One Small Shot on the First Day: What New Research Tells Families About the Hepatitis B Birth Dose

Four studies from Africa, Australia, Korea and the United States on how the birth dose protects babies, whether it is safe for the tiniest preemies, what else helps, and what happens when it is skipped

The hepatitis B birth dose is a vaccine given in a baby's first day of life to stop a liver virus passing from mother to child. Four studies published in 2025 and 2026 show that babies who get it on time are infected far less often, that it appears safe even for babies born very early, that some mothers also need medicine during pregnancy, and that babies who miss it are much less likely to finish their vaccine series.

Why a vaccine on the very first day matters

Hepatitis B is a virus that infects the liver. A mother who carries it can pass it to her baby around the time of birth, something doctors call mother-to-child transmission. Babies infected this way rarely clear the virus: more than 90 out of every 100 become lifelong carriers [1]. The birth dose is the first shot of a three-shot series. Giving it in the first hours is like locking the front door before a storm arrives, rather than after the wind is already inside.

Four studies, four pieces of one puzzle

Between March 2025 and April 2026, four research teams each tackled one question about this small shot, and each answer builds on the last. Riches and colleagues combined results from many African studies to estimate how much infection the birth dose could prevent, and why it is not enough on its own [2]. Morgan and colleagues in Australia checked whether the dose is safe for babies born extremely early [3]. Ki and colleagues in Korea looked at the babies who still became infected even though they received every recommended protection [1]. And Williams and colleagues in the United States asked what happens to the rest of a child's hepatitis B vaccines when the birth dose is skipped [4].

These questions matter now. According to the US study's authors, a December 2025 federal announcement in the United States changed advice for babies whose mothers test negative for hepatitis B, making the birth dose a matter of "individual-based decision-making" [4]. In the same month, the Viral Hepatitis Prevention Board (VHPB), a group that published a statement on this question, urged that every newborn keep receiving the dose within 24 hours [5].

How we got here

The story begins in the early 1980s in Taipei, Taiwan. Researchers ran a randomised trial, meaning babies were assigned to treatments by chance, like a coin toss, so that the groups could be fairly compared. The babies' mothers carried hepatitis B. Giving both the vaccine and hepatitis B immune globulin (HBIG), an injection of ready-made protective antibodies, prevented about 94% of the infections that would otherwise have happened; only 6 in 100 protected babies became long-term carriers, compared with 88 in 100 babies without protection [6].

That success shaped the modern approach. The World Health Organization (WHO) has recommended hepatitis B vaccine for all infants since 1992 [2]. In the United States, national advisers recommend testing every pregnant woman, giving babies of mothers with the virus both vaccine and HBIG within 12 hours, and vaccinating all other babies within 24 hours [7]. Yet questions remained. In Africa, birth-dose use lagged: by 2022 only about a third of countries offered it, reaching fewer than 1 in 5 newborns [2], and an earlier review could not show clearly that it beat starting vaccines at six weeks [8]. A study at Tokombéré District Hospital in Cameroon, known as ANRS 12303, found that timing mattered, and that some babies were still infected when their mothers had very high amounts of virus in the blood [9]. A trial in China had shown that an antiviral medicine called tenofovir, taken by such mothers late in pregnancy, lowered that risk [10].

What the African study found: sooner is better

About 6 in every 100 pregnant women attending clinics in the WHO African region carry hepatitis B [2]. When the researchers pooled studies that tested babies at 6 to 12 months of age, about 4 in 100 babies vaccinated within 24 hours became infected, compared with about 7 in 100 who only started vaccines later in infancy and about 16 in 100 who were never vaccinated. A dose given a few days late did not clearly help more than waiting for the later shots [2], matching the Cameroon findings [9]. The team estimated that about 172,000 African babies caught hepatitis B from their mothers in 2022, and that reaching vaccine targets plus offering tenofovir to the mothers at highest risk could prevent about 86% of those infections [2].

