
Quick facts
- Usually given
- At birth, left upper arm
- Protects against
- Severe childhood TB
- Typical reaction
- Small sore → crust → scar
- Reaction starts
- 2–6 weeks after the shot
- Heals by
- Around 2–3 months (a scar remains)
The BCG (Bacillus Calmette–Guérin) vaccine is one of the very first vaccines your baby receives — usually in the hospital within a day or two of birth. It protects against the most severe forms of childhood tuberculosis, including TB meningitis.
BCG is unusual among vaccines: instead of a quick, invisible immune response, it causes a slow, visible skin reaction at the injection site that unfolds over weeks. Many parents worry when a boil-like sore appears a month after the shot — but this delayed reaction is expected, and the little scar it leaves behind is the well-known sign of BCG protection that most Indian adults carry on their own arm.
What the BCG vaccine is
BCG is a live, weakened (attenuated) vaccine given as a single small injection into the top layer of skin, almost always on the left upper arm. In India it is part of the National Immunization Schedule and is given at birth or as early as possible in the first year.
Because it is injected into the skin itself rather than the muscle, the visible skin changes that follow are part of how this vaccine works — the immune system responds right there at the injection site.
No scar? Don't panic
A few healthy babies never develop a visible sore or scar. This does not automatically mean the vaccine failed — ask your paediatrician at a routine visit; routine re-vaccination is usually not needed.
Common BCG side effects
Almost everything parents notice after BCG happens at the injection site, on a slow timeline that is unique to this vaccine.
A small red bump, then a sore (2–6 weeks later)
A raised red spot appears at the injection site weeks after the shot. It may soften into a small pus-filled boil that oozes a little before crusting over. This delayed sore is the expected BCG reaction, not an infection from poor hygiene.
A crust that becomes a small scar
The sore dries into a crust and slowly heals over several weeks, leaving a flat or slightly dented scar about 2–8 mm across. The scar is permanent and harmless.
Mild tenderness at the site
The area can be slightly tender or itchy while it heals. Babies are rarely bothered by it once the first day or two have passed.
Slightly swollen glands near the armpit
Small, painless lymph nodes in the left armpit or neck can enlarge slightly as the immune system responds. Small nodes that don't grow are usually left alone and settle by themselves.
Brief low-grade fever (uncommon)
A mild fever in the first day or two is possible but much less common than with other baby vaccines. High fever is not expected after BCG — if it happens, look for another cause and check with your doctor.
What's usually normal after BCG
The BCG reaction looks worse than it is. These are the signs of a normal, healthy response:
- Nothing visible at all for the first 2–6 weeks — the quiet phase is normal.
- A red bump or small boil (up to about 1 cm) that appears weeks after the injection.
- A little pus or clear fluid oozing from the sore before it crusts.
- A crust that forms, falls off, and re-forms once or twice while healing.
- A small permanent scar once healing finishes — this is the expected end point.
- Your baby feeding, sleeping and behaving normally throughout.
| Time after BCG | What you'll typically see |
|---|---|
| 0–2 weeks | Little or nothing — sometimes a tiny raised mark |
| 2–6 weeks | Red bump appears, may soften into a small boil |
| 6–10 weeks | Sore oozes slightly, then crusts over |
| 2–3 months | Crust falls off, leaving a small flat scar |
How long BCG side effects last
- The full skin reaction — bump, sore, crust, scar — usually plays out over 2–3 months.
- Any single oozing phase typically lasts a few days to a couple of weeks.
- Mild tenderness settles within days; itchiness can come and go while the sore heals.
- Slightly enlarged armpit glands can take several weeks to settle.
- The scar itself is permanent — a normal, expected mark, not an ongoing side effect.
Slow is normal
BCG healing is measured in weeks, not days. As long as the sore is slowly improving and your baby is well, a long timeline on its own is not a concern.
Home care for the BCG site
The golden rule: keep it clean and dry, and let it heal on its own schedule.
Caring for the sore
- Keep the area clean and dry — plain water during baths is fine; pat dry gently.
- Leave the sore open to air when possible; if it oozes, cover loosely with dry gauze.
- Never squeeze the boil, pick the crust, or burst it — let it drain and heal naturally.
