A new study published Monday in JAMA Pediatrics suggests that a recent change to Centers for Disease Control and Prevention vaccine recommendations could result in hundreds of additional hepatitis B infections and increased healthcare costs.

The CDC in December approved changes to its longstanding practice of recommending that infants receive a dose of the hepatitis B vaccine within 24 hours of birth. The agency moved away from this specific timing recommendation as part of broader updates to its vaccination guidelines.

Researchers analyzing the policy change predict it will lead to worse health outcomes and millions of dollars in additional healthcare costs. The study authors modeled potential infection rates under the new guidelines compared to the previous 24-hour recommendation.

Hepatitis B is a viral infection that attacks the liver and can cause both acute and chronic disease. When transmitted from mother to child during birth, the infection can lead to serious long-term health complications including liver damage and cancer. Early vaccination has been considered crucial for preventing mother-to-child transmission.

The research comes as public health officials continue to evaluate vaccination policies and their real-world impacts on disease prevention and healthcare systems.