Hepatitis B Schedule For Infants | Shot Timing Made Clear

Hepatitis B can become long-term when infection happens early in life, so dose timing gets real attention in newborn care. Here’s the infant schedule, the situations that change what “dose 1” means, and the quick checks that keep the series valid if visits shift.

What The Infant Schedule Is Built To Prevent

A baby can be exposed during birth if the birth parent has hepatitis B, and exposure can also happen later through close household contact or accidental blood exposure. When infection happens in infancy, chronic infection is more likely, so the schedule aims to block that early window.

Hepatitis B Schedule For Infants By Age And Dose

Many infants complete a 3-dose series. Some complete a 4-dose series when combination vaccines are used. The timing rules below are the ones clinics use to keep doses valid.

Dose 1: Birth Or Early Infancy Start

Higher exposure risk: If the birth parent is hepatitis B surface antigen positive (HBsAg positive) or status is unknown at delivery, the baby should receive hepatitis B vaccine soon after birth. HBIG is added when indicated by the perinatal protocol. CDC’s perinatal guidance includes dose tables by birth weight and parent status: Hepatitis B perinatal vaccine administration.

Birth parent tests negative: In the United States, ACIP voted in December 2025 for an individual-based decision process on whether to give a birth dose to infants born to women who test negative; if the birth dose is not used, ACIP suggested starting no earlier than two months of age. CDC’s release is here: ACIP vote on infant hepatitis B birth dosing.

Dose 2: One To Two Months After The Start Dose

Timing: Often at age 1–2 months for babies who received a birth dose. If the first dose starts later, dose 2 is scheduled using the same spacing minimums. Minimum gap: at least 4 weeks after dose 1.

Final Dose: Not Before 24 Weeks Of Age

Timing: Often at age 6–18 months for babies who started at birth. For babies who start later, the last dose still must meet minimum gaps and the minimum age rule.

Minimum gaps: at least 8 weeks after dose 2 and at least 16 weeks after dose 1. The final dose must be given at age 24 weeks (6 months) or older.

Low Birth Weight And Preterm Babies

Birth weight can change dose counting because very small infants may respond less strongly to a day-one dose.

Under 2,000 Grams With A Negative Parent Test

If the birth parent tests negative, a baby under 2,000 grams may receive a dose at birth, yet that dose may not count toward the standard series. A counted dose is then given at age 1 month or at hospital discharge (whichever comes first), which can lead to four total doses logged.

Under 2,000 Grams With A Positive Or Unknown Parent Status

When exposure risk is higher, protection is not delayed. The baby receives vaccine soon after birth and HBIG when indicated, then completes the remaining doses using standard spacing rules.

Combination Vaccines And Why Four Doses Can Be Normal

Some pediatric offices use combination vaccines at 2, 4, and 6 months that include hepatitis B along with other routine infant vaccines. A common pattern is a birth dose followed by three combination doses, giving a four-dose hepatitis B series.

Spacing Rules You Can Check Fast

When a visit is missed or records are split across clinics, the “date math” keeps the series valid:

• Dose 1 → dose 2: at least 4 weeks
• Dose 2 → dose 3: at least 8 weeks
• Dose 1 → dose 3: at least 16 weeks
• Final dose: age 24 weeks (6 months) or older

These minimum intervals are in CDC’s ACIP recommendation report: Prevention of Hepatitis B Virus Infection in the United States.

Table 1 (after ~40%)

Hepatitis B Dose Timing Scenarios

Scenario	Typical Plan	What Changes
Parent HBsAg positive	Vaccine soon after birth + HBIG per protocol; then complete series	Follow-up blood testing is often scheduled later
Parent status unknown at delivery	Vaccine soon after birth while testing is arranged	HBIG use depends on protocol and timing of results
Parent tests negative, birth dose chosen	Start at birth; dose 2 at 1–2 months; final dose at 6–18 months	Final dose must be at age 24 weeks or older
Parent tests negative, no birth dose	Start no earlier than 2 months; finish series using minimum gaps	Clinic maps dates so the last dose meets the 24-week rule
Infant <2,000 g, parent tests negative	Count dose 1 at 1 month or discharge	A birth dose may not count, so four doses can appear
Infant <2,000 g, parent positive or unknown	Vaccine soon after birth; HBIG when indicated; then complete series	Protection starts day one because exposure risk is higher
Using combination vaccines	Birth dose + combination doses later in infancy	Four hepatitis B doses can be routine
Second dose missed	Give the next needed dose when possible	No restart; minimum gaps still apply

What To Do If A Dose Is Late

A late dose is handled by giving the next needed dose when you can. The series is not restarted. The clinic schedules the remaining doses around the minimum gaps and the baby’s age for the final dose.

Follow-Up Testing After Higher-Risk Exposure

When the birth parent is HBsAg positive, clinicians often order post-vaccination blood testing later in infancy to confirm protective antibodies and to rule out infection. Ask your clinic for the target month before you leave the visit.

Table 2 (after ~60%)

Questions To Bring To The Next Visit

Ask This	What You’re Confirming	Write Down
“Which hepatitis B dose number is today?”	Whether it’s dose 1, 2, 3, or an extra combination dose	Dose number + vaccine product name
“What’s the earliest allowed date for the next dose?”	Minimum spacing rules were met	Earliest date + target month
“Does birth weight change counting?”	Whether a day-one dose counts for infants <2,000 g	Birth weight + parent status on record
“Was HBIG given or planned?”	Extra protection steps after higher-risk exposure	Date/time HBIG was given (if applicable)
“Do we need follow-up blood testing?”	Whether testing is planned, and when	Target month + where it will be done

Safety Notes Parents Usually Want

Most babies have no major issues after the shot. Common short-term effects are soreness, brief fussiness, or a mild temperature. Seek urgent medical care right away for trouble breathing, widespread hives, swelling of the face or lips, or a baby who seems unusually hard to wake.

For a plain disease overview, the World Health Organization hepatitis B fact sheet summarizes transmission, long-term risks, and prevention.

Record-Keeping That Saves You Time

Keep one master record with the date and product name for each dose. A photo of the vaccine card works fine. If two clinics are involved, show the photo at every visit so doses aren’t repeated because a record didn’t transfer.

Hepatitis B Schedule For Infants: Quick Checklist

• Birth parent test status noted in the baby’s records
• If parent status was positive or unknown: vaccine soon after birth and HBIG handled per protocol
• If parent tests negative: start timing confirmed (birth dose chosen or start no earlier than 2 months)
• Minimum gaps planned: 4 weeks, 8 weeks, 16 weeks
• Final dose will be at age 24 weeks or older
• Birth weight logged; if under 2,000 g, dose counting confirmed with the clinic