Female Newborns More Likely to Miss Vitamin K Prophylaxis, Hepatitis B Birth Dose

Newborn girls in a large Philadelphia health system were more than twice as likely as boys to have their parents decline vitamin K (VK) prophylaxis at birth and modestly more likely to miss the hepatitis B vaccine (HBV), according to a research letter published in JAMA Network Open.¹

Sex-Based Differences in Newborn VK and HBV Vaccine Declines

Intramuscular VK prophylaxis is routinely recommended to prevent vitamin K deficiency bleeding (VKDB), a potentially life-threatening condition that can cause intracranial or gastrointestinal hemorrhage. HBV administration within 24 hours of birth has also been recommended to reduce vertical transmission and subsequent chronic liver disease. Because infants who do not receive VK prophylaxis face an increased bleeding risk, many hospitals do not perform circumcision without it.

To investigate whether newborn sex influences parental decisions regarding these interventions, researchers conducted a retrospective cohort study of 93,163 live births at 3 University of Pennsylvania health system hospitals in Philadelphia between January 2018 and December 2025.

Among these births, 777 infants (8.3 per 1000 births) did not receive intramuscular VK prophylaxis, and 9400 (100.9 per 1000 births) did not receive the HBV birth dose. Notably, 83% of infants whose parents declined VK also went without HBV.

After adjustment for birth hospital, birth year, maternal insurance, race, ethnicity, delivery mode, and gestational age, female newborns had more than double the odds of VK nonreceipt compared with male newborns (adjusted OR [aOR], 2.03; 95% CI, 1.74-2.35; P < .001). The sex gap for HBV was narrower but still significant (aOR, 1.06; 95% CI, 1.01-1.10; P = .02).

Both trends worsened over the study period. VK decline rates among female newborns rose from 9.6 per 1000 births in 2018 to 19.8 per 1000 in 2025, an annual increase of 1.37 per 1000 female births (95% CI, 0.40-2.36; P = .01). Among male newborns, VK decline increased from 4.0 to 10.1 per 1000 births over the same period.

HBV decline rose even more sharply for both sexes, increasing among male newborns from 77.9 per 1000 births in 2018 to 166.3 per 1000 births in 2025 and among female newborns from 86.4 to 173.7 per 1000 births over the same period. By 2025, nearly 1 in 6 newborns in the cohort did not receive the HBV birth dose.

Circumcision Incentives May Help Explain Sex-Based Differences

The authors pointed to circumcision as a likely driver of the VK disparity. Because VK prophylaxis nonreceipt often precludes circumcision at many birth hospitals due to a 6-fold increased risk of bleeding, parents who want their son circumcised may accept VK even if they are otherwise hesitant. Circumcision rates in the cohort ranged from 72% to 77% annually, and no circumcisions were performed among newborns who did not receive VK prophylaxis.

That built-in incentive does not exist for female newborns, which the researchers said may explain why hesitant parents are more likely to decline VK prophylaxis when the infant is a girl. However, no comparable procedural incentive explained the smaller but still significant HBV gap. Although sex disparities in childhood immunization have been documented in low- and middle-income countries, the authors noted that sex-specific differences in HBV uptake are not well described in the literature.

HBV Policy Shift Raises Concerns About Declining Uptake

At the same time, the rise in HBV decline documented in this cohort occurs amid a broader policy shift. In December 2025, the CDC adopted a policy change allowing shared clinical decision-making, rather than a universal recommendation, for the HBV birth dose in infants born to mothers who are HBV-negative, marking the first departure from universal birth-dose guidance in more than 30 years.²

That shift has raised concern among public health experts that moving from a universal recommendation to shared clinical decision-making could reduce coverage over time, jeopardizing a strategy that has contributed to a 99% reduction in pediatric HBV infections.³ The authors of the current study describe the same tension, noting that the policy change conflicts with American Academy of Pediatrics guidance and may reinforce vaccine misinformation at a moment when HBV decline rates are already accelerating.¹

Additional Research Needed to Understand and Address Newborn Care Disparities

The authors concluded by acknowledging several limitations of their study, including that the analysis was conducted within a single health system, potentially limiting generalizability. They also were unable to assess subsequent clinical outcomes, such as VKDB or neonatal hepatitis B infection, beyond the birth hospitalization. As a result, they called for additional research to better understand the observed disparities.

“Further studies should address sex-specific rates of newborn VK prophylaxis and HBV administration, VKDB, and neonatal hepatitis B infection nationally,” the authors wrote. “Innovative strategies are required to reduce disparities in VK prophylaxis and HBV administration and limit life-threatening morbidity among female newborns.”

References

1. Coggins SA, Flannery DD, Mukhopadhyay S, Puopolo KM. Parental decline of newborn vitamin K and hepatitis B vaccine administration by newborn sex. JAMA Netw Open. 2026;9(6):e2618410. doi:10.1001/jamanetworkopen.2026.18410
2. Fact sheet hepatitis B immunization. CDC. December 16, 2025. Accessed July 14, 2026. https://cdc.gov/media/releases/2025/fact-sheet-hepatitis-b-immunization.html
3. Joszt L. Misinformation, access gaps threaten hepatitis B elimination goals. AJMC. June 18, 2026. Accessed July 14, 2026. https://www.ajmc.com/view/misinformation-access-gaps-threaten-hepatitis-b-elimination-goals