HomeHealth TopicVaccines

What’s the Difference Between Antibiotics and Vaccines?

Kerry R. McGee, MD, FAAPSophie Vergnaud, MD
Published on July 1, 2021

Key takeaways:

  • Both vaccines and antibiotics provide strong protection against germs that cause infections.

  • Vaccines strengthen your immune system so infections can’t get started, whereas antibiotics help fight an infection that is already making you sick.

  • Since vaccines and antibiotics do different things, it usually isn’t a problem to use them both at the same time.

A cropped shot of someone with a vaccine bandaid on their arm taking a pill.
Doucefleur/iStock via Getty Images

Infections have always been one of our greatest enemies. Since the beginning of human history, germs that could spread to people, between people, and through communities have been a frightening and deadly reality. 

Recently, the COVID-19 pandemic has reminded us that infections still have the potential to turn our day-to-day lives upside down.

Antibiotics and vaccines are both part of the reason why many scary infections aren’t around now as much as they used to be — and why others are easily treatable. But how do they work together? Keep reading to learn more about the relationship between vaccines and antibiotics.

Antibiotics vs. vaccines: What’s the difference?

If antibiotics are weapons against germs, then vaccines help us build our armor. Both pieces are important — and they both play critical roles in keeping us healthy — but they work in very different ways.

How do vaccines fight infections?

Vaccines help you build a defense against illnesses you could face down the road. We have vaccines against some illnesses caused by bacteria, as well as some caused by viruses.  

When you get a vaccine, your body is introduced to harmless examples of bacteria or viruses. This introduction gives your body a heads-up about germs that could become a threat if you encounter them in the future. Your immune system takes note of these possible intruders, and then is ready to respond quickly if you are exposed to them later.

Once you’re vaccinated, your immune system has “boots on the ground” all over your body — on the surfaces in your mouth, nose, and eyes, inside your stomach and gut, and circulating in your bloodstream — all ready to attack at the first sign of invasion. 

The advance intel a vaccine offers is critical: With it, your immune system can stop an infection so fast, you won’t ever know it happened. 

Remember, though, that vaccines rely on your immune system to build a strong defense, so they work best if you take them while you’re healthy.

How do antibiotics fight infections?

Antibiotics are common medications, but they are also sophisticated weapons that kill or stun bacteria in your body. There are a number of different types, and they work in a variety of ways against different types of bacteria. 

It’s important to know that antibiotics work by killing bacteria, so they’re effective only when you have an infection caused by bacteria in your body. This is different from vaccines, which can shield you from infections caused by bacteria or viruses that you might encounter in the future.

Some antibiotics (for example, penicillin and ciprofloxacin) directly kill bacteria. These are called bactericidal antibiotics. Other antibiotics (such as azithromycin and doxycycline) are bacteriostatic. This means that they slow bacteria down, giving your immune system time to catch up. Either way, antibiotics can stop a bacterial infection from spreading.  

Because antibiotics attack bacteria that are living in your body, they’re most effective when you’re already sick with an infection. 

What about antiseptics? 

Antiseptics are different from antibiotics because they aren’t targeted weapons. Instead, they are harsh chemicals that kill just about everything. Antiseptics are helpful for cleaning surfaces, because they can kill bacteria, viruses, and parasites — but they also harm living cells. For that reason, antiseptics can’t be taken as medication. 

Is it true that some vaccines contain antibiotics?

Confusingly, some vaccines contain tiny amounts of antibiotics — but those antibiotics aren’t there to kill germs in your body. In fact, they’re not even the types of antibiotics that are used to treat infections in humans. 

Instead, antibiotics are sometimes added to vaccines to keep bacteria from living in the vaccine liquid during the manufacturing process. This is the same approach used by food packagers to keep germs out of packaged foods. In either case, bacteria could cause big problems if they snuck into the products during manufacturing. The addition of small amounts of antibiotics to the products keeps this from happening.

The tiny amounts of antibiotics used in vaccines are safe for humans. But they won’t kill many bacteria in your body: The amount is way too small to have any effect on you, or on any bacteria trying to make you sick.

Can vaccines cause antibiotic resistance?

