The availability of vaccines has brought hope for the end of the pandemic. Yet COVID deaths and cases are still surging around the world. As we try to immunise the world, the most likely scenario for the next few years is that COVID-19 will be like other infectious diseases, such as flu, that we will need to continuously manage and protect ourselves against.
One of the best ways to do that is by being physically active.
Now, a new systematic review of evidence by me and my colleagues shows that regular physical activity strengthens the human immune system, reduces the risk of falling ill and dying from infectious disease by more than a third and significantly increases the effectiveness of vaccination campaigns. This has important implications for pandemic responses.
In our study, we systematically gathered and reviewed all available evidence relating to the effect of physical activity on the risk of falling ill and dying from infectious diseases such as pneumonia – a frequent cause of death from COVID-19 – on the functioning of the immune system and on the outcome of vaccination. The study was conducted too early in the pandemic to include research into COVID-19 itself, but the findings are highly relevant to the current pandemic response.
We found consistent and compelling evidence across six studies involving more than a half million participants that meeting the recommended guidelines for physical activity – 30 minutes of activity, five days a week – reduces the risk of falling ill and dying of infectious diseases by 37%.
This adds to the results of another new study conducted in the United States specifically on COVID-19. The effect is at least as strong if not more so than the effect reported for other risk factors of COVID-19 such as age or having a pre-existing condition such as diabetes.
We also found reliable evidence that regular physical activity strengthens the human immune system. Across 35 independent randomised controlled trials – the gold standard for scientific evidence – regular physical activity resulted in elevated levels of the antibody immunoglobulin IgA. This antibody coats the mucosal membrane of our lungs and other parts of our body where viruses and bacteria can enter.
Regular physical activity also increases the number of CD4+ T cells, which are responsible for alerting the immune system of an attack and regulate its response.
Finally, in the randomised controlled trials we studied, vaccines appear more effective if they are administered after a programme of physical activity. A person who is active is 50% more likely to have a higher antibody count after the vaccine than somebody who is not active.
This can be a cost-effective and easy way of boosting vaccination campaigns. Considering the difficulties in supply chains, this could be a wise move to make every dose count.
How physical activity wards off disease
There are three mechanisms that make physical activity an effective medicine against infectious diseases.
First, it protects against risk factors of severe and fatal infection. Physically active people are less likely to develop obesity, diabetes, respiratory and cardiovascular conditions. Epidemiological studies have shown that COVID-19 and other respiratory infectious diseases are more severe for people who have these conditions.
Physical activity also reduces stress and chronic inflammation, in turn reducing the likelihood of adverse and fatal infections. Most COVID-19 and pneumonia fatalities have been as a result of uncontrolled inflammatory response.
Physical activity is undeniably an important way to make populations less vulnerable to infectious diseases and future epidemics and pandemics. It should be used more urgently and effectively in fighting the current COVID-19 outbreak, but also as a long term investment to prevent the devastating social and economic impacts this pandemic has had on society.
Governments encouraged people to stay active early in the pandemic to cope with lockdown measures. There was a surge of interest in exercise immediately following lockdown in most communities. Unfortunately, this has not translated into positive change in activity levels.
Instead, an apparent decrease in physical activity levels has been seen globally in the past year. This is a dangerous trend that could make the population more vulnerable to infectious and chronic diseases in the short term. Left unchecked, it will also leave a damaging long-term legacy and increase the burden of disease and its associated social and economic cost.