Today we shine a light on a study that suggests just how misguided and potentially dangerous new US hepatitis B vaccination guidelines may be for many infants. We also report on an analysis that should ease some concerns for pregnant women taking popular GLP-1 drugs.

A new study hints at the extent to which basing hepatitis B virus vaccination recommendations for infants only on their mother's infection status leaves them vulnerable to the virus from other close contacts.

For decades, the US Centers for Disease Control and Prevention recommended that all infants be vaccinated at birth against HBV. In a controversial new guideline, part of the vaccine overhaul agenda of Health Secretary Robert F. Kennedy Jr., the agency now recommends that only children of mothers with HBV infections or unknown HBV status be vaccinated at birth.

“A child can be exposed to hepatitis B from anyone with an active infection, not just their mother,” study leader Dr. Karen Jacobson of Kaiser Permanente said in a statement.

In the new study of 158,000 children in northern California, researchers identified more than 2,000 whose household included at least one person with active hepatitis B.

In roughly 58% of those, the infected household member was not the child's mother, the researchers reported at the IDWeek meeting in Washington, a large annual gathering of infectious diseases specialists.

HBV, the leading cause of liver cancer worldwide, can be transmitted through contact with body fluids including blood, tears and saliva, and it can live on surfaces for up to a week.

The infection often resolves on its own. But it becomes chronic in more than 90% of infants and in up to 50% of young children who become infected.

“No one knows the status of everyone a child may come into contact with, and vaccinating infants at birth protects against known and unknown potential sources of transmission,” Jacobson said.

Women taking GLP-1 drugs for weight loss and diabetes are advised to stop before becoming pregnant, but new data adds to an earlier report suggesting use in pregnancy might not be a cause for alarm. In June, researchers at the Harvard T.H. Chan School of Public Health had reported on 3,572 pregnancies in women who were taking GLP-1 drugs prior to conception.

The risk for non-live birth was 29.7% with medication continuation into the first trimester, versus 27.1% with non-continuation, a difference that was not deemed statistically significant. In a smaller new study that has not yet undergone peer review, researchers at Cambridge, Massachusetts-based data analytics firm nference analyzed outcomes of 572 pregnancies in women with a prescription for semaglutide within 90 days before the last menstrual period. Of those, 246 of the women continued to use the drug while pregnant.

Semaglutide is sold by Novo Nordisk (NOVOb.CO) in the US as Wegovy for obesity and Ozempic for diabetes.

The researchers also analyzed 101,159 similar pregnancies without GLP-1 use. Similar percentages of pregnancies reached the second trimester, third trimester, and delivery, they found.

Most patients who continued semaglutide use into pregnancy discontinued it after the first trimester. But the drug was prescribed to 54 women in the second trimester and 45 in the third trimester.

Pregnancy complications, such as preeclampsia and gestational diabetes, and rates of preterm birth, stillbirth or neonatal death did not differ between those who continued using the drug and those who stopped taking it.

Mean Apgar scores — a quick health evaluation test performed on a newborn — were also indistinguishable between the semaglutide-continued and the semaglutide-discontinued groups.

Women in the study who continued to use semaglutide had pregnancy-appropriate weight gains, the study also found.

“These observations motivate the need for larger retrospective and prospective studies to rigorously establish the safety of semaglutide exposure during pregnancies,” the researchers concluded.