Is it safe for babies born very early?

Some doctors worried that vaccinating the very smallest premature babies on day one might worsen bronchopulmonary dysplasia (BPD), a long-lasting lung condition of prematurity in which the lungs have trouble growing and the baby needs breathing support for many weeks. The Australian team used linked health records for 818 babies born before 29 weeks of pregnancy (more than two months early) in five neonatal intensive care units in Melbourne, Australia, between 2017 and 2020 [3]. About 51 in 100 vaccinated babies developed BPD, compared with about 62 in 100 unvaccinated babies, and deaths in the first three months were similar (about 2 to 3 in 100 in both groups). In short, the birth dose did not make BPD more likely. The researchers caution that this was not a randomised trial: sicker babies may have been less likely to be vaccinated, so the study cannot show that the vaccine protects the lungs [3]. Families interested in BPD treatment can read our article on steroids after birth for BPD.

What still gets through, and how mothers can help

Korea's national Perinatal Hepatitis B Prevention Program (PHBPP) gives every baby of a mother with hepatitis B both the vaccine and HBIG within 12 hours, then checks the baby's blood around the first birthday. Across 154,478 mother–baby pairs over 20 years, about 2 in 100 babies were still infected [1]. The risk was highest when the mother had a positive hepatitis B e antigen (HBeAg) test, a blood marker showing that the virus is very active. When the mother was HBeAg-positive and not taking medicine, about 6 in 100 babies were infected; when she took antiviral medicine (tablets that slow the virus down), it was about 1 in 100. Medicine started earlier in pregnancy and continued after delivery was linked to the lowest risk. As more mothers took these medicines, infections fell from about 3.6 in 100 babies in the early 2000s to 1.3 in 100 recently [1].

Breastfeeding was not linked to more infections, and the American College of Obstetricians and Gynecologists (ACOG), which advises obstetricians in the United States, encourages mothers with hepatitis B to breastfeed [11]. Babies born by caesarean section had slightly fewer infections in Korea, but this kind of study cannot prove the operation was the reason. ACOG does not recommend a caesarean just to prevent hepatitis B [11], while the European Association for the Study of the Liver (EASL) conditionally suggests it for some mothers with very active virus and high virus levels who are not taking medicine [12]. That decision belongs with your obstetric team.

What happens when the first dose is skipped

The US team looked at 1,119,709 children in nine health systems that share records through the Vaccine Safety Datalink. Among children who got the birth dose, about 98 in 100 finished all three hepatitis B shots by 18 months [4]. Among those who skipped it, about 73 in 100 born in 2014 finished, falling to about 55 in 100 born in early 2023, and the share who received no hepatitis B shots at all nearly doubled [4]. Think of the birth dose as the first step of a staircase: families who take it almost always reach the top. The study cannot prove that skipping the first step causes the rest to be missed; families who decline it may have wider worries about vaccines [4].

What this means for your family

If you are pregnant, ask for your hepatitis B test result and what it means. If you carry the virus, ask about your viral load (the amount of virus in your blood) and whether antiviral medicine is right for you, ideally well before delivery. Ask your baby's team when the birth dose will be given, including if your baby is born early. If you carry hepatitis B, your baby will also need a blood test after the vaccine series to confirm protection [7]. It is always fine to ask questions; paediatricians have guidance on answering families' vaccine questions openly [13]. A related question about another virus is covered in our article on early hepatitis C testing for babies.

What researchers are working on next

In Africa, researchers want to make birth doses routinely available within 24 hours and to pair them with testing and medicine for mothers [2]. For premature babies, a large randomised trial would give the most certain answer on safety [3]. Korean researchers recommend adding viral-load testing in pregnancy to decide who needs medicine [1], and US researchers suggest tracking declined birth doses to find children who may need extra help finishing their vaccines [4].

