A newborn HepB shot is usually a 0.5 mL injection, started at birth and finished as a 3-dose series in the first year.
The hepatitis B vaccine (often written as HepB) is one of the first vaccines many babies receive. Parents tend to have the same questions: What is the actual dose? When is it given? What changes for preterm babies or when the birthing parent has hepatitis B?
This guide sticks to the practical stuff: dose volume, timing windows, common schedules, and the special steps hospitals take when there’s exposure risk.
Hepatitis B Vaccine Dose For Infants: Schedule And Volume Basics
For most full-term infants, the “dose” means the amount in the syringe. In the U.S., licensed single-antigen infant hepatitis B vaccines are given as a 0.5 mL intramuscular injection, usually in the thigh. Brands differ in antigen micrograms, yet the infant volume stays at 0.5 mL.
The routine series is three doses:
- Dose 1: Birth dose.
- Dose 2: 1–2 months of age.
- Dose 3: 6–18 months of age.
Birth dose timing: two common targets
“At birth” can mean different things depending on risk. Clinicians use two main timing targets:
- Within 24 hours: common routine timing when the birthing parent’s hepatitis B surface antigen (HBsAg) test is documented negative.
- Within 12 hours: used when the birthing parent is HBsAg-positive or the status is unknown at delivery.
That faster 12-hour window is often paired with hepatitis B immune globulin (HBIG) when exposure risk is confirmed or can’t be ruled out.
What the vaccine record tells you
Your baby’s immunization record can look like a receipt with extra codes. The parts that matter for parents are simple:
- Product name: often Engerix-B or Recombivax HB for infant single-antigen doses.
- Volume: usually 0.5 mL.
- Site: thigh muscle.
- Date: used to time the next dose with valid spacing.
When the birthing parent has hepatitis B
If the birthing parent is HBsAg-positive, the hospital treats the newborn’s first steps as post-exposure prevention. The baby receives both hepatitis B vaccine and HBIG. HBIG gives ready-made antibodies right away. The vaccine trains the baby’s immune system to make its own antibodies over time.
The timing details are laid out in CDC guidance for perinatal care. In practice, staff follow a simple plan:
- Give hepatitis B vaccine within 12 hours of birth.
- Give HBIG within 12 hours of birth.
- Finish the vaccine series on schedule.
- Do post-vaccination blood testing later in infancy after the series.
You can see the full timing grid by birth weight and maternal status on CDC’s perinatal hepatitis B vaccine administration page.
When status is unknown at delivery
Sometimes the lab result isn’t in the delivery record. In that case, hospitals move as if status is unknown: the baby gets the vaccine within 12 hours, and staff work to confirm the parent’s test result fast. If the result turns positive, HBIG is added on the timeline used for that birth-weight group.
| Infant situation | What happens at birth | How many HepB doses total |
|---|---|---|
| Full-term, birthing parent HBsAg-negative | HepB vaccine within 24 hours | 3 doses |
| Full-term, birthing parent HBsAg-positive | HepB vaccine + HBIG within 12 hours | 3 doses + later blood test |
| Full-term, status unknown | HepB vaccine within 12 hours; HBIG if status stays unknown or turns positive | 3 doses + blood test if exposed |
| Preterm < 2000 g, birthing parent HBsAg-negative | HepB vaccine at 1 month or discharge | 3 doses |
| Preterm < 2000 g, birthing parent HBsAg-positive | HepB vaccine + HBIG within 12 hours | 4 doses + later blood test |
| Preterm < 2000 g, status unknown | HepB vaccine within 12 hours; HBIG unless parent confirmed negative by 12 hours | 4 doses when early birth dose is given |
| Combination vaccines used after 6 weeks | Birth dose is single-antigen; combos start at 6 weeks+ | Often 4 doses recorded |
| Missed birth dose | Start as soon as possible, then finish with valid spacing | Full series still needed |
Preterm and low-birth-weight babies: timing changes
For preterm infants under 2,000 grams, timing can change when the birthing parent’s HBsAg test is documented negative. Many hospitals give the hepatitis B vaccine at 1 month of age or at discharge, whichever comes first.
If the birthing parent is HBsAg-positive or the status is unknown, the baby still needs rapid protection: vaccine within 12 hours, with HBIG added based on the same risk rules used for full-term infants. When that early dose is given to a tiny preterm infant, it may be recorded as a “dose 0,” followed by three more doses later, for four total doses on the record.
