A drinkable cholera vaccine containing live bacteria – similar to a probiotic yoghurt drink – could potentially help save thousands of lives in disaster zones and possibly revolutionise how we vaccinate people.
Conventional vaccination can take weeks to be effective because the immune system needs time to respond. But the new approach could provide protection within 24 hours.
While it has yet to be tested on humans, the results in trials on rabbits suggest it has the potential to save lives. “We think this is going to be a very good vaccine, and could induce immunity after a single dose,” says the study’s lead investigator, Professor Matthew Waldor, from the Howard Hughes Medical Institute at Harvard Medical School.
He adds: “We have many different engineering steps to make this an incredibly safe, genetically stable, live vaccine.”
The study found that rabbits infected with the cholera vaccine didn’t get sick a day after being vaccinated despite their immune systems not having had a chance to build up immunity to ward off cholera invaders.
The Harvard team don’t fully understand why it works this fast, but it could be that the vaccine’s bacteria suppress the deadly strains competing for the same resources, or perhaps interfere with their toxin production.
We know that our gut bacteria, the microbiome, is crucial to our health and is an important part of our immune system.
Probiotic yoghurt drinks, which claim to load the body with “good bacteria”, attest to that. The vaccine seems to work similarly. “It’s a living therapeutic that has good effects on health,” says Professor Waldor.
The team are now looking to set up human trials to test its safety, and are considering how to extend the shelf life of this living colony of bacteria to make it useful in disaster zones when it’s needed.
People who are already unwell are particularly hard hit by the infection, which lodges in the small intestine, causing diarrhoea and vomiting, which can lead to fatal dehydration – and spreads the bacteria further.
In Yemen, currently in its third year of civil war, a child dies every 10 minutes from cholera.
A fresh warning of the disease’s resurgence was issued as the rainy season begins and inadequate sewage systems overflow again.
The outbreak’s death toll exceeded one million last year and is on track to be the worst in history.
This new way of vaccinating would be a godsend.