What are the underlying health conditions that put you at greater risk of severe illness with coronavirus?

Woman with underlying health conditions shielding at home
(Image credit: Getty Images/Westend61)

Since the beginning of the virus outbreak, we've been aware that Covid-19 affects people with underlying health conditions more than others.

In fact, they're one of the main reasons why Covid-19 affects people differently. Those with the most serious illnesses are significantly more like to experience the most severe symptoms of coronavirus and be dangerously unwell. It's because of this that anyone with a major underlying health condition was asked to shield in the first lockdown and then again in the third lockdown, when cases began to rise again because of the new variants.

Now one year into the pandemic, we know more about how Covid-19 affects those with underlying health conditions than ever before.

What are underlying health conditions?

Put simply, underlying health conditions are long-term illnesses that people already have, which affect their health adversely. Multiple studies have shown that if they were to contract Covid-19, they would be seriously at risk as the majority of the illnesses already affect the body's ability to fight off infection.

Family with underlying health conditions looking at laptop screen

Credit: Getty

The NHS has separated the conditions into two categories: high risk (clinically extremely vulnerable people) and moderate risk (clinically vulnerable people).

People at high risk from Covid-19 (clinically extremely vulnerable)

  • Those who've had an organ transplant
  • People having chemotherapy or antibody treatment for cancer, including immunotherapy
  • People having an intense course of radiotherapy (radical radiotherapy) for lung cancer
  • People having targeted cancer treatments that can affect the immune system (such as protein kinase inhibitors or PARP inhibitors)
  • Those who've have blood or bone marrow cancer (such as leukaemia, lymphoma or myeloma)
  • Those who've had a bone marrow or stem cell transplant in the past 6 months, or are still taking immunosuppressant medicine
  • People who've been told by a doctor you have a severe lung condition (such as cystic fibrosis, severe asthma or severe COPD)
  • People who have a condition that means you have a very high risk of getting infections (such as SCID or sickle cell)
  • Those who are taking medicine that makes you much more likely to get infections (such as high doses of steroids or immunosuppressant medicine)
  • People who have a serious heart condition and are pregnant
  • People who have a problem with your spleen or your spleen has been removed (splenectomy)
  • Adults with Down's syndrome
  • Adults who is having dialysis or has severe (stage 5) long-term kidney disease

Anyone in this group should have received a letter from their GP at the beginning of the first lockdown, highlighting their risk and instructing them to shield.

Additionally, those eligible for a third Covid vaccine in this group will be told how to book a booster jab online before the end of the year.

People at moderate risk (clinically vulnerable)

  • Adults aged 70 or older
  • Those who have a lung condition that's not severe (such as asthma, COPD, emphysema or bronchitis)
  • Those who have heart disease (such as heart failure)
  • People who have diabetes
  • Those who have chronic kidney disease
  • Those who have liver disease (such as hepatitis)
  • People who a condition affecting the brain or nerves (such as Parkinson's disease, motor neurone disease, multiple sclerosis or cerebral palsy)
  • People a condition that means they have a high risk of getting infections
  • Anyone who is taking medicine that can affect the immune system (such as low doses of steroids)
  • Anyone who is seriously overweight (a BMI of 40 or above)
  • Anyone who is pregnant

Of course, being pregnant is not a health condition, but it's thought that carrying a child at the moment could make you more vulnerable during the pandemic. It's one of the reasons that there was so much debate around pregnancy and the Covid-19 vaccine when it first became available.

Pregnant woman

Credit: Getty

People in this less severe group won't have received a letter from their GP suggesting that they shield. However, they have been advised to take more precautions.

Why are people with these conditions at higher risk when it comes to Covid-19?

People with underlying health conditions are more at risk because they already have illnesses that affect the immune system and/or the respiratory system.

Someone who has had an organ transplant, for example, takes immunosuppressants to stop their bodies rejecting the organ. While these are essential, they do prevent the immune system from working as it naturally should, so they have no natural defence against the virus. Similarly, those on intensive cancer treatments will be taking drugs that compromise their immune systems, to ensure that the treatment works to fight the disease.

While those with severe lung conditions are at risk because Covid-19 is a respiratory virus. It enters through the nose or mouth and can go on to infect the upper or lower part of the respiratory tract. The respiratory tract is vital for breathing as it contains the tiny air sacs called alveoli, where oxygen is absorbed into your blood from the air and carbon dioxide is let out. So when this area become infected by the virus, it gets irritated and inflamed and can seriously damage the alveoli - impacting the person's ability to breath. This is one of the main causes of long Covid.