No. Some people might worry about this when they learn about the small amounts of antibiotics found in some vaccines. But vaccines don’t cause antibiotic resistance. Instead, they actually fight it. Here’s why.

Antibiotic resistance happens when bacteria develop a trick to evade an antibiotic, and then pass that trick onto the next generation of bacteria through their genes. But this can occur only when the bacteria can survive and grow in an environment where that antibiotic is common.

This means you have to be taking a good dose of antibiotics, usually for a pretty long time (or on and off over time), for antibiotic resistance to become a problem. 

The amount of antibiotics in a vaccine isn’t enough to bother the bacteria growing inside your body. Plus, since vaccines are spread out over time, bacteria aren’t exposed often enough to be able to develop any tricks.

So, no, the tiny amounts of antibiotics found in some vaccines can’t cause antibiotic resistance. Instead, vaccines play a key role in preventing antibiotic resistance, because they block infections from starting by preventing germ colonies from growing and learning any resistance tricks in the first place.

Antibiotics, vaccines, and COVID-19

Let’s say it’s time for your vaccine, but you’re already on antibiotics for a different infection. It’s reasonable to wonder whether your immune system is up to the challenge of building vaccine-related immune defenses while you’re fighting an infection with antibiotics. But don’t worry: You’ve got this. 

Can I get a vaccine while I’m on antibiotics?

Yes, although you might want to wait a few days.

If you’re taking antibiotics for an illness and you’re scheduled to get a vaccine, you can still get it. But, if you’ve got some flexibility in your schedule, it might make sense to delay the vaccine a little bit. That’s because vaccines can trigger a fever, body aches, or chills, and that’s probably not what you need if you’re already feeling lousy.

Plus, there’s a chance those vaccine side effects could make things confusing. If you get a fever from the vaccine while you’re taking antibiotics, you might wonder whether the antibiotics are working. It could be hard to tell whether you’re recovering from your illness the way you should.

That said, getting a vaccine while you’re on antibiotics isn’t dangerous. The vaccine will still do its job, and so will the antibiotics.

Can I take antibiotics after I get a vaccine?

Yes. If you need antibiotics for a bacterial infection, you should take them. They won’t affect how well the vaccine works.

Can I get a vaccine if I have COVID-19?

Getting vaccinated usually means visiting a healthcare provider or pharmacy. If you have COVID-19, that could put other people at risk of catching it from you. So, although it’s technically fine to get a vaccine — including the COVID-19 vaccine — while you have COVID-19, the Centers for Disease Control and Prevention recommends waiting until you’re no longer contagious.

Do antibiotics work against the coronavirus?

No. The coronavirus is caused by a virus — not by bacteria at all. Viruses don’t live and reproduce independently the way bacteria do. Instead, they hijack your body’s cells and use the machinery there to make copies of themselves. That makes them tough to kill, and antibiotics just won’t do it.

The bottom line

Vaccines strengthen your immune system shield long before you get sick. Antibiotics, on the other hand, are powerful weapons that directly fight against bacteria as they try to invade your body. Although they work very differently, both vaccines and antibiotics have important roles to play when it comes to keeping us safe from infectious diseases.

References

Baquero, F., et al. (2020). Proximate and ultimate causes of the bactericidal action of antibiotics. Nature Reviews Microbiology.

Centers for Disease Control and Prevention. (2020). Possible side effects from vaccines.

View All References (7)

Centers for Disease Control and Prevention. (2021). Interim guidance for routine and influenza immunization services during the COVID-19 pandemic.

Children’s Hospital of Philadelphia. (2019). Vaccine ingredients - antibiotics.

Gavi. (2020). How do vaccines actually work? VaccinesWork.

HealthyChildren.org. (n.d.). Vaccine preventable diseases.

Immunize.org. (2020). Ask the experts: Contraindications and precautions.

Loree, J., et al. (2021). Bacteriostatic antibiotics. StatPearls.

Micoli, F., et al. (2021). The role of vaccines in combatting antimicrobial resistance. Nature Reviews Microbiology.

GoodRx Health has strict sourcing policies and relies on primary sources such as medical organizations, governmental agencies, academic institutions, and peer-reviewed scientific journals. Learn more about how we ensure our content is accurate, thorough, and unbiased by reading our editorial guidelines.

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