Under the Microscope: Gut Bacteria and Immunity

Aiming to discover how our diet may impact immune response, a New Zealand Covid vaccine study is underway in Rotorua and Christchurch, observing New Zealand’s unique response to the Pfizer-BioNTech Covid-19 vaccine.

The study Ka Mātau, Ka Ora (from knowledge comes wellbeing) is being led by Vaccine Alliance Aotearoa New Zealand and will observe the response of at least 300 New Zealanders over a period of 12 months after their second vaccination.

A small team from the Malaghan Institute of Medical Research in Wellington is involved in the study, including translational immunologists Doctors Alissa Cait and David O'Sullivan.

With research backgrounds in the microbiome – the bacteria that live in our gut – Cait and O'Sullivan will be monitoring the diets of some participants pre-vaccine, to observe if a person's diet may affect their immune response.

A yet to be published study from the Institute has pointed towards a possible link between a high-fibre diet and a greater immune response to the seasonal influenza vaccine.

Dr Alissa Cait

"One of the findings that we had was that people who ate more fibre had a different microbiome, so the bacteria that like to eat fibre were expanded – and they have stronger responses to the influenza vaccine," Cait said.

"What's really interesting about that study was that the effect of fibre was strongest in people that had never been vaccinated before."

Still recruiting for participants in Rotorua and Christchurch, the study will be part of the Government-funded research programme Ka Mātau, Ka Ora, led by Vaccine Alliance Aotearoa New Zealand clinical director Dr Fran Priddy.

As most vaccine studies around the world had taken place in areas with high Covid exposure, the programme would provide a unique snapshot of how New Zealanders responded, with a focus on the Māori and Pacific population.

"We'll have samples from a representative number of New Zealanders, by ethnicity but also by age and gender," explained Priddy.

"But it's not just looking at the immune response to the Pfizer vaccine – in the study, we're basically characterising New Zealand's immune response. The samples will then be stored, and it could be that they're very useful in making sure that the immune responses that New Zealanders have can also protect against new variants, with tests we can do in the lab."

The study will be testing the antibodies in participants' blood prior to vaccination and at six and 12-months post-vaccine. This will enable the researchers to observe for how long a person may be protected. The 300 participants could also elect to take part in the dietary component, which would require them to monitor their food intake for three days prior to the two vaccines.

According to the researchers, a better understanding of the relationship between the microbiome and the immune system could have ground-breaking impacts on health science. It opens the possibility that certain bacteria or foods could help make certain treatments more effective, or just boost overall health.

"The idea that you could improve your immune system by your dietary habits is quite appealing," O'Sullivan said.

"It's not taking a drug from a pharmaceutical company; it's not doing anything particularly onerous and expensive."