Someone with cystic fibrosis, for example, already has a similar problem in their lungs. As the Cystic Fibrosis Trust explains on their website, there is a thin layer of mucus that helps your body move dirt and bacteria out of the lungs when your lungs are healthy. People with cystic fibrosis have much thicker mucus that clogs their lungs, forming the ideal environment for harmful bacteria.

People with the condition may have restricted lung function due to thickening of the respiratory track and have frequent lung infections. Some people with cystic fibrosis also go onto have lung transplants as well, so they are on immunosuppressants which suppress the immune system. If they were to contract Covid-19, this would put further pressure on an already heavily compromised respiratory system.

Person putting pill into hand

Credit: Getty

However, people without such serious conditions are also at risk from Covid-19 - for quite similar reasons. Those aged over 70 years old are proven to have less effective immune systems than younger people and those with even mild asthma have compromised respiratory systems, making it harder to fight off infection.

Is MS an underlying health condition?

Multiple sclerosis (MS) does count as an underlying health condition, as it affects the brain and spinal cord. However, according to the MS Society, some people people with the condition are more at risk than others.

"This could be because of a particular treatment or the way your MS affects you. Or it could be a combination of things." They explain on their website, adding that anyone meeting the following requirements may be seriously at risk.

Those with MS who are at risk from coronavirus:

  • Anyone who has significant difficulties with breathing or swallowing (for instance if they need artificial feeding)
  • Anyone who has taken alemtuzumab (Lemtrada) within the last 4 weeks (or longer if specified by a clinician)
  • Anyone who has had HSCT treatment in the last 12 months (MS society advises these people to speak to their MS team to understand at what point their risks will reduce)
  • Anyone who has taken cladribine (Mavenclad), ocrelizumab (Ocrevus) or alemtuzumab (Lemtrada) within the last 6 months
  • have taken cladribine (Mavenclad), ocrelizumab (Ocrevus) or alemtuzumab (Lemtrada) within the last 6 months and has two of the high risk factors associated with MS.

For more information on Covid-19 and multiple sclerosis, visit the MS Society's coronavirus support page.

Woman in wheelchair sitting at a desk

Credit: Getty

16 - 65 with underlying health conditions: When will I get the vaccine?

Anyone aged 16 to 65 years old with an underlying health condition should receive their vaccine anytime from February 15. Those who are clinically extremely vulnerable should have already been vaccinated with either the Pfizer vaccine or the Oxford vaccine, as they were in the top 4 priority groups.

A statement from NHS England reads, "NHS staff will begin vaccinating people aged 65 to 69 and those who are clinically vulnerable against COVID from tomorrow (Monday February 15) with over one million people already invited to book a jab.

"Almost 1.2 million letters were due to land on doorsteps by yesterday (Saturday February 13) asking people to log on to the national booking service at www.nhs.uk/covid-vaccination with another 1.2 million due to arrive this week.

"Anyone unable to book online can call 119 free of charge, anytime between 7am and 11pm seven days a week.

"Those who receive a letter can choose from more than 100 large scale vaccination centres or almost 200 pharmacy services.

"In the next phase which begins tomorrow (Monday February 15), GP led vaccination sites will focus initially on the clinically vulnerable from cohort 6 because of the relationship between general practice and those with long term conditions, and continuity of care.

Young people with underlying health conditions walking down a road together

Credit: Getty

The vaccination rollout has been largely considered a huge success so far, as the government met their target to vaccine 15 million people in the top 4 priority groups by February 15. They are now going onto vaccinate those aged 16 to 65 with underlying health conditions.

New shielding list

In February, the government asked a further 1.7 million people in the UK to begin shielding again. This number was on top of the 2.3 million people who were already doing so as part of the lockdown guidelines, first introduced at the beginning of 2021.

It comes as a new model has been developed by the NHS to take into account extra factors that put someone more at risk from Covid-19, apart from their health. While it does take underlying health conditions into account, it also looks at:

  • Ethnicity
  • Deprivation (worked out by postcode)
  • Weight
  • Age
  • Prescribed medications

Until February, only those with the specific conditions outlined above were told to shield until March 21. The new model takes these other factors into account, after researchers from Oxford University looked at the characteristics of people who died from Covid-19 in the first wave to better understand their risk from the virus.

People newly found to be at risk have been identified by medical records and from now on, should be sent letters from the NHS informing them of their new risk status. This means that they will also now likely be entitled to statutory sick pay, where they previously might not have been, as well as prioritisation for online shopping slots and the vaccine.

Senior Digital Writer

Amy is Senior Digital Writer across Woman & Home, GoodTo and Woman, writing about everything from celebrity news to health, fashion and beauty features. When she isn't obsessing over the latest dress drop from Marks & Spencer, you'll most likely find Amy out running, or with a cup of tea in hand ready to dive into a gripping new Netflix series.