4 Types of Medications That Suppress the Immune System: Corticosteroids, Chemotherapy, and More

Our immune system stands guard at all times, watching and waiting for germs to try to take hold and make us sick. But certain health conditions and medications can weaken our immune system. This hurts our body’s ability to protect us.

Here, we discuss which medications can weaken your immune system. Plus, we'll review whether vaccines are effective if you have a weakened immune system.

What does it mean to have a weakened immune system?

Your immune system helps protect your body from infection. When it’s weak, your body has a harder time fighting germs, such as bacteria, viruses, and fungi. This is called being "immunocompromised."

A weakened immune system can lead to more frequent infections and a higher risk of falling seriously ill. Some people are born with a weakened immune system, but it can also be caused by certain health conditions and medications.

What is an immunosuppressant?

An immunosuppressant is a medication that weakens your immune system. It does so by making your immune system less active.

This can be helpful for certain conditions. For example, people who receive an organ transplant typically need to take immunosuppressants to stop their immune system from attacking the new organ. Immunosuppressants are also used to treat certain conditions where the immune system is too active, such as lupus and rheumatoid arthritis (RA). 

In other cases, immunosuppression can be an unintended side effect of a medication.

1. Biologics and biosimilars

Biologics are medications made of living cells from humans, animals, or microorganisms. This makes them different from “traditional” small molecule medications, which are made using chemicals.

Many reference (“brand name”) biologics also have biosimilars. You can think of biosimilars as a generic version of a biologic. However, since biologics come from living cells, it’s not possible to make exact copies of them.

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Many biologics and biosimilars are available. These medications generally work by blocking specific immune system proteins that “turn on” your immune system. They’re often prescribed in more severe cases of inflammation. But a potential consequence of doing this is weakening your immune system.

Examples of biologics and biosimilars that can weaken your immune system include:

• Adalimumab (Humira) and adalimumab-adbm (Cyltezo)

• Infliximab (Remicade) and infliximab-abda (Renflexis)

• Rituximab (Rituxan) and rituximab-arrx (Riabni)

• Trastuzumab (Herceptin) and trastuzumab-dkst (Ogivri)

Not all biologics and biosimilars weaken your immune system, though. For example, erenumab (Aimovig) is a biologic medication that prevents migraines. There’s no evidence that it weakens the immune system.

If you have questions about whether a specific biologic can weaken your immune system, talk to a healthcare professional.

2. Corticosteroids

Corticosteroids are a class of medications that treat a wide variety of health conditions, including asthma, chronic obstructive pulmonary disease (COPD), inflammatory bowel disease, and more. These medications are made to mimic natural steroid hormones in your body. Common corticosteroids include prednisone, dexamethasone, and methylprednisolone.

Corticosteroids can weaken your immune system. They do this by reducing the number of immune cells and chemicals your body makes. The risk of developing a weakened immune system due to corticosteroids increases with higher doses and long-term use.

Short-term use, like taking a corticosteroid for a few days to treat a COPD flare-up, doesn't generally carry a risk of immunosuppression.

3. Chemotherapy

Chemotherapy medications are used to treat cancer. They’re what most people think of when cancer treatments come to mind. These medications work by broadly stopping cancer cells from growing and dividing.

Unfortunately, healthy cells — including immune system cells — are affected by chemotherapy. Chemotherapy stops immune cells from growing and dividing, which weakens your immune system. This means people who receive chemotherapy are at higher risk for infection.

Examples of chemotherapy medications include:

• Carboplatin

• Capecitabine (Xeloda)

• Cyclophosphamide (Cytoxan)

• Docetaxel (Taxotere, Beizray, Docivyx)

• Doxorubicin (Doxil)

• Paclitaxel (Abraxane)

• Vincristine

4. Organ transplant medications

Organ transplant medications are prescribed to intentionally weaken your immune system. While this may sound scary, it’s actually necessary to protect a transplanted organ.

Left to its own devices, your immune system may recognize a newly transplanted organ as “foreign” to the body. It may try to attack it as a result. This is known as organ rejection. This can happen as soon as 1 week after transplant, but the risk is highest during the first 3 months. It can also occur months or even years after a transplant surgery.

To help prevent rejection, you can take medications after an organ transplant. In general, they work by reducing activity in your immune system. But they also hinder your immune system from responding to real threats. These include bacterial or viral infections.

Examples of organ transplant medications include:

• Azathioprine (Imuran)

• Cyclosporine (Sandimmune)

• Cyclosporine, modified (Gengraf, Neoral)

• Mycophenolate mofetil (CellCept)

• Mycophenolate sodium (Myfortic)

• Sirolimus (Rapamune)

• Tacrolimus (Prograf)

If you’re taking an immunosuppressant, should you worry about COVID vaccine effectiveness?

Not typically. Although COVID-19 vaccines may provide less protection if you have a weakened immune system, this doesn’t mean they lose all effectiveness. In many cases, an extra COVID vaccine dose may be recommended.

The CDC recommends everyone age 6 months and older to get vaccinated against COVID. This includes people with weakened immune systems. In fact, people who are considered immunocompromised are at higher risk for severe COVID.

A healthcare professional can help answer questions you may have about COVID vaccines, including which vaccines you should receive and the appropriate timing for your doses. This includes guidance on additional doses tailored to those who are considered moderately to severely immunocompromised.

What about the flu shot?

The CDC recommends almost everyone (with a few exceptions) age 6 months and older get an annual flu shot. This includes people who are immunocompromised. A weakened immune system raises your risk for serious complications if you get the flu.

While the flu shot may not work as well in people receiving certain immunosuppressants, it still offers some important protection.

The main exception is FluMist. People taking medications that weaken your immune system should avoid getting this nasal spray flu vaccine. This form of the flu vaccine contains live flu virus. If your immune system isn’t functioning well, you could actually get the flu.

Why trust our experts?

Written by:

Goldina Erowele, PharmD, MBA

Dr. Goldina Ikezuagu Erowele is a transformative leader in healthcare with a distinguished record of advancing medication safety, operational efficiency, and cost management.

Edited by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Reviewed by:

Amy B. Gragnolati, PharmD, BCPS

Amy Gragnolati, PharmD, BCPS, is a pharmacy editor for GoodRx. Amy currently holds her pharmacist license in Georgia and California.

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