- Don't apply antiseptic creams, ointments, home remedies or powders unless your doctor advises it.
Comfort & clothing
- Dress your baby in loose, soft sleeves so fabric doesn't rub the site.
- Normal bathing is fine — just avoid scrubbing the injection area.
- Cuddle, feed and soothe as usual; no activity restrictions are needed.
Warning signs — see a doctor urgently
Serious BCG reactions are rare, but these signs need prompt medical review:
Seek urgent medical care if your child has
- An abscess — a large, hot, painful swelling at the injection site (bigger than about 2–3 cm).
- A sore that keeps draining pus for many weeks with no sign of healing.
- A large or rapidly growing lump in the armpit or neck (enlarged lymph node), especially if the skin over it turns red or it starts to drain.
- High fever, poor feeding, unusual drowsiness or your baby looking seriously unwell.
- Spreading redness or warmth around the injection site suggesting a skin infection.
- Any severe allergic reaction soon after the shot — difficulty breathing, facial swelling, or widespread rash (extremely rare; usually while still at the clinic).
Call your doctor immediately — or go straight to the nearest emergency department.
🩺 Find a paediatricianIf your baby is struggling to breathe, is floppy or unresponsive, go to the nearest emergency department immediately — don't wait for an appointment.
When to call your paediatrician
Not an emergency, but worth a call or a visit:
- The sore looks larger than a 1-rupee coin or seems to be getting worse instead of better after several weeks.
- You can feel a firm lump in the left armpit that seems to be growing over weeks.
- The site becomes increasingly red, warm or painful rather than slowly settling.
- No sore or scar has appeared by 6 months and you'd like it reviewed at a routine visit.
- You're unsure whether what you're seeing is the normal BCG reaction — a quick photo shared with your doctor often settles it.
Frequently asked questions
Is pus coming out of the BCG injection site normal?
Usually yes. A small boil that ooze a little pus 2–10 weeks after BCG is part of the expected reaction. Keep it clean and dry, don't squeeze it, and let it crust over. See a doctor if the swelling is large, hot and painful, or keeps draining for many weeks without improving.
My baby has no BCG scar. Did the vaccine fail?
Not necessarily. A small number of babies mount a good immune response without ever forming a visible scar. Mention it at a routine check-up — most guidelines do not recommend routine re-vaccination just because there's no scar.
Can I bathe my baby after the BCG vaccine?
Yes. Normal bathing is fine from day one. Just avoid scrubbing the injection site, and gently pat the area dry afterwards.
Why did the BCG reaction appear a month after the injection?
BCG is a live, weakened vaccine injected into the skin, and the immune response it triggers builds slowly. A bump or sore appearing 2–6 weeks later is the classic timeline — it's the vaccine working, not a delayed infection.
Should I put ointment or turmeric on the BCG sore?
No. Don't apply creams, antiseptics or home remedies unless your doctor specifically advises it. The sore heals best when kept clean, dry and untouched.
Does the BCG vaccine cause fever?
Fever is uncommon after BCG. A mild, brief temperature can happen, but a high or persistent fever is not a typical BCG reaction — check with your paediatrician, as another cause is more likely.
Your next steps
Track your baby's vaccines
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Open Vaccination TrackerVaccination schedule India
The full IAP-style immunisation chart from birth to the teen years, explained in plain language.
See the full scheduleFind a paediatrician
Worried about a reaction, or due for the next dose? Find a trusted paediatrician near you.
Find a pediatricianRelated vaccine guides
Sources
- WHO — Vaccine safety and side effects
- Indian Academy of Pediatrics (IAP) — Immunization guidelines
- CDC — Possible side effects from vaccines
- NHS — NHS vaccinations and when to have them
- WHO — BCG vaccine position paper
- NHS — BCG vaccine side effects
Next review due: 6 January 2027.
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Medical disclaimer
This page is educational information about common vaccine reactions and is not a substitute for medical advice, diagnosis or treatment. Every child is different — always follow the guidance of your paediatrician or vaccination centre. If your child has trouble breathing, swelling of the face or throat, a fast heartbeat, hives all over, dizziness or weakness soon after a vaccine, or seems seriously unwell at any point, seek emergency medical care immediately. When in doubt, always get your child checked — it is never a waste of anyone's time.
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