SciMoms COVID FAQs: Who is at high-risk for COVID-19?

In this series of COVID FAQs, the SciMoms answer your frequently asked questions about the novel coronavirus or COVID-19 pandemic. For our third FAQ, we focus on high-risk groups for COVID-19.

Defining risk: it’s not about you

Risk is a population-based measure, which means it doesn’t necessarily apply to every individual in that population. Since risk is population-based, it doesn’t apply to every individual in that category. When scientists evaluate “risk”, they’re measuring the likelihood of harm in a group of people. Risk does not measure an individual’s chances of becoming sick.

Within a group, we cannot make specific predictions about whether a particular individual in that population will develop a mild or serious case. We can predict how many within that group are likely to develop a mild or serious case.

As scientists learn more, we may be able to refine high-risk categories, but it is unlikely that we will be able to predict exactly what the disease will look like in any particular individual.


Risk In Perspective: Population risk does not equal individual risk

What does the term high risk mean?

“High risk” refers to people who are more likely to become severely ill if they become infected. People who are “high risk” for COVID are older adults and people of any age with certain underlying medical conditions.

Who is high risk for COVID-19?

According to the CDC, the underlying medical conditions that make people high risk for COVID include:

  • Chronic kidney disease
  • COPD (chronic obstructive pulmonary disease)
  • Immunocompromised state (weakened immune system) from solid organ transplant
  • Obesity (body mass index [BMI] of 30 or higher)
  • Serious heart conditions, such as heart failure, coronary artery disease, or cardiomyopathies
  • Sickle cell disease
  • Type 2 diabetes mellitus
  • Children who are medically complex, who have neurologic, genetic, metabolic conditions, or who have congenital heart disease

However, COVID-19 is a new disease. As a result, there is limited information about the impact of underlying medical conditions and whether these conditions increase the risk for severe illness from COVID-19. Based on what we know at this time, people with the following conditions might be at an increased risk for severe illness from COVID-19:

  • Asthma (moderate-to-severe)
  • Cerebrovascular disease (affects blood vessels and blood supply to the brain)
  • Cystic fibrosis
  • Hypertension or high blood pressure
  • Immunocompromised state (weakened immune system) from blood or bone marrow transplant, immune deficiencies, HIV, use of corticosteroids, or use of other immune weakening medicines
  • Neurologic conditions, such as dementia
  • Liver disease
  • Pregnancy
  • Pulmonary fibrosis (having damaged or scarred lung tissues)
  • Smoking
  • Thalassemia (a type of blood disorder)
  • Type 1 diabetes mellitus


People Who Are at Increased Risk for Severe Illness

OpenSAFELY: factors associated with COVID-19 death in 17 million patients

What are “vulnerable populations”?

The WHO defines vulnerability as “the degree to which a population, individual or organization is unable to anticipate, cope with, and recover from the impacts of disasters.” Vulnerable populations are categories of people that are less able to anticipate, cope with, and recover from those impacts.

According to the CDC, these populations may include: people who have difficulty communicating, people who have difficulty accessing medical care, people who need help maintaining independence, and people who require constant supervision or who may need help accessing transportation. 

Depending on the specific context, vulnerable populations in health care and research may include the economically disadvantaged, racial and ethnic minorities, the uninsured, low-income children, the elderly, the homeless, those with human immunodeficiency virus (HIV), individuals with chronic health conditions including severe mental illness, children, prisoners, and those with cognitive impairment. Some of these populations are also at high risk for severe cases of COVID-19 because members of these communities have higher rates of the underlying conditions that put them at higher risk. Some of these populations are also more likely to be exposed to and contract COVID-19 for a wide range of sociological and economic reasons.


Vulnerable groups

Emergency Preparedness & Vulnerable Populations: Planning for Those Most at Risk

What does blood type have to do with COVID-19? 

In early June, the genetic service company 23andme shared preliminary data suggesting that people with Type O blood might have a reduced risk of contracting COVID-19. This difference was very small in their dataset –  a 9-18% reduction in risk for people with Type O blood. When they graph the percentage of cases in each of the blood types, you can see clearly how tiny this difference is. 

A recently published study also found lower risk of contracting COVID-19 for people with Type O blood, but these differences were too small to be meaningful. No one should take this to mean that any individual with Type O blood is protected against the disease.

This same study also found no effects of blood type on the severity of COVID-19, indicating that blood type does not influence disease outcomes. This means that knowing a patient’s blood type is not useful for doctors to predict the course of the disease.

While this data on blood types is intriguing scientifically, the effect is too small to be a useful predictor of someone’s chance of being infected. Blood type should not be used as a justification to ignore the recommended precautions for washing your hands, wearing a mask, and watching your distance. 


23andMe finds evidence that blood type plays a role in COVID-19

Blood type and outcomes in patients with COVID-19

Does Blood Type Affect Your Risk Of Coronavirus? Probably Not, New Studies Say

Are men at higher risk of COVID-19 than women?

Yes, men are more likely to be hospitalized with severe COVID-19 and more likely to die from it. This is not because men are infected more often than women. Women contract the virus at the same rates as men but are more likely to recover. This is true across ages and around the world.

It is not clear at this point why there is this sex difference in disease severity. Some hypotheses that scientists are exploring include:

  • There are well-documented sex differences in the immune responses to viruses that may be a factor in the differing severity of COVID-19.
  • There may be sex differences in levels of ACE2, the receptor that SARS-CoV2 uses to infect human cells. If males have higher levels of ACE2, this could explain why males tend to have more severe disease.
  • Many underlying conditions that are considered high-risk for COVID-19 are more common in males than females.
  • A variety of social and lifestyle factors may play a role.


