What Is a Weak Immune System? Here's How Doctors Explain It


The immune system is essentially the body's defense mechanism—its job is to protect us against pathogens (viruses, bacteria, or other microorganisms that cause disease) to keep us as healthy as possible. For most young, healthy people, the immune system succeeds in doing this—but sometimes, the immune system doesn't work as well as it should, leaving individuals more susceptible to illness.

The immune system is front-and-center right now in the fight against COVID-19, due in large part to how dangerous the virus can be for people with weakened immune systems, or those who are immunocompromised. But what exactly does it mean to have a weak immune system, and what causes it? Health asked experts what you need to know about being immunocompromised, and how to protect yourself or someone you know with a weak immune system safe during the COVID-19 pandemic—and after it.

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What causes a weak immune system?

In order to understand what can cause a weakened immune system, you first have to know about one of the immune system's key players: white blood cells. According to the National Institute of Allergy and Infectious Diseases (NIAID), immune cells (aka, white blood cells) are constantly circulating in your body, via your bloodstream, looking for issues.

Most of the time, those white blood cells do their job, seeking out foreign invaders and protecting the body against them. But many different illnesses can affect the functioning of white blood cells, Donald Ford, MD, a family medicine doctor at Cleveland Clinic, tells Health. Among these are chronic conditions like diabetes and cancer, as well as infections, such as HIV. Other conditions, including some autoimmune diseases like lupus or rheumatoid arthritis, can also cause a weak immune system.

The immune system can also be weakened by certain medications like corticosteroids, which are used to combat inflammation in the body, Tania Elliott, MD, clinical instructor of medicine at NYU Langone, tells Health. In fact, the job of corticosteroids is to "inhibit the activity of the white blood cells," says Dr. Ford, which is why those drugs weaken the immune system. Other medications that can weaken the immune system include chemotherapy medications and biologics, says Dr. Elliott. It should be said that, while these medications do affect a person's immune system, they're prescribed because their disease-fighting or controlling benefits outweigh any possible downsides.

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What can be done to protect people with weak immune systems?

First and foremost: It's important to consider those with weak immune systems all the time, not just during a pandemic like COVID-19. The flu is another virus that, similarly to the coronavirus, affects immunocompromised individuals more so than those with healthy immune systems.

If you or someone you know is immunocompromised, the best way to stay healthy is to limit contact with sick people as much as possible. That's why it's so important for everyone to stay home when sick, and why, especially right now, US health officials have encouraged everyone to practice social distancing to protect friends and loved ones who may be at greater risk for serious illness from COVID-19 due to underlying conditions.

Other ways to protect those with weakened immune systems during this time—whether it's yourself or someone you know—includes wearing a mask when out in public (or in your home, if you have to be around someone who is ill), minimizing physical interactions with those outside of your family, and washing your hands often, says Dr. Elliott. It's also important to keep the often-touched surfaces in your home clean and sanitized, according to the CDC, to prevent any contact with the virus.

It's also important for immunocompromised people to stick with their treatment plans—especially during a public health crisis, but also in general—according to the CDC. That means not stopping any medications or treatments without first talking to your doctor, because the immune system is healthier when underlying disease is in a well-maintained state. The CDC also recommends keeping anxiety and stress levels under control, and to keep up other healthy habits like proper nutrition and regular exercise—a benefit to both those with weakened immune systems and those without.

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