A first of its kind human trial based in Adelaide will investigate whether infant immune response to vaccines can be improved by giving probiotics to babies who've been treated with antibiotics in the first week of life.
Globally, infectious diseases are the leading cause of death among children under five and after clean water, vaccination is the best way of protecting infants from these illnesses. However, not all infants respond equally to immunisation, with those treated with antibiotics in early life not producing as many antibodies following vaccination.
Immunologist and program leader at Flinders University and SAHMRI, Professor David Lynn, who's leading the trial with Professor Helen Marshall at the Women's & Children's Hospital, says it's an exciting opportunity for new discovery.
"Our previous preclinical and clinical studies have shown that mice or infants who are given antibiotics shortly after birth typically had weaker vaccine responses, particularly to the PCV13 vaccine, which protects against serious bacterial infections," Prof Lynn said.
"These infants also had lower levels of a beneficial gut bacteria called Bifidobacteria and, in mice, giving a probiotic containing Bifidobacteria helped improve the immune response to the vaccine. We're aiming to find out if that result can be replicated in infants."
To do this, newborns will be randomised to receive either a daily probiotic or placebo for 2 weeks before they have their first immunisations. The probiotic is already used in preterm infants for protection against necrotising enterocolitis (NEC) and has been proven safe for consumption.
Stool and blood samples will be collected to assess how the probiotics impact the infants' microbiome and subsequent vaccine responsiveness.
"This trial will provide rigorous evidence as to whether this simple probiotic intervention can support optimal immune responses to vaccination in early life and we'll also be able to identify the molecular mechanisms governing the differences in vaccine efficacy," Prof Lynn said.
The study may have broader implications for infants whose microbiome may be disrupted for other reasons, such as C-section, formula feeding, being born to mums with a high BMI and those in low-income countries who incur repeated gastrointestinal tract infections.
"Our findings could also be relevant to long-term child health, given prior associations between antibiotic exposure and an increased propensity to develop conditions such as allergies, asthma and obesity," Prof Lynn said.
The trial is being funded through the Bloom Research Program, an initiative of the Women's & Children's Hospital Foundation (WCH Foundation) that supports large-scale, innovative research to improve the health of women and children in South Australia.
Verity Gobbett, Head of Mission at the WCH Foundation says the organisation is proud to be supporting this world-first trial to optimise vaccine response in infants.
"Research such as this is the backbone of modern healthcare and would not be possible without the generous support of the South Australian community," Ms Gobbett said.
Recruitment is expected to begin in early 2025.