Why COVID-19 poses greater risks for men than women

The Science of How COVID-19 Affects Us Differently

Are kids at lower risk?

Yes, kids are not in a high-risk category. They are more likely to have mild cases of COVID-19. However, this does not mean that all kids have mild cases. In one study, 10% of infants with a positive COVID test became critically ill.

Kids also may be less likely to get COVID-19. However, this data is all very preliminary and, for now, there are no clear answers. The lower number of cases in kids could be due to a milder course of disease and a larger percentage of asymptomatic cases in kids, a lower risk of getting infected, or social distancing measures that have kept kids safe (or a combination of these).

Why do kids tend to have milder symptoms?

The reasons why kids tend to have milder symptoms remain unclear. In a new study that looked at the cells in the lining of kids’ noses compared to adults, researchers found that in kids, these cells had less gene expression of the ACE2, which encodes the protein that SARS-CoV2 is thought to use to get into cells. So if kids, in general, have less of this protein, the virus might just not be able to get into the host cells. But this is very preliminary as they haven’t looked at actually protein levels or reduced activity of ACE2. Some people also suspect that the differences in adult and child immune systems might contribute. But the science in this area is still very new and developing.

What is multisystem inflammatory syndrome in children?

There have also been reports of multisystem inflammatory syndrome in children (MIS-C) in some kids with COVID-19, which has symptoms like Kawasaki disease. According to the CDC, MIS-C is “a condition where different body parts can become inflamed, including the heart, lungs, kidneys, brain, skin, eyes, or gastrointestinal organs.”

It is critical that you contact your child’s doctor, nurse, or clinic right away if your child is showing symptoms of MIS-C or COVID-19. Emergency warning signs include: 

  • Inability to wake up or stay awake
  • Difficulty breathing
  • Chest pain or pressure that doesn’t go away
  • New confusion
  • Bluish lips or face
  • Severe stomach pain

If your child is experiencing these symptoms, call 911 or go to the emergency room immediately.

I’ll reiterate here that risk is a population-based concept. So while more young people have mild cases, we just don’t have enough information to predict which kids will have a mild case and which will develop severe complications like MIS-C. This means we all have to be vigilant.


Coronavirus in Babies & Kids

COVID-19 Is “Very Different” in Young Kids Versus Adults

Multisystem Inflammatory Syndrome in Children (MIS-C)

Multisystem inflammatory syndrome in children (MIS-C) and COVID-19

Studies find nearly 300 kids with inflammatory condition tied to Covid-19

Why do some people have mild symptoms, others have severe symptoms, and some people have no symptoms?

We know that most cases of COVID-19 are mild and a third to a half of all SARS-CoV2 infections are asymptomatic (or produce symptoms that are so mild that people don’t necessarily think of them as symptoms). 

While we know that certain groups of people are more likely to have severe symptoms, we also know that not all people who get COVID-19 in those groups develop severe symptoms. There are clearly individual differences that we don’t yet understand. As discussed in the answers above, scientists are looking at many possible explanations for why the spectrum of symptoms is so varied: genetic differences, differences in ACE2 expression, and differences in immune response and inflammation pathways. 

Why does COVID-19 affect some socioeconomic groups and cultural communities more than others?

COVID-19 is not alone in that it affects vulnerable communities more. Health disparities are a huge problem in the US with higher illness and death rates for racial minorities. The current pandemic puts these long-standing inequities on stark display.

According to the CDC, age-adjusted hospitalization rates for COVID-19 show acute disparities for racial minorities in the US: 

  • Non-Hispanic Native American or Alaskan Native persons have a rate approximately 5 times that of non-Hispanic white persons,
  • Non-Hispanic black persons have a rate approximately 5 times that of non-Hispanic white persons,
  • Hispanic or Latino persons have a rate approximately 4 times that of non-Hispanic white persons.

The reasons for these disparities are multi-faceted. Some factors that lead to health disparities include a lack of access to affordable health insurance and health care, institutionalized racism in our scientific and medical communities, and our society as a whole, disparities in education, higher exposures to harmful environmental factors, living conditions, and work circumstances. 

To be clear, the reason for these disparities is racism, not race itself.


COVID-19 in Racial and Ethnic Minority Groups

Covid-19 lays bare how racism fuels health disparities among Black people

What needs to happen to reduce the disparities in harder-hit communities?

This is a huge question that extends well beyond the scope of COVID-19 and the current pandemic.

This page from CDC includes suggestions for reducing the impact of COVID-19 in minority groups for public health professions, community organizations, healthcare systems and providers, and the general public.

As a person who is not in a position of power or influence, how can I help communities with higher levels of COVID-19 risk?

Practically, follow all the recommendations to protect your entire community. Only go out when necessary, wear a mask, wash your hands, watch your distance, and don’t gather indoors. 

More broadly, learn and talk about issues related to social determinants of health, health equity, implicit biases, and institutional racism. Extensive resources have been collected here

Reflect on your own privilege in your response to the pandemic by considering: 

  • Are you part of a vulnerable community that has higher rates of all the underlying health problems that put people at higher risk of developing a severe case of COVID-19? 
  • Do you have the luxury of a job that lets you work remotely? 
  • Can you afford to take time off from your job and still make ends meet? 
  • Do you have the privilege of living in a big house where staying at home is comfortable? 
  • Does your job provide health insurance?
  • Do you have the financial resources and the space to stock up on food so you don’t need to go to the store frequently? 
  • Are you at risk of losing your job if you get sick?
  • Do you have access and can you afford childcare? 

This is just the beginning of topics you can think about.


How can I help communities with higher levels of COVID-19?


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