Why Comorbidities Are a Risk Factor for Developing Severe COVID-19

When vaccines for COVID-19 first became available, states prioritized at-risk populations, including people with comorbidities and underlying conditions. Certain people with comorbidities were eligible to receive the vaccine before others to provide extra protection to those who were more likely to experience severe cases of COVID-19 or death.

But what are comorbidities—and how do they affect COVID-19? Here's what experts told us, plus how to know if you have one.

Comorbidities Definition

"Comorbidities are the presence of two or more diseases in the same person," Jooby Babu, MD, pulmonologist and critical care specialist at Providence St. Joseph Hospital in Southern California, told Health. "For instance, a person who has diabetes and hypertension, or diabetes and kidney failure."

In the case of COVID-19, if a person had COVID-19 and another disease or condition, then COVID-19 and the other condition would be comorbidities. So, for example, if a person had diabetes and then developed COVID-19, they would have two diseases—or comorbidities.

The term comorbidity was first documented in the 1970s by the renowned doctor and epidemiologist A.R. Feinstein, who used the term when referring to people who suffered from rheumatic fever and multiple other diseases.

Comorbidities and COVID-19

A disease weakens the body's systems, making it difficult for the body to eliminate the cause of the disease and fight invaders like viruses and bacteria. When two or more conditions are present at the same time, this can be very taxing on the body, and the affected person may need longer to recover than someone who does not have comorbidity.

After the start of the pandemic, researchers began studying the link between people with certain comorbidities and the COVID-19 disease. In September 2020, a study published in PLoS Medicine examined more than 31,000 adult patients in the US and found that comorbidities with COVID-19 put people at a higher risk of mortality.

Comorbidities are a serious health concern, said Dr. Babu, because the presence of two or more conditions increases the chances of hospitalization and the risk of death and affects the quality of life. When a person experiences comorbid conditions, they may have a compromised immune system or need additional care that exposes them to others. Plus, they may already be experiencing complications from the underlying condition that puts increased stress on their body. According to a study published by the Annals of Family Medicine, "Comorbidity is associated with worse health outcomes, more complex clinical management, and increased health care costs."

CDC List of Comorbid Conditions

The Centers for Disease Control and Prevention (CDC) provide a list of comorbid conditions in COVID-19 patients. The list is extensive and divides known comorbidities into risk categories based on current data.

Conditions, where there is good-to-strong data for a more severe COVID-19 outcome, include:

  • Asthma
  • Cancer
  •  Cerebrovascular disease—diseases and conditions that affect blood flow throughout the body, such as clotting conditions
  • Chronic kidney disease
  • Chronic lung diseases, such as chronic obstructive pulmonary disease (COPD)
  • Chronic liver diseases, such as liver cirrhosis
  • Cystic fibrosis
  • Type 1 and 2 diabetes
  • A number of disabilities, such as cerebral palsy, spinal cord injuries, and disabilities that affect the ability to care for oneself, among others
  •  Various heart conditions, such as heart failure and coronary artery disease
  • Human immunodeficiency virus (HIV)
  • Mental health conditions, such as depression and schizophrenia
  • Dementia
  • Obesity
  • Primary immunodeficiencies—disorders that impact the way an individual’s immune system functions
  • Pregnancy, including recent pregnancies
  • Not being physically active
  • Smoking, including whether you currently smoke or smoked previously
  • Past history of organ or stem cell transplant
  • Tuberculosis
  • If you currently use corticosteroids or other medications that can decrease your immune system’s ability to respond to infections—i.e., immunosuppressive medications

Conditions where there are data to suggest a higher risk of more severe COVID-19 outcomes, but the data for conditions are not as substantial as the previous list:

Conditions that may be associated with a higher risk of more severe COVID-19 outcomes, but the evidence is mixed, or the data are limited include:

  • Alpha 1 antitrypsin deficiency (a condition where your liver does not make enough of a protein that protects your lungs and can lead to lung disease)
  • Bronchopulmonary dysplasia (a chronic lung disease)
  • Hepatitis B and C

A July 2021 study conducted by the CDC involved more than 500,000 patients hospitalized with COVID-19 from March 2020 to March 2021 and identified several risk factors for death. The strongest risk factors in this study were obesity, anxiety and fear-related disorders, and diabetes with complications. The study also found that the risk of death increased with the number of comorbidities.

