What Medications Weaken Your Immune System, and Why? - GoodRx (2024)

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 its ability to protect us.

Due to COVID-19, you’ve likely heard a lot about weakened immune systems and vaccine effectiveness. You may be wondering if any of your medications can weaken your immune system. You could also be curious if certain vaccines — like the COVID-19 vaccine — will work if your immune system is less active than normal.

In this article, we discuss which medications can weaken your immune system. Plus, we'll review if certain vaccines are effective if you have a weakened immune system.

What does it mean to have a weakened immune system?

Your immune system helps your body fight off infections. There are many elements to your immune system. Having a weakened immune system means your body isn’t able to defend against infections as well as usual. This is sometimes referred to as being “immunocompromised.”

Having a weakened immune system can cause you to have frequent infections. It can also raise your risk for serious infections. Some people may be born with a weakened immune system. But sometimes, certain health conditions or medications cause this condition.

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 actually be helpful in certain conditions. For example, some people take immunosuppressants after receiving an organ transplant. This helps prevent the immune system from attacking the new organ.

Immunosuppressants are also used as treatments for people with certain conditions caused by an overactive immune system. This includes lupus and rheumatoid arthritis (RA).

But in other cases, immunosuppression is a side effect of certain medications.

What types of medications can weaken your immune system?

Many medications can weaken your immune system. Common examples of immunosuppressants are discussed below.

Biologics and biosimilars

Biologics are medications made of living cells from humans, animals, or microorganisms. This is in contrast to “traditional” medications that are made using simple chemicals.

A biosimilar is like a generic medication. Generic medications contain an exact copy of the active ingredient in a brand-name medication. But because biologics come from living cells, it’s not possible to make an exact copy of it. Still, a biosimilar works the same way as the biologic that it’s based on, even if it isn’t an exact copy.

There are many different biologics and biosimilars available. They work in several ways. And the way they might weaken your immune system depends on the medication.

For example, certain ones treat autoimmune conditions like RA. Autoimmune conditions are caused by an overactive immune system. Biologics and biosimilars can often “turn down” your immune system for treatment.

These medications generally block certain immune system proteins that “turn on” your immune system. But a potential consequence of doing this is developing a weaker immune system.

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

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

• Etanercept (Enbrel) and etanercept-szzs (Erelzi)

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

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

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

But not all biologics and biosimilars weaken your immune system. For example, erenumab (Aimovig) is a biologic medication that can help prevent migraines. Aimovig’s manufacturer says that 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 your healthcare provider.

Corticosteroids

Corticosteroids are a class of medications that can treat a wide variety of health conditions, including:

• Allergic reactions

• Asthma

• Chronic obstructive pulmonary disease (COPD)

• Inflammatory bowel disease

• Lupus

• Multiple sclerosis

• Organ transplant

• RA

These medications are made to work like natural steroid hormones in your body. But corticosteroids can have immunosuppressive effects. This isn’t surprising based on how these medications work.

Corticosteroids lower the amount of immune system cells and enzymes (chemicals) that your body makes. This can make your immune system less active and reactive.

This is useful in certain situations, such as after receiving an organ transplant. But it also means you’re more likely to get an infection.

Your risk for immunosuppression appears to go up with higher doses and long-term use. This risk doesn’t usually apply to short-term use of corticosteroids, such as using them for a few days to treat a COPD flare.

Examples of common corticosteroids are prednisone, dexamethasone, and methylprednisolone.

Chemotherapy

Chemotherapy refers to a large group of medications that are often used to treat cancer.

In general, chemotherapy medications work by stopping cells in your body from replicating and growing. This affects fast-growing cells like cancer cells. Chemotherapy kills cancer cells and stops them from growing in your body.

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

Examples of chemotherapy medications include:

• Carboplatin

• Capecitabine

• Cyclophosphamide

• Docetaxel

• Doxorubicin

• Pacl*taxel

• Vincristine

Organ transplant medications

Medications used after an organ transplant are intentionally used to weaken your immune system. While this may sound scary, it’s actually vital to protecting the transplanted organ.

Left to its own devices, your immune system would identify a transplanted organ as “foreign.” It would mount an attack against the organ for self-defense. This is known as organ rejection.

This can happen as soon as one week after transplant, but the risk is highest during the first three months. It can also occur months or even years after a transplant surgery.

To help prevent rejection, you can take certain medications after an organ transplant. These medications weaken your immune system in different ways.

In general, they work by reducing activity in your immune system. But unfortunately, 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 I’m taking an immunosuppressant, should I worry about COVID-19 vaccine effectiveness?

Not typically.

COVID-19 vaccines may provide less protection if you have a weakened immune system. But this doesn’t mean they lose all effectiveness. In many cases, you’ll likely need an extra COVID-19 vaccine dose to help make up for this difference.

The Centers for Disease Control and Prevention (CDC) recommends everyone age 5 and older to get fully vaccinated against COVID-19. This includes people with weakened immune systems. People who are immunocompromised are at higher risk for severe COVID-19 if you test positive for the virus. This includes people taking medications that weaken your immune system.

Your healthcare provider can help answer questions you may have about COVID-19 vaccines, including which vaccines you should receive and when. This includes choosing which additional primary shot or booster shot to get if you’re considered moderately to severely immunocompromised.

What about the flu shot?

The CDC recommends 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.

But people taking medications that weaken your immune system should avoid getting the 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.

Any of the currently available flu shots are OK if you have a weakened immune system. Unlike the nasal spray vaccine, flu shots contain inactivated (dead) flu virus that can’t cause you to get the flu.