Revealed: The common medications that make your flu shot less effective

Everyone is asked to get the flu shot every year to reduce the risk of infection and hospitalization.

And more than 100 million people are lining up for the vaccine, especially those 65 and older — with more than 70 percent of U.S. seniors getting the shot.

Although the flu shot is widely recommended, doctors advise people to be careful about the medications they take before or after being vaccinated because some medications can decrease the effectiveness of the vaccine.

There are more than 295 medications that can interact with flu shots and make them less effective, ranging from some over-the-counter pain relievers to treatments used to relieve pain from arthritis or to fight cancer.

Each year in the United States, approximately 41 million people become infected with the flu and 710,000 people are hospitalized. More than 36,000 people die from the infection – with up to 85 percent of deaths occurring among people aged 65 or over.

But flu vaccination coverage is declining in the US, largely due to the mass vaccination campaign and vaccine mandates during the Covid pandemic.

The latest data shows that only 45 percent of adults over the age of 18 received the vaccination in the 2023 to 2024 flu season, a two percent decrease from the year before.

Coverage hasn’t been this low since the 2017-2018 season, when 37.1 percent of adults signed up for a flu shot.

Health officials are calling for more people to get the flu vaccine this winter

Research shows that the flu shot was about 35 percent effective against hospital admissions due to the virus last year, which is lower than the average of about 50 percent.

Efficacy varies because experts have to guess which strain of flu is likely to be most common each season based on observations from the Southern Hemisphere – where it is winter when the North has its summer – but these are not always correct.

For those who do roll up their sleeves for the vaccine, experts recommend consulting a doctor and discussing medications that could interfere with the shot.

Below, DailyMail.com details some medications that may affect the effectiveness of your flu vaccine this season:

Pain medications

The discomfort or pain around the injection site caused by a flu vaccination may lead many to reach for an over-the-counter pain reliever.

These may include nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen – the active ingredient in Motrin and Advil – and naproxen – the active ingredient in Aleve.

A flu shot works by teaching the immune system to recognize and fight the flu virus.

Normally it contains an inactivated virus or a protein from the virus that is injected into the blood and causes an immune response, causing the immune system to produce antibodies (virus-fighting proteins) that remain in the body to fight the virus.

Doctors recommend avoiding NSAIDs after a flu vaccination because they can dampen the immune response by reducing antibody production.

This happens because the drugs suppress inflammation, which reduces the immune response to the vaccine.

Dr. David Topham, a doctor at the University of Rochester, said this university website: “Unless your healthcare provider tells you otherwise, it is best not to take pain relievers for one or two days before the flu vaccine and for a week afterward.”

Other painkillers such as acetaminophen – brand name Tylenol – should be safe to take after vaccination because they work differently in the body.

Prednisone

Prednisone is one of the most commonly used medications in the US. Approximately 20 million prescriptions for prednisone are written annually.

Pictured above are prednisone tablets. Doctors warn that certain types of these pills can make the flu vaccine less effective

It is a type of steroid and is used to reduce inflammation to relieve symptoms of many conditions, including arthritis, asthma, inflammatory bowel disease and in organ transplant patients.

But doctors say if someone takes more than 20 milligrams (mg) per day for two weeks or more, the flu vaccine may become less effective.

This is because, like some over-the-counter pain relievers, it can also reduce the body’s ability to form antibodies, weakening the immune response to the vaccine.

Jodie Pepin, clinical pharmacy program director at Harbor Health in Texas, told AARP: ‘High doses of steroids can weaken your immune system and possibly reduce the effectiveness of the flu vaccine.’

The CDC says online regarding prednisone’s interaction with other vaccines, including the MMR shot: “A substantially immunosuppressive dose of steroids is considered to be more than two weeks of daily intake of 20 mg or 2 mg/kg body weight of prednisone or equivalent.”

The usual dose strength for prednisone varies between 5 mg and 25 mg for tablets.

Steroid injections

About 9 million people in the U.S. receive steroid injections each year to relieve chronic or long-term pain.

The injections are administered into areas such as the hips, knees and shoulders and work by reducing inflammation in the joint and reducing feelings of pain.

However, research has shown that these injections can affect how the body responds to a flu shot.

The above message from the New York Health Department urged residents to get their flu vaccines

Dr. William Raoofi, a physician at the Center for Interventional Pain Medicine in Maryland, told AARP, “If you get an injected steroid into a joint or epidural space, you get some systemic absorption of the medication, which is a [short-term] weakening of your immune system.

‘If you are then vaccinated and exposed to the weakened flu virus, your immune system does not respond as well to it.’

A Study from 2018 The Mayo Clinic found that 15,000 people found that those who received a steroid injection around the same time as a flu shot had a 52 percent higher risk of infection with the flu compared to those who only received the flu vaccine.

In some cases, patients seeking injections for their pain will have to be turned away if they have recently received a flu shot and will have to wait up to two weeks for the body to fully respond to the vaccine.

Chemotherapy

Chemotherapy drugs are powerful drugs that fight cancer by attacking and destroying rapidly dividing cells in the body.

But they can misfire and attack the immune system, which also contains rapidly dividing cells.

Doctors warn that chemotherapy drugs weaken the immune system, which in turn can make flu vaccinations less effective.

They say patients receiving chemotherapy — which amounts to about 1 million people — should talk to their provider about whether they should also sign up for a flu vaccine.

An earlier study from the NIH suggested that people receiving chemotherapy should get two doses of the flu vaccine each year to be as effective as in someone not fighting the disease, who only needs to get one a year.

Cancer patients are at greater risk of developing complications from the flu, such as pneumonia, because of their weakened immune systems.

One study from 2022 found that cancer patients had a 41 percent higher risk of death from pneumonia compared to those who were cancer-free.

For those whose cancer had spread within their bodies, they were twice as likely to die from pneumonia.

Biological medicines

Cancer patients may also use a type of drug called a biologic.

These are drugs that bind to cancer cells in the body to help the immune system find and destroy cancer.

But this can also damage the immune system, reducing its ability to respond to vaccines and mount a strong immune response.

Doctors say patients taking biologics should consult their healthcare provider about whether they should get a flu shot.

Types of biologics include atezolizumab, or Tecentria, avelumab, or Bavencio, and pembrolizumab, or Keytruda.