The bottom line

Read together, these four studies tell one reassuring story. A shot on the first day is linked to far fewer infections [2], appears safe even for the smallest babies [3], works best alongside medicine for mothers with very active virus [1], and is usually the start of a completed series [4]. For most families, it is a small, early step in protecting a child from hepatitis B.

References

  1. Ki M, Kim BW, Baik D, Kim JH. Factors associated with hepatitis B mother-to-child transmission in a national prevention program. Clin Mol Hepatol. 2025;31(4):1298–1315. doi:10.3350/cmh.2025.0214 ↩
  2. Riches N, Henrion MYR, MacPherson P, et al. Vertical transmission of hepatitis B virus in the WHO African region: a systematic review and meta-analysis. Lancet Glob Health. 2025;13(3):e447–e458. doi:10.1016/S2214-109X(24)00506-000506-0) ↩
  3. Morgan HJ, Nold MF, Sepulveda Kattan G, et al. Hepatitis B vaccination of preterm infants and risk of bronchopulmonary dysplasia: a cohort study, Australia. Bull World Health Organ. 2025;103(3):187–193. doi:10.2471/BLT.24.291683 ↩
  4. Williams JTB, Cruz H, Stein A, et al. Hepatitis B vaccine series completion by 18 months in infants without a birth dose. JAMA Netw Open. 2026;9(4):e269962. doi:10.1001/jamanetworkopen.2026.9962 ↩
  5. Van Damme P, Hendrickx G, Jindal S, et al. The Viral Hepatitis Prevention Board (VHPB) supports the continued recommendation for universal hepatitis B vaccination of all newborns within 24 hours of birth. Hum Vaccin Immunother. 2025;21(1):2600657. doi:10.1080/21645515.2025.2600657 ↩
  6. Beasley RP, Hwang LY, Lee GC, et al. Prevention of perinatally transmitted hepatitis B virus infections with hepatitis B immune globulin and hepatitis B vaccine. Lancet. 1983;2(8359):1099–1102. doi:10.1016/S0140-6736(83)90624-490624-4) ↩
  7. Schillie S, Vellozzi C, Reingold A, et al. Prevention of hepatitis B virus infection in the United States: recommendations of the Advisory Committee on Immunization Practices. MMWR Recomm Rep. 2018;67(1):1–31. doi:10.15585/mmwr.rr6701a1 ↩
  8. Keane E, Funk AL, Shimakawa Y. Systematic review with meta-analysis: the risk of mother-to-child transmission of hepatitis B virus infection in sub-Saharan Africa. Aliment Pharmacol Ther. 2016;44(10):1005–1017. doi:10.1111/apt.13795 ↩
  9. Shimakawa Y, Veillon P, Birguel J, et al. Residual risk of mother-to-child transmission of hepatitis B virus infection despite timely birth-dose vaccination in Cameroon (ANRS 12303): a single-centre, longitudinal observational study. Lancet Glob Health. 2022;10(4):e521–e529. doi:10.1016/S2214-109X(22)00026-200026-2) ↩
  10. Pan CQ, Duan Z, Dai E, et al. Tenofovir to prevent hepatitis B transmission in mothers with high viral load. N Engl J Med. 2016;374(24):2324–2334. doi:10.1056/NEJMoa1508660 ↩
  11. ACOG Committee on Clinical Practice Guidelines–Obstetrics. Viral hepatitis in pregnancy: ACOG Clinical Practice Guideline No. 6. Obstet Gynecol. 2023;142(3):745–759. doi:10.1097/AOG.0000000000005300 ↩
  12. European Association for the Study of the Liver. EASL Clinical Practice Guidelines on the management of liver diseases in pregnancy. J Hepatol. 2023;79(3):768–828. doi:10.1016/j.jhep.2023.03.006 ↩
  13. O'Leary ST, Opel DJ, Cataldi JR, et al. Strategies for improving vaccine communication and uptake. Pediatrics. 2024;153(3):e2023065483. doi:10.1542/peds.2023-065483 ↩