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NCT Number: NCT07189390

The Bloom Infant Probiotic (BIP) Study

The goal of this clinical trial is to investigate whether administering a probiotic (Infloran®) to infants who received antibiotics in the first 28 days of life can restore or enhance their immune response to routine vaccines.

Antibiotic use in the first weeks of life can lower the levels of beneficial gut bacteria, such as bifidobacteria, which play a key role in immune function. As a result, infants treated with antibiotics may produce fewer antibodies after routine vaccinations, leaving them less protected against infections.

The main questions this study aims to answer are:

* Does treatment with the probiotic Infloran® improve the geometric mean concentrations (GMCs) of anticapsular antibodies against at least 11 serotypes included in the pneumococcal conjugate vaccine (PCV20) in serum samples collected at 6 months of age compared with placebo in infants treated with antibiotics in the neonatal period? * Does treatment with the probiotic Infloran® improve the GMCs for the pneumococcal conjugate vaccine (PCV20) at 12 months of age compared with placebo in infants treated with antibiotics in the neonatal period? * Does treatment with the probiotic Infloran® improve the GMCs of other routine childhood vaccines at 6 and 12 months of age compared with placebo in infants treated with antibiotics in the neonatal period? * Does treatment with the probiotic Infloran® increase the proportion of infants achieving seroprotective antibody levels for pneumococcal antigens compared to placebo in infants treated with antibiotics in the neonatal period? * What are the differences in antigen specific T cell responses, flow cytometry, blood transcriptomics, and gut microbiota composition in the probiotic (Infloran®) vs placebo groups in infants treated with antibiotics in the neonatal period?

Researchers will compare infants who receive Infloran® (a probiotic containing Bifidobacterium bifidum and Lactobacillus acidphilus) with those who receive a placebo (which contains the same excipients as Infloran® but does not contain any bacterial strains).

Participants will:

* Be randomly assigned to receive either a 14-day course of probiotic Infloran® or a placebo. * Provide blood samples (3-5 mL) at 6 weeks, 6.5 weeks (optional blood-draw for exploratory endpoint), 6 months and 12 months of age. * Provide stool samples at four timepoints: prior to starting the intervention (probiotic/placebo), on day 7, on day 14 after completion of the study supplement, and prior to their first vaccination at 6 weeks of age. * Receive routine vaccinations at 6 weeks, 4 months and 6 months in line with the National Immunisation Program * Complete surveys to collect information regarding probiotic/placebo administration and vaccination related side effects

This study aims to recruit 360 infants to assess whether this probiotic treatment following antibiotic exposure improves the immunogenicity of vaccinations. The information from this study will improve our understanding of how probiotic intervention can support optimal immune responses to vaccination in early life. The findings could potentially influence public health strategies, offering a new way to support optimal vaccine responses in antibiotic-treated infants.

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Key information

Conditions

Infant, Newborn Antibiotic Treatment Immunisation Immunity Microbiome Dysbiosis

Age range

Up to 28 day

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 2

Primary location

Flinders Medical Centre, Adelaide, South Australia, Australia

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Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Infants administered antibiotics in the first 28 days of life. Infants must have documented direct antibiotic exposure - defined as having received at least 36 hours of antibiotic treatment in the neonatal period (the first 28 days after birth).
  • Gestational age ≥ 35 weeks.
  • Birth weight ≥ 2500g.
  • Mother aged at least 18 years and able and willing to provide written informed consent for themselves and their infant.
  • Parent/guardian agrees to not give any other probiotics to their infant prior to vaccination at 6 weeks, including any formula that contains probiotics.
  • Infant planning to receive all nationally approved vaccines during next 6 months.

Exclusion criteria

  • Significant medical condition in either the mother or infant that, in the opinion of a medical investigator, may interfere with the study.
  • Infant had confirmed sepsis or other serious infection in the neonatal period.
  • Infants with known congenital diseases or who are immunocompromised or considered medically at risk (MAR).
  • Infant participating in another interventional trial during the trial period.

