Early Antibiotic Use May Weaken Vaccine Response in Infants, Study Finds.

New research has uncovered that antibiotics given to infants within their first week of life may have long-lasting effects on their immune response to routine childhood vaccines. The study, published in Nature, indicates that this early antibiotic exposure can diminish antibody responses up to 15 months later—but probiotic supplementation may help reverse the damage.

The first year of life is a critical window for microbiome development. Various environmental exposures, including diet and medical interventions, shape the infant gut microbiota and, in turn, influence immune system function. Antibiotics, often administered to newborns suspected of infection or at risk for sepsis, can significantly disrupt this development. In late-preterm and full-term infants, antibiotic use in the neonatal period ranges between 1.2% and 14%, making it a common practice with potential long-term implications.

Led by immunologist David Lynn of the South Australian Health and Medical Research Institute and Flinders University, along with Helen Marshall from the University of Adelaide, the study followed 191 healthy, full-term infants who were vaginally delivered. Researchers evaluated the infants’ immune responses to a range of vaccines, including the pneumococcal conjugate vaccine (PCV13), meningococcal B vaccine, rotavirus vaccine, and a multivalent vaccine that protects against diphtheria, tetanus, pertussis, hepatitis B, poliomyelitis, and Haemophilus influenzae type b.

The results were striking. Infants who had received antibiotics in their first week of life exhibited significantly lower antibody levels at both seven and 15 months. In contrast, infants whose mothers were given antibiotics during labor (intrapartum) or postnatally did not show a similar reduction in vaccine response.

To understand the underlying mechanisms, the researchers examined the infants' gut microbiota at one week and again at six weeks of age—just before the first scheduled round of vaccinations, except for hepatitis B, which is given at birth. While maternal antibiotic exposure did initially affect the infant microbiome, those differences had largely normalized by six weeks. However, babies who were given antibiotics directly had a marked decrease in Bifidobacteria levels—beneficial microbes often found in probiotics.

This decline in Bifidobacteria was linked to weakened vaccine responses. Though the study could not prove causality in humans, the researchers turned to animal models for further investigation. Using germ-free mice, which naturally exhibit poor immune responses, the team demonstrated that introducing a specific mix of Bifidobacterium strains restored vaccine efficacy. Further experiments with clinically approved probiotics produced similar results, reinforcing the role of gut microbiota in modulating immune function.

Dr. Vanessa Harris, an infectious disease expert at Amsterdam University Medical Center, praised the research but noted that questions remain. While the reduction in antibody titers is significant, she pointed out that without changes in seroconversion rates—how many people develop protective immunity—the clinical relevance is still uncertain. Nevertheless, she acknowledged the potential of probiotics as a practical intervention.

In response to these findings, Lynn’s team has launched a randomized controlled trial to test whether daily probiotic supplementation in antibiotic-exposed infants can improve vaccine responses. Infants will receive either probiotics or a placebo for two weeks leading up to their vaccinations, with researchers analyzing stool and blood samples to track microbiome and immune development.

Lynn is optimistic about the potential public health impact. “The microbiota is something we can target relatively easily,” he said. “Probiotics are affordable, scalable, and could be a low-cost method to boost vaccine effectiveness.”

He concluded with a broader message: “Your microbiome is incredibly important for your health. Protecting it should be a priority from day one.”

Source:https://www.the-scientist.com/early-life-antibiotics-put-vaccine-response-at-risk-72943

This is non-financial/medical advice and made using AI so could be wrong.