"Heel-prick samples appear to be a practical and reliable way of measuring these antibodies," says May Murra, a postdoctoral researcher at the Department of Biomedicine at Aarhus University. "A major advantage is that the samples are already collected routinely, and the material is easier to collect, store and transport than standard blood samples."

Why it matters for vaccines

GBS can cause serious infections in newborns, which is why researchers are searching for better ways to protect infants. One leading approach is to vaccinate the mother during pregnancy so her immune system produces antibodies against the bacterium. Those antibodies then transfer to the baby before birth.

That strategy only works if scientists understand how effectively mothers pass antibodies on. "To improve our ability to protect newborns against serious GBS infections, we need to know how effectively mothers can transfer antibodies to their babies before birth," Murra explains. "We can now gain that knowledge, having shown that the heel-prick samples already collected from newborns can be used to measure antibody levels."

In the short term, the findings matter most to researchers and vaccine developers working on GBS vaccines for pregnant women. The Aarhus team has already begun investigating the relationship between the amount of GBS antibodies in a baby and the risk of developing an infection. Their goal is to determine what antibody level is needed to protect a newborn.

If researchers can identify an antibody level associated with protection, that threshold could potentially serve as a benchmark for assessing how well future vaccines work.

"In the longer term, we hope this knowledge can help pave the way for a vaccine for pregnant women that can protect newborns against serious GBS infections," says Murra. "First, however, we need to learn more about what level of antibodies actually protects the baby."

Important caveats

The study is a small proof-of-concept investigation. In other words, the researchers set out primarily to test whether the method works in principle, not to draw definitive conclusions about protection or vaccine effectiveness at a population level. The team is now working to expand the research using a larger set of blood samples drawn from different populations and countries.

Until those larger studies are complete, the results should be treated as a promising early step rather than a finished clinical tool.

Publication details

The study, titled "Assessment of dried blood spot and umbilical cord blood samples for the quantification of maternally transferred IgG against the group B streptococcal alpha-like surface proteins in neonates at Kolding Hospital, Denmark: a proof-of-concept, cross-sectional study," appears in The Lancet Microbe (2026), DOI: 10.1016/j.lanmic.2026.101409.