Around 100 trillion bacteria – both good and bad – live in your digestive system, forming the gut microbiota. ‘We know that the microbiome in the gut plays a large role in training and educating our immune system,’ says Dr Macciochi. One of the key ways we can care for the microbes in our gut is by eating a diverse range of dietary fibre from fruit, veg, beans, spices, nuts and seeds. ‘Generally, people in the UK are consuming way less fibre than they should be – aim for 30g per day, and as many different types of plant foods as possible per week,’ says Dr Macciochi.

‘Since the start of the Covid pandemic, we have gathered several studies showing an association between low vitamin D status and infection risk and severity,’ says Dr Macciochi. Vitamin D is synthesised in our skin by sunlight, and in the autumn and winter, when the days are shorter and we are inside more often, everyone should consider a supplement.

Alcohol is not your immune system’s friend. ‘Sadly, there is no way to get around the fact that alcohol isn’t good for our immune systems,’ says Dr Macciochi. ‘There is some evidence that drinking alcohol, especially regular heavy drinking, could interfere with your body’s ability to build immunity in response to infections and vaccines. It is also a gut irritant that can lead to unwanted inflammation in the body, which is a risk factor for lots of chronic diseases.’

What we eat has an important role in keeping us healthy and, in turn, helping to protect against Covid-19. ‘An effective immune response requires an adequate nutritional status of the essential micronutrients (vitamins and minerals including vitamin A, B vitamins, vitamins C, D and E, and the minerals zinc, copper, selenium and iron). A deficiency in any of these could lead to poor immune function,’ says Dr Macciochi. So what should we be eating? Plenty of colourful fruit and veg, for starters. ‘The antioxidants found in fruit and vegetables help reduce inflammation and protect immune cells from destructive free radicals,’ says nutritionist Rob Hobson.

‘When we are stressed for too long, too frequently, cortisol – a key stress hormone – is known to suppress the immune system,’ says Dr Macciochi. GP Philippa Kaye recommends prioritising stress-reduction measures to aid your immunity. ‘Aim for a good night’s sleep. Anything which helps reduce the impact of stress, from exercise to being outside and practising mindfulness, is good news for the immune system.’

Humans weren’t designed to exercise – we were designed to move. And we all need to be moving more and moving in lots of different ways,’ says Dr Macciochi. This means making sure you get at least 30 minutes a day of moderate-level aerobic activity where your heart rate is elevated – a breathy, brisk walk as a minimum, or a run, swim or cycle.

Sleep is our secret weapon for a strong immune system, according to experts. ‘It’s the bedrock of your immunity, as lots of calibration happens when you’re sleeping that allows your immune system to work optimally,’ says Dr Macciochi. ‘When you’re resting – and not really coming into contact with anyone – is when your immune system heals and repairs, ready for the challenges it will inevitably face when you’re up and about the next day.’