Treatment and study plan

Probiotic

Drug

Probiotic capsule contents will be dissolved in a small amount of breast milk, formula or sterile water (drinking water boiled, then cooled) and administered by the infant's parent/guardian to infants as an oral bolus dose. Probiotic Infloran® Hard capsules (Bifidobacterium bifidum & Lactobacillus acidophilus) are a listed medicine on the Australian Register of Therapeutic Goods (ARTG). Infloran® has been previously used in infants including pre-term infants for other indications including supporting healthy digestion or improving digestive system flora. Infloran® is manufactured by Laboratorio Farmaceutico SIT S.r.l., Via Cavour 70 - 27035 Mede (PV) Italy.

Other names: Infloran®

Matching Placebo

Drug

Placebo contains the same excipients as Infloran, it is also made from the same capsule, but it does not contain any bacterial strains. Placebo capsule contents will be dissolved in a small amount of breast milk, formula or sterile water (drinking water boiled, then cooled) and administered by the infant's parent/guardian to infants as an oral bolus dose. The placebo is manufactured by Syntro Health, 558-562 Swan St, Richmond, VIC 3121.

Primary outcomes

  1. The Geometric Mean Concentrations (GMCs) of anticapsular antibodies against at least 11 serotypes included in the pneumococcal conjugate vaccine (PCV20) in serum collected at 6 months in the probiotics vs placebo group.

    Time frame: 6 months

Secondary outcomes

  1. The GMCs for at least 11 serotypes included in pneumococcal conjugate vaccine (PCV20) as measured by serum assay at 12 months in the probiotic vs. placebo group.

    Time frame: 12 months

  2. The GMCs for other vaccine antigens (e.g. diphtheria, tetanus and pertussis toxoids, Haemophilus influenzae type b polyribosylribitol phosphate, Hepatitis B surface antigen) as measured by serum assays at 6 and 12 months in both arms.

    Time frame: 12 months

  3. Proportion of infants achieving seroprotective antibody levels (i.e. seroprotection) for pneumococcal antigens.

    Time frame: 12 months

Other outcomes

  1. Activation-induced markers (AIM) assays will be performed to assess antigen-specific CD4 and CD8 T cell responses in probiotic vs. placebo groups.

    Time frame: 12 months

  2. Flow cytometry analysis of blood samples to compare immune cell frequencies and activation marker expression in probiotic vs. placebo groups.

    Time frame: 12 months

  3. Blood transcriptomics using RNA (ribonucleic acid) sequencing to measure gene expression responses to immunisation (i.e. which genes are turned on or off in blood) in probiotic vs. placebo groups.

    Time frame: Before and after the participants' 6-week immunisations

  4. Assessment of bacterial load (qPCR (quantitative Polymerase Chain Reaction) assay) and microbial composition of the stool microbiota using metagenomics (microbial DNA sequencing) in probiotic vs. placebo groups.

    Time frame: 2 months

  5. Correlative analysis of metagenomic, transcriptomic, and immunological datasets.

    Time frame: 12 months

  6. Assessment of whether probiotic supplementation influences the incidence and severity of respiratory infections during the first 12 months of life.

    Time frame: 12 months

Study contacts

Contact information is provided by the study sponsor or research team.

David Lynn

CONTACT

[email protected]

+61 881 284 053

Elisabeth Reid

CONTACT

[email protected]

+61 881 284 247

Sponsors and collaborators

Lead sponsor

South Australian Health and Medical Research Institute

Other

Collaborators

  • Flinders Medical Center
  • Flinders University
  • The University of Western Australia
  • Women's & Children's Hospital Foundation
  • Women's and Children's Hospital, Adelaide

Registry information

Official study title

A Randomised Controlled Trial to Assess if a Probiotic Intervention Leads to Enhanced Immune Responses to Vaccination in Antibiotic-treated Infants (Bloom Infant Probiotic (BIP) Study)

Acronym: BIP

Important dates

Study start
2026
Primary completion
2029
Study completion
2029
First posted
Sep 24, 2025
Registry last updated
May 28, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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