Norovirus vaccine trial launches

Interview with Patrick Moore

A vaccine trial - called the Nova-301 trial - has just launched across the world to find out if we can protect people against norovirus. The stomach bug is rife at the moment across the Northern hemisphere. It causes millions of cases of diarrhoea and vomiting each year, and it spreads like wildfire, partly because each infected person has enough virus leaving their body, upwards and downwards to potentially infect the entire world population. And it doesn’t only hit hospital wards and schools - but also national growth. So, how might a vaccine help? Well it’s being made by Moderna, one of the companies behind the Covid jabs used during the pandemic, and it’s based on the same sort of technology: the mRNA message coding for parts of the virus that the immune system can react to is injected and hopefully primes a protective response. Dorset GP Dr Patrick Moore is the chief investigator on the study…

Patrick - Norovirus is also known as the winter vomiting bug. It tends to cause severe nausea and vomiting with diarrhoea that lasts about one to three days.

Chris - And how much does this cost the economy, do we think?

Patrick -
If you look at the effect on the NHS, so how much does it cost to give patients who have norovirus the treatment, it's about a hundred million pounds per year. But when you take into account other financial factors, such as lost earnings for example, it's probably estimated around 300 million pounds a year.

Chris - Goodness, it's a lot isn't it? There must be millions of cases to reach that sort of figure. It must be running into the millions of cases per year.

Patrick - Globally, we have about 685 million cases a year. In the UK it's about 4 million.

Chris - There's certainly big numbers. And at the moment there is no way to prevent them apart from infection control and keeping out of the way of people who've got it, presumably?

Patrick - That's correct. So the only treatment is actually supportive. So it's oral rehydration or intravenous rehydration, which is usually a hospital admission.

Chris - And how easy is it to catch?

Patrick - This is one of the most transmissible viruses that we have, actually. It is extremely easy to catch it. So it's either aerosol, someone's vomiting in the same room, or it's what they call faecal oral.

Chris - What's the strategy that's being taken then to try to prevent people catching it?

Patrick - So we're looking to see if we can vaccinate against this virus. It's quite a difficult virus to vaccinate against because there are so many different genotypes and genogroups. So norovirus is actually a family of viruses. And actually if you look at all of the viruses that are out there, there's 10 genotypes. And in those genotypes there's 49 genogroups.

Chris - So presumably you could catch one and make it a response to that, but then if you caught a related one a bit later on, you would have fewer defences against that and you become ill again. So it's pretty tricky to stop it.

Patrick - Yeah, correct. I mean, not all of those viruses circulate within humans, but there are certain viruses that are more popular in humans, and that's what the vaccine is trying to protect against. So they've taken three of those viruses and they've produced a vaccine to protect against those three common viruses that we have in humans.

Chris - And what's the nature of the trial you're doing? How does it run? Who's the Guinea pig effectively and what's the nature of the vaccine?

Patrick - So this is what they call a Phase 3 trial. We have been through the earlier phases. The Phase 1 and the Phase 2 trials have shown a good safety profile and also that the bodies produce a good antibody response to the vaccine. We're looking to recruit in the UK about 2,500 participants from about 27 NHS sites. It's quite a large trial and it's what they call a double blind randomised control trial, which basically means that nobody knows whether you get the active vaccine or whether you get a sort of a saline vaccine. And what we do then is we then measure the efficacy, so how well the vaccine works.

Chris - Presumably you'll be looking at the people you vaccinate to see what the rates of natural infection are then and seeing if you get fewer of those infections in the people who've got the real deal versus the saline placebo. And if you do, then you can argue it seems to be protecting people.

Patrick - That's exactly how it works. Yeah. And obviously we'll be measuring and monitoring the safety profile of the vaccine as well and whether it's tolerated well and ensure that our participants are safe.

Chris - How long are you going to follow the participants up for?

Patrick - Trials are running for two years. We vaccinate our participants. We then do a two year follow up. So in that time we'll look to see how well the antibody response is there for, but also we'll then be measuring whether there are any cases of gastroenteritis which are caused by Norovirus. And that will give us our efficacy endpoint.

Chris - And going forward, let's assume that you do get the result we're all hoping you do and this does work. How is it going to be used?

Patrick - That's a decision for the regulatory authorities to decide how it's being used. But certainly from a medical GP perspective, we do have a significant burden in hospitals and care homes, not just with the residents but also the staff as well. They have a lot of time off work and a lot of pressure on the NHS over the winter months. Ultimately, I see that as the main benefit.

Chris - Would it join the ranks of the annual flu and possibly Covid vaccines that we give people? Given that this does seem to have a seasonality to it, it becomes more common in winter and less so the rest of the year. So it would make sense to kind of front load the system or anticipate when someone's going to come into hospital, give them a dose of this before they come in with enough lead time, obviously, so that they're less likely to succumb when they're in.

Patrick - Yeah, I mean that's a good idea. But I suppose there's two things to sort of understand first, which we'll be looking at in the trial. So the first thing is how long does immunity last? We don't know that yet. And it could be that it lasts for a year. It could be that it lasts longer. And then the second thing is how much is the virus changing? How is it evolving? We don't know whether that vaccine will be effective in subsequent years. So again, that is something that we need to be looking at with this study.