AAP guidance spells this out in plain terms, including the under-2,000 g timing note, on the AAP hepatitis B vaccine FAQ.
Normal after-effects and when to call
Most babies handle the shot with only mild after-effects: brief fussiness, extra sleep, a sore spot, or a low fever. If you see trouble breathing, swelling of the face, a fever that won’t settle, or a baby who’s hard to wake, call your pediatrician or local urgent service right away.
Mixing brands, combo vaccines, and spacing rules
Switching clinics can mean switching brands. In routine practice, doses from different hepatitis B vaccine manufacturers still count as valid. Clinics still try to stick with one brand when they can, yet a change does not mean the series must restart.
Combination vaccines add another layer. Many infants get a single-antigen hepatitis B shot at birth, then later get a combo product that includes hepatitis B along with other childhood vaccines. Those combos are not used for the birth dose and are not given before 6 weeks of age, so some kids end up with four hepatitis B doses recorded.
CDC’s overview of product types and administration notes this “valid across manufacturers” point and lists the licensed single-antigen and combination options on the CDC hepatitis B vaccine administration page.
If you like reading the fine print, the ENGERIX-B package insert lists the labeled 0.5 mL infant dose and the series timing used in practice.
Spacing that keeps doses valid
Calendar milestones are helpful, yet minimum spacing is what decides whether a dose counts. Your pediatric clinic’s schedule is built around minimum intervals, so a dose isn’t logged “too early.” If your family travels or you change providers, bring the full immunization record so the next clinic can keep spacing clean.
When a dose is missed: catch-up without restarting
Missed appointments happen. The usual fix is simple: give the next needed dose as soon as possible, then finish the series with valid spacing. Time passing does not erase earlier doses.
If the missed dose was the birth dose, clinicians may also double-check the birthing parent’s hepatitis B test results. Birth timing is tied to exposure prevention as well as routine protection.
| Question parents ask | Plain answer | What helps at the visit |
|---|---|---|
| “Is 0.5 mL too much for a newborn?” | 0.5 mL is the standard infant injection volume for licensed HepB vaccines. | Birth record or vaccine card |
| “My baby was early. Do we still do the birth dose?” | Under 2,000 g with HBsAg-negative parent: dose at 1 month or discharge; positive/unknown: dose within 12 hours. | Birth weight and discharge papers |
| “Can we use a combo shot instead?” | Combos start at 6 weeks+. Birth dose is single-antigen. | Current schedule printout |
| “Do brands have to match?” | Doses from different manufacturers still count as valid. | Immunization history |
| “What if the parent’s lab result was missing?” | Hospitals treat it as unknown: vaccine within 12 hours, then act based on the test result. | Prenatal lab records if you have them |
| “When is blood testing done after exposure?” | Testing is done later in infancy after the series, timed to avoid false results from HBIG. | Clinic reminder for the lab visit |
Four questions that keep the visit tight
If you want a quick, clear chat at the visit, these prompts work well:
- “What dates do you want for dose 2 and dose 3?”
- “Which product did we use at birth, and what will we use next?”
- “Do we need HBIG or later blood testing based on the birth record?”
- “If we travel, what’s the earliest date the next dose can be given and still count?”
Practical takeaways
- Infant hepatitis B vaccine doses are commonly 0.5 mL injections in the thigh.
- Most babies follow a 3-dose series starting at birth.
- When the birthing parent is HBsAg-positive or status is unknown, the hospital moves fast and may add HBIG.
- Preterm infants under 2,000 g can have a different timing plan when the birthing parent tested negative.
- Switching brands is usually fine; the clinic documents it so doses count.
References & Sources
- Centers for Disease Control and Prevention (CDC).“Hepatitis B Perinatal Vaccine Information: Vaccine Administration.”Schedules and timing by maternal HBsAg status and infant birth weight, including 12-hour actions and HBIG use.
- Centers for Disease Control and Prevention (CDC).“Hepatitis B Vaccine Administration.”Product overview and administration notes, including dose validity across manufacturers.
- American Academy of Pediatrics (AAP).“Hepatitis B Vaccine Frequently Asked Questions.”Birth dose timing targets, steps for unknown or positive maternal status, and preterm infant timing under 2,000 g.
- U.S. Food and Drug Administration (FDA).“Package Insert – ENGERIX-B.”Licensed infant dose volume and schedule details for Engerix-B.