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All of us should take the risk of COVID-19 seriously, as the virus can infect anyone, with serious consequences. However the disease appears to affect some individuals more severely than others.
In the UK the National Health Service (NHS) has split those it deems to be most vulnerable into two groups, those at ‘high risk’ and ‘moderate risk’[1]. These groups are considered vulnerable not because they're more likely to catch the virus. The risk is that if a person in one of these groups catches SARS-CoV-2, they will be more likely to become seriously ill.
As we find out more about the disease, these classifications may be updated, so for the most up to date information, visit the NHS website.
The highest risk groups are people who are immunosuppressed, such as those who have had an organ transplant, those undergoing treatments that inhibit the immune system or who have conditions that inhibit the immune system’s function. People with severe conditions affecting their lungs (severe asthma, cystic fibrosis) are also at high risk.
Pregnant women with serious heart conditions are also considered high risk, as they have a high chance of developing complications if they fall ill with COVID-19.
The moderate risk category is much broader. It includes the elderly (people aged 70 or older), people who are obese, or who are pregnant. People who have certain conditions, like have diabetes, some lung conditions, or problems with their immune systems may also be at risk.
Figure 1. List of moderate risk and high risk groups, as defined by the NHS (as of 14 May 2020) Image Credit: NHS
Why are these people more at risk?
These people are at higher risk because their pre-existing conditions make them more likely to become seriously ill if they're infected with SARS-CoV-2. Let's look at the factors that may affect this.
The immune system is a host defence system, composed of specialised cells and organs which all work together to protect the
body.
Obviously a healthy, fully functioning immune system is important to the body's response to a disease, and therefore many of the high risk groups are those whose immune systems is inhibited in some way.
Individuals with an immune system that is not as effective as expected are often referred to as being immunocompromised or immunosuppressed.
Various factors may impact the immune system’s ability to function. Diseases such as AIDS, or Lupus may cause problems with the immune system. But sometimes immunosuppression is induced by medical professionals to prevent rejection of organ transplants. Certain medications, such as steroids, may also cause immunosuppression as a side effect.
The immune system isn’t the only
factor though. People with problems in their respiratory and cardiac systems may be more likely to get seriously ill. The disease can put strain on these parts of the body,
so if these organs aren’t functioning well, it will more difficult a person to
cope with the symptoms of COVID-19, and the chances of developing serious complications like Acute Respiratory Distress Syndrom (ARDS) will go up.
Older people are more likely to suffer severe symptoms following infection with SARS-CoV-2. The graph below shows case fatality rates by age group. You can see that as age increases, so does risk of death. This trend has been seen in several different countries, as shown on the graph. Older people can have less effective immune systems, and are more likely to have other conditions (sometimes called ‘co-morbidities’). However, even in older groups a good number of people recover from the disease. You can see in the graph, in the 80+ year olds, more than three quarters of people infected with SARS-CoV-2 go on to recover.
Figure 2. Coronavirus: Case Fatality Rates by Age. Data from South Korea, Spain, China, Italy. Image Credit: OurWorldinData.org
There have been a few studies that have shown that while men and women are equally likely to catch SARS-CoV-2, men are more likely to become severely ill, or die from the disease. For example, early data from hospitals in Wuhan, where the outbreak started, showed than men accounted for around 75% of COVID-19 related deaths[3]. There is some debate as to whether this is due to biological, or lifestyle differences between men and women.
Data from the UK shows that more people who are Black, Asian, or from an ethnic minority have a higher risk of death following infection with SARS-CoV-2, even when factors of age, gender, and underlying conditions are accounted for[4]. More research is needed to help us understand why this might be.
Some studies have suggested that these risk factors could impact which countries are most affected by SARS-CoV-2. For example, countries with older populations might suffer more deaths. There is quite a lot of variation between the age structures of different countries: in Nigeria only 0.2% of the population is over 80 years old, whereas in Brazil, 2% of the population is 80 years old or older [5]. It doesn’t sound like a lot, but some researchers think that this could make a difference to the number of people who will fall seriously ill in these countries.
If we know who is most at risk of the disease, these groups can be advised to shield themselves (limit their contact with others). This will help minimise their risk of infection, and help them stay safe.
Guidance sometimes changes, so for up to date government advice on how to support those in your household that may be at risk or if you are in a at risk category use the NHS guidelines available at https://www.nhs.uk/conditions/coronavirus-covid-19/people-at-higher-risk-from-coronavirus/if-you-live-with-someone-at-very-high-risk-from-coronavirus/ .
ARDS- Acute Respiratory Distress Syndrome: A life-threatening condition in which lungs become inflamed, and breathing becomes difficult
Cardiac: Relating to the heart
Immune system: The bodies defence system, it is composed of specialised cells and organs which all work together to protect the body.
Lupus: A long term (chronic) illness, in which the immune system attacks the body, causing inflammation, joint problems and other symptoms.
Respiratory- Related to the respiratory systems (e.g. lungs)
1. LSHTM’s Going Viral podcast: https://www.lshtm.ac.uk/research/research-action/videos-filmed-lectures-and-podcasts
2. Lecture: ‘COVID-19 with Chris Whitty’ Apr 30, 2020. Gresham College https://youtu.be/3BdPKpWbxTg
1. NHS,
Apr 2020, Health A-Z. ‘Who's at higher risk from coronavirus’.Accessed 27 Apr
2020 via: https://www.nhs.uk/conditions/coronavirus-covid-19/people-at-higher-risk-from-coronavirus/whos-at-higher-risk-from-coronavirus/
2. Dana-Farber Cancer Institute. (Mar 2020). ‘What does it mean to be Immunocompromised?’. Accessed Mar2020 via:https://blog.dana-farber.org/insight/2020/03/what-does-it-mean-to-be-immunocompromised/
3. Chen N, Zhou M, Dong X, Qu J, Gong F, Han Y, Qiu Y, Wang J, Liu Y, Wei Y, Yu T. Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study. The Lancet. 2020 Feb 15;395(10223):507-13.
4. Office of National Statistics. Coronavirus (COVID-19) related deaths by ethnic group, England and Wales: 2 March 2020 to 10 April 2020. Accessed: 21/05/20
5. Dowd JB, Andriano L, Brazel DM, Rotondi V, Block P, Ding X, Liu Y, Mills MC. Demographic science aids in understanding the spread and fatality rates of COVID-19. Proceedings of the National Academy of Sciences. 2020 May 5;117(18):9696-8
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