Comorbidities and the Vaccine

The opportunity to get the COVID-19 vaccine came as welcome news to those who live with chronic health conditions. For Dr. Babu, it was an important development. "Patients with comorbidities should get vaccinated as early as possible," said Dr. Babu.

Vaccination against COVID-19 is also effective in breakthrough infections. A breakthrough infection is when someone who has fully vaccinated contracts the disease. Vaccination can decrease the severity of COVID-19 and hospitalizations, as was seen in the results of a December 2021 study published in JAMA Internal Medicine. This study examined electronic medical record data from a large US sample of vaccinated immunocompromised individuals.

Ways to Prevent COVID-19 Infections

If you live with a chronic health condition, it's even more important that you follow the hygiene and safety guidelines set out by the CDC. These guidelines include limiting person-to-person contact, wearing masks in public areas, and being vigilant about handwashing with soap and water or using hand sanitizers.

Other measures listed by the CDC as important to help keep yourself safe if you live with a chronic health disease or condition are:

  • Ensure you are vaccinated and up to date on any boosters, you are eligible for
  • Ask a healthcare professional about any antiviral medications you may be eligible for if you do become sick with COVID-19
  • Ensure you regularly see your healthcare professionals for routine appointments and concerns
  • Ask a healthcare professional about opportunities for telehealth appointments (if you feel comfortable with this) to limit exposure to others
  • Consider wearing a high-quality mask, even if mask restrictions have lessened in your area, since you may be at a higher risk if you contract COVID-19

It's also important to reduce the risk of medication interactions, so if you live with multiple conditions or disorders, make sure your doctor knows all prescribed meds and over-the-counter drugs you're taking.

A Quick Review

It is important to be aware if you have a condition that may make a COVID-19 infection more severe. However, know there are many steps you can take to decrease your risk of catching COVID-19. There are also treatments, such as antivirals, that you may be eligible for if you are a higher-risk individual.

Make sure you keep your appointments with your healthcare team to manage your current condition(s). And, if you are concerned you have a COVID-19 infection, reach out to a healthcare professional for advice.

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDCWHO, and their local public health department as resources.

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Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Feinstein AR. The pre-therapeutic classification of co-morbidity in chronic disease. Journal of Chronic Diseases. 1970;23(7):455-468. doi:0.1016/0021-9681(70)90054-8

  2. Harrison SL, Fazio-Eynullayeva E, Lane DA, Underhill P, Lip GYH. Comorbidities associated with mortality in 31,461 adults with COVID-19 in the United States: A federated electronic medical record analysis. Kretzschmar MEE, ed. PLoS Med. 2020;17(9):e1003321. doi:10.1371/journal.pmed.1003321

  3. Jose M. Valderas, Barbara Starfield, Bonnie Sibbald, Chris Salisbury, Martin Roland. Defining comorbidity: Implications for understanding health and health services. The Annals of Family Medicine. Jul 2009, 7 (4) 357-363; doi:10.1370/afm.983

  4. Centers for Disease Control and Prevention. Underlying medical conditions associated with higher risk for severe COVID-19: Information for healthcare professionals.

  5. National Heart, Lung, and Blood Institute. Alpha-1 antitrypsin deficiency.

  6. Centers for Disease Control and Prevention. Underlying medical conditions and severe illness among 540,667 adults hospitalized with COVID-19, March 2020-March 2021.

  7. Kim AHJ, Nakamura MC. Covid-19 breakthrough infection among immunocompromised persons. JAMA Intern Med. 2022;182(2):163. doi:10.1001/jamainternmed.2021.7033

  8. Centers for Disease Control and Prevention. How to protect yourself and others.

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