Oral polio and rotavirus vaccines protect 85-98% of children in high-income countries. Give the same vaccine to a child in parts of sub-SaharanAfrica or Southeast Asia, and that number can drop to 45-57%. It isn't a supplyproblem or a cold-chain problem. The vaccine itself behaves differentlydepending on the gut it lands in.
That puzzle is the subject of a new Forum piece in Cell Host &Microbe, "Improving the vaccine efficacy gap with microbial-derived therapies," co-authored by SPRINGS coordinator Vanessa Harris (AmsterdamInstitute for Global Health and Development, Amsterdam UMC) with Jongchan Kim and Godelieve de Bree.
For over a decade, researchers tried closing the gap with off-the-shelf probiotics like Lactobacillus rhamnosus, on the theory that adding the"right" bacteria would help the vaccine take hold. It mostly didn't work. The authors argue the field has been reading the wrong signal, chasing which species are present rather than what those species actually produce. They point to three more promising angles instead: microbial metabolites that signal directly to immune receptors, bacterial structural components that could act as natural adjuvants, and reducing interference from the enteroviruses already colonizing infants' guts at vaccination age.
The stakes are concrete. Rotavirus is still the leading cause of diarrheal death in children under five, and polio eradication remains stuck in Afghanistan and Pakistan partly for this same reason: a vaccine that quietly performs worse exactly where it's needed most.
This research was conducted independently of SPRINGS; we're sharing it for its relevance to our shared focus on diarrheal disease.
About the project:
SPRINGS is an EU-funded project focused on addressing the impact of climate change on waterborne diarrheal diseases. Diarrheal diseases are currently the third leading cause of death in children under 5 years of age globally. Compounded by global climate projections indicating increased precipitation, flooding, and drought, there is a looming threat to the progress made in reducing diarrheal disease burden. To inform and prioritise effective political responses, SPRINGS is building 4 case studies in Italy, Ghana, Romania, and Tanzania with contrasting vulnerabilities.