A New Zealand Covid vaccine study aims to discover how our diet may impact immune response.
A clinical study is underway in Rotorua and Christchurch, observing New Zealand's unique response to the Pfizer-BioNTech Covid-19 vaccine.
Led by Vaccine Alliance Aotearoa New Zealand, the study Ka Mātau, Ka Ora (from knowledge comes wellbeing), 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.
Both with a research background 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.
"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."
"So when the Covid vaccine started being rolled out, we thought what an interesting study population of people who had never been vaccinated for Covid."
Multiple studies around the world had also shown the immune responses of mice could be altered by short-chain fatty acids, produced by the bacteria that eat fibre.
"In animal studies you can give the short-chain fatty acids without the fibre and still see the effects," O'Sullivan said.
"At least in animals it looks like the short-term fatty acids are the thing that enhances this immune response."
But as the initial influenza study had not been peer reviewed, the researchers would be observing participants' diet with an open mind, looking for any dietary components that could have an impact on immune response.
"The idea is to see between those three thing – the immune response, the microbiome, and food – and how all those things play together," O'Sullivan said.
"It's a very complex system obviously and what we eat is so complex and diverse – there's so many different nutrients in it.
"We're not going to be able to say from the study, this particular nutrient is the key, but we might be able to see trends that push us to explore something further."
O'Sullivan said it was also important to note increased immune response did not necessarily correlate to increased protection.
"We look at antibody responses – when you're vaccinated you produce antibodies that specifically bind to the virus," he said.
"But it's not necessarily that if you have 10 times the amount of antibodies you will have 10 times the amount of protection."
"There may be a threshold that if you reach it, you are protected anyway."
The relationship between gut bacteria and overall wellbeing has gained traction in science and the media over the past decade.
"It's becoming more and more evident that changes in the microbiota that live in your gut, and the type of population that hang out in your gut can have very pronounced effects on all sorts of things," O'Sullivan said.
"It often appears that diversity is good, so the greater diversity and the less of a monoculture you have, the more stable your microbiome is, and the more resilient to things that might disrupt that balance."
Cait said around 70 per cent of the body's immune cells are in the gut, with the intestines the "interface between your environment and the rest of your body."
"So it makes sense these immune cells would be evolved to be sensitive to signals coming from your diet," she said.
The study would be part of the Government-funded research programme Ka Mātau, Ka Ora, led by Vaccine Alliance Aotearoa New Zealand clinical director Dr Fran Priddy, which was still recruiting for participants in Rotorua and Christchurch.
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 amount of New Zealanders, by ethnicity but also by age and gender," Priddy said.
"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 would be testing the antibodies in participants' blood prior to vaccination, and at six and 12-months post-vaccine. This would 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.
O'Sullivan said New Zealand was in a unique position to study a population that was "immuno-naïve" - that had largely not been exposed to Covid-19.
"We're lucky that we can use the New Zealand population to explore these things whereas in the rest of the world it would be difficult to investigate in this controlled way."
Better understanding the relationship between the microbiome and the immune system could have groundbreaking impacts on health science, said the researchers.
It opens up 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."
And the suggestion – however loose at this stage – that fibre and a diverse source of nutrients were beneficial to the immune system also did not stray far from general health advice.
"I like the idea that all the health advice is fairly consistent," Cait said.
"The best thing you can do for having an all-round healthy life are things like eating good foods … in some ways it's boring, but in other ways it's comforting."