Do Covid-19 Vaccines Interfere with Common Prescription Drugs?

By Dena Bunis, AARP, Updated February 25, 2021

Medical experts explain why there's little reason to worry about your medications.

Every morning, you take a pill for your blood pressure or diabetes, and then maybe at night, you take a statin for your cholesterol. Now, because of the pandemic, you're being asked to throw a coronavirus vaccination into the mix. While you should consult your doctor if you have concerns, medical experts say the vast majority of prescription drugs will work just as well after you get a COVID-19 vaccine, and they won't diminish the effectiveness of the shot you're getting to ward off the coronavirus.

How can doctors be so sure? It comes down to the fact that most of the maintenance medications we take go nowhere near the system in your body that the COVID-19 vaccines affect: your immune system.

The way the currently available vaccines work is that they expose a person's body to a small protein from the coronavirus that induces the immune system to start fighting the virus, as if the person had been fully infected, explains Adam Berman, M.D., an emergency medicine physician and associate chair of the emergency department at Long Island Jewish Medical Center in New York. The hope is that if your body learns to fight the coronavirus when you aren't infected, then later, if you are, it will be able to protect you by fighting off the infection extremely quickly.

Essentially, the vaccine makes a beeline for your immune system, and “the vast, vast majority of medications that patients take do not affect their immune systems,” says Berman.

For example, the statin you take to guard against high cholesterol interrupts your cholesterol production and has nothing to do with your immune system, says William Schaffner, M.D., an epidemiologist and professor of preventive medicine and health policy at Vanderbilt University. Blood thinners like Warfarin or Eliquis work on your body's blood clotting mechanism. Medicines to control diabetes, like Metformin, work on your glucose metabolism — again, nothing to do with your immune system.

Some medicines may dampen vaccine effectiveness

As with most rules of medical science, there are some exceptions. If you happen to be taking prescription drugs that do affect your immune system, the vaccine might not be as effective as it would be if you weren't.

So if you have had an organ transplant and are taking immunosuppressant drugs or taking those drugs to treat an autoimmune disease, or if you're taking certain cancer chemotherapies, the “immunosuppressive drug could decrease the efficacy of the vaccine,” says William Moss, M.D., executive director of the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health. Same goes for people who are HIV positive and take one or more medications that affect their immune systems.

Even so, Schaffner emphasizes, such medications will continue to work on the conditions you're taking them for — and so will the COVID-19 vaccine.

"Should you still get the vaccines?” asks Schaffner, referring to the currently available COVID-19 vaccines from Pfizer-BioNTech and Moderna. “Absolutely. Now, can we guarantee that you will have 95 percent protection? No, but you will get some degree of protection. And some is better than nothing."

Moss suggests that people think of the COVID vaccines in much the same way they do their annual flu shot or a shingles or pneumonia vaccine. The COVID vaccine “is a new type of vaccine, but fundamentally, it's just a vaccine. It is like other vaccines that basically affect our immune system. And there's no reason to have concerns about how that might interact with other medicines."

Blood Thinners

If you are taking a blood thinner, the Food and Drug Administration (FDA) recommends informing your vaccine provider when you go in for your COVID-19 shot. Blood thinners prevent clotting, so even a small injury such as a needle piercing the skin can cause more bleeding or bruising than usual.

Neither the FDA nor the Centers for Disease Control and Prevention (CDC) say you shouldn’t receive a coronavirus vaccination just because you are on a blood thinner.

Stephen Moll, a professor of medicine at the University of North Carolina (UNC) and the medical director of Clot Connect at the UNC Blood Research Center, reiterates in a January blog post that people on blood thinners should get the COVID-19 vaccine. If you are taking a blood thinner, like warfarin, Eliquis, Pradaxa, Savaysa, Xarelto, Lovenox, Arixtra or another antiplatelet drugs, here are some things to watch for, he says:

• You probably will have a higher risk of bruising at the injection site.

• Keep pressure on the site of the injection for at least five minutes to reduce the risk of bruising.

• The smallest possible needle should be used. Ask for a 25-gauge size needle.

• Consider skipping one dose of your blood thinner, but be sure to check with your doctor before doing so.