Birth Vaccines
Hepatitis B Vaccine Side Effects in Babies
A slightly sore thigh and, occasionally, a brief mild fever — most newborns barely notice the hepatitis B vaccine.
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
- Within 24 hours of birth (thigh)
- Later doses
- 6, 10 & 14 weeks (in pentavalent)
- Protects against
- Hepatitis B liver infection
- Typical reaction
- Mild soreness ± brief low fever
- Usually settles in
- 1–2 days
The hepatitis B vaccine is usually your baby's very first injection, given in the thigh within 24 hours of birth. It protects against the hepatitis B virus — an infection that can silently damage the liver for life, and which is most dangerous when caught in infancy.
For such an important vaccine, its side effects are refreshingly mild. Most newborns have little more than a tender spot on the thigh, and many parents notice nothing at all. Knowing the small number of normal reactions — and the rare warning signs — helps you relax through those first newborn days.
What the hepatitis B vaccine is
The hepatitis B vaccine is an inactivated (non-live) vaccine — it contains a single purified protein from the virus's surface and cannot cause hepatitis. The birth dose is followed by further doses at 6, 10 and 14 weeks, usually inside the pentavalent (5-in-1) combination vaccine.
The birth dose matters because hepatitis B caught around birth becomes a chronic, lifelong infection in up to 9 out of 10 infected newborns. Vaccinating in the first 24 hours closes that window — which is why hospitals give it before you go home.
Common hepatitis B vaccine side effects
Soreness at the injection site
The thigh where the shot was given can be mildly tender for a day or so. Your baby may briefly cry when the area is touched or during nappy changes.
A small red spot or slight swelling
A pea-sized area of redness or firmness at the site is common and fades over a couple of days. A small painless lump can occasionally linger for a week or two as it settles.
Low-grade fever
A mild temperature (below about 38.5°C) in the first 24 hours affects a minority of babies and passes quickly.
Sleepiness or mild fussiness
Some newborns are a little sleepier or fussier than usual on vaccination day. Extra cuddles and feeds are all that's needed.
Slightly reduced feeding for a few hours
A brief dip in appetite on the day of the shot can happen; feeding should return to normal within a day.
What's usually normal after the hepatitis B vaccine
- Brief crying at the time of the injection, settling with feeding or skin-to-skin contact.
- A tender thigh or a small red mark at the injection spot for 1–2 days.
- A mild temperature in the first 24 hours that responds to simple measures.
- Extra sleepiness or mild fussiness on the day of the vaccine.
- A small, painless lump under the skin at the site that fades over days to a couple of weeks.
- Normal feeding, wet nappies and alertness returning by the next day.
How long side effects last
- Soreness and redness at the site: usually 1–2 days.
- Low-grade fever: typically within the first 24 hours, settling on its own.
- Sleepiness or fussiness: usually gone by the next day.
- A small firm lump at the injection site: can take 1–2 weeks to fully disappear and is harmless if painless and shrinking.
Home care tips
Comfort & soothing
- Feed on demand — breastfeeding during or right after injections measurably reduces newborn pain.
- Use skin-to-skin contact and gentle rocking to settle fussiness.
- Avoid pressing or massaging the injection spot; hold and carry your baby normally.
Fever & the injection site
- Dress your baby in light, comfortable layers — don't bundle a warm baby in extra blankets.
- A cool (not icy), clean, damp cloth held gently on the site for a few minutes can ease soreness.
- For a newborn, always call your doctor before giving any fever medicine — paracetamol dosing at this age needs medical guidance.
Warning signs — see a doctor urgently
Serious reactions are very rare, but a newborn showing any of these needs urgent assessment:
Seek urgent medical care if your child has
- Any fever of 38°C or higher in a baby under 3 months old — in a newborn, fever always deserves same-day medical review, whatever the cause.
- Signs of a severe allergic reaction: difficulty breathing, swelling of the face or lips, widespread hives, or sudden paleness and floppiness (usually within minutes to an hour of the shot).
- A baby who is very hard to wake, unusually floppy, or crying inconsolably for more than a few hours.
- Poor feeding with fewer wet nappies than usual, or any signs of dehydration.
- Spreading redness, warmth or pus at the injection site.
Call your doctor immediately — or go straight to the nearest emergency department.
🩺 Find a paediatricianTrouble breathing, facial swelling or unresponsiveness means emergency care now — go to the nearest hospital.
When to call your paediatrician
- Fever that returns or persists beyond 24–48 hours.
- The injection-site lump grows, becomes hot or increasingly painful instead of fading.
- Feeding stays reduced beyond the first day.
- Your baby seems 'not quite right' to you and you want reassurance — with a newborn, calling early is always reasonable.
Frequently asked questions
Why is the hepatitis B vaccine given on the first day of life?
Because hepatitis B infection caught around birth almost always becomes chronic and can silently damage the liver for decades. The birth dose blocks that window of risk — it's one of the most valuable single doses on the whole schedule.
Can the hepatitis B vaccine give my baby hepatitis?
No. The vaccine contains only a single purified surface protein of the virus, not the virus itself. It cannot cause hepatitis B infection.
There's a small lump on my baby's thigh a week after the shot. Is that okay?
A small, painless, slowly shrinking lump under the skin is a common, harmless reaction to injected vaccines and can take a week or two to disappear. See your doctor if it grows, turns red and hot, or seems painful.
My newborn has a fever after the vaccine. Can I give paracetamol?
For babies under 3 months, always speak to your doctor before giving any medicine, and treat a temperature of 38°C or above as a reason for same-day review. Newborn fever needs medical assessment even when a vaccine seems the likely cause.
My baby missed the birth dose. Is it too late?
No — the series can be started or caught up at the next visit, and protection will still build well. Tell your paediatrician so they can plan the catch-up doses.
Your next steps
Track your baby's vaccines
Enter your baby's birth date to get a personalised vaccine timeline with reminders, so no dose slips.
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 — Hepatitis B vaccines position paper
- CDC — Hepatitis B vaccination
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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