What to know about the COVID-19 vaccine

Vaccines for COVID-19 have prevented millions of hospitalizations and deaths since they first became available in the U.S. in 2020. The vaccine offers your best protection against getting COVID-19, as well developing related complications.

Here is what you need to know about the COVID-19 vaccines, including how safe and effective they are and when to get an updated vaccine.

Who should get the COVID-19 vaccine? What does UChicago Medicine recommend?

COVID-19 vaccination is recommended for:

• All children ages 6 to 23 months
• Children ages 2 to 17 who have at least one underlying risk factor, who have weakened immune systems, who have never been previously vaccinated for COVID-19, who live in congregate settings or live in households with those at risk for severe COVID-19
• Children ages 2 to 17 without underlying risk factors whose parents or guardians want them to get a COVID-19 vaccine
• All pregnant people and those who are planning pregnancy, those who are postpartum (after pregnancy), or during lactation
• All adults 18 years and older

The right time to get a COVID-19 vaccine is whenever you can fit it in. Although the vaccine offers the best protection from contracting COVID-19 in the first 8 to 12 weeks after each dose, it offers ongoing protection against hospitalization and complications. Annual booster doses can help reduce those risks even further.

Who can go to a pharmacy to get the COVID-19 vaccine?

Some pharmacies may have COVID-19 vaccines for children; others may not. If you’re planning on getting children ages 6 months to 11 years old vaccinated at a pharmacy, call ahead to make sure they have the appropriate dosage for your child.

For adults under the age of 65, some pharmacies may require a prescription or other evidence of a qualifying condition. If you are unable to obtain a vaccine through a pharmacy, call your provider.

How effective is the COVID-19 vaccine today?

Like any vaccine, the COVID-19 vaccine teaches your body to recognize specific dangerous pathogens so your immune system is prepared to fight off that infection in the future. The vaccines introduce small parts of germs to your body that are weakened or dead, collectively called antigens. These antigens trigger your body's natural immune response without causing illness.

The vaccine’s effectiveness is a measure of how well it works to prevent illness, infection or severe outcomes caused by exposure to COVID-19. Studies show that for the first few months after your annual COVID-19 vaccine, your likelihood of getting COVID is substantially decreased.

In addition, your likelihood of developing severe disease, ending up in the hospital or dying is significantly lower in the first six months to a year after your immunization. (That’s why it’s important to get a vaccine each year.)

Even if you are at low risk for severe COVID-19, getting vaccinated regularly can decrease the number of times you get infected, how sick you get and how likely you are to spread the virus to other people.

How does COVID-19 spread?

This virus is highly transmissible, and it can spread from person to person — even before someone develops symptoms. It’s carried on respiratory droplets that can land on surfaces or in someone’s mouth or nose when we talk, sneeze or cough. It’s also carried on respiratory aerosols, which can stay in the air and accumulate in rooms with poor ventilation.

The best protection against COVID-19 is avoiding contact with those infected or with COVID symptoms. This can be hard to do, so you should stay updated with your annual COVID-19 vaccine. When COVID-19 is spreading in your community, consider wearing masks indoors and improving ventilation. It’s also a good practice to wash your hands frequently and clean surfaces, even though COVID-19 isn’t likely to spread this way.

Is the COVID-19 vaccine safe?

Yes. Millions of people in the U.S. and globally have received COVID-19 vaccines in the most comprehensive safety monitoring program in U.S. history.

Vaccine trials included a wide range of people. This included people of different ages, races, sexes and health conditions, including HIV, diabetes and lung disease.

Millions of people have received the COVID-19 vaccines since 2020. Evidence shows immunization is both safe and effective. In short, it’s much safer to receive the COVID-19 vaccine than it is to develop COVID-19.

What are the potential vaccine side effects?

All medical treatments have some degree of risk. For vaccines, that risk is typically small. Many vaccines have mild side effects, from soreness at the injection site to a slight fever, body aches and a headache. Side effects typically occur within two days and are entirely over within seven days. Some people have no reactions at all.

It’s important to know that risks reported in connection with the COVID-19 vaccine are significantly lower — and less severe — than risks associated with contracting the virus.

Speak to your primary care physician if you're concerned about the vaccine's safety or have specific health questions.

Can you get a COVID-19 vaccine if you’re pregnant, planning to become pregnant or breastfeeding?

Getting vaccinated can help protect you and your baby from complications due to a severe case of COVID-19 – including delivering a premature or stillborn infant. Newborns whose mothers received a COVID-19 vaccine have better protection against the virus during their first six months. (Children can get a COVID-19 vaccine when they are six months old, but cannot be vaccinated before that.)

Speak to your healthcare provider if you have questions or concerns about vaccination during pregnancy or breastfeeding.

Can you get COVID-19 from the vaccine? Can it cause a false-positive test result?

No, getting COVID-19 from this vaccine is impossible and won’t produce a positive COVID-19 test result. The vaccines aren’t made from the live virus and do not contain the virus that causes COVID-19. Instead, these vaccines typically use a small piece of the virus's genetic material (mRNA) to stimulate an immune response. This response helps your body build immunity to the virus without causing the disease itself.

You may feel unwell after getting vaccinated, but this is a sign of your immune system starting to activate to protect you. However, you could still catch the virus after being immunized and before your body’s immune system has reached its full ability to fight the virus.

Much like the flu vaccine, COVID-19 vaccines are not 100 percent effective, which means there is a chance you could contract COVID-19. However, the COVID-19 vaccine protects you against severity, hospitalization and even death.

If you have been vaccinated and test positive, you should self-isolate, monitor your symptoms and contact your physician.

Will the COVID-19 vaccine alter my DNA? What is an mRNA vaccine?

No, the COVID-19 vaccine will not alter your DNA. It also does not enter the nucleus of your cells. The COVID-19 vaccine is an mRNA vaccine. While this is the first mRNA vaccine, it uses a technology that scientists have been perfecting for decades. (Learn about other types of vaccines.)

In our bodies, our naturally created mRNA – or messenger RNA – delivers recipes to our cells on how to make specific proteins. An mRNA vaccine capitalizes on that process using laboratory-developed mRNA with information on how to defeat a virus. In this case, the COVID-19 vaccine delivers a blueprint to your cells on how to make the spike protein, an essential piece of the COVID-19 virus. This blueprint serves as a wanted ad, telling your body to be on the lookout for the spike protein and to develop an immune response to defeat it. Then, your natural cell processes take over.

The vaccine prepares your body to identify and attack the SARS-CoV-2 virus if it ever enters your system. Within a matter of days, the mRNA from the vaccine is destroyed by your cells, leaving no permanent mark on your body.

Can I still get COVID-19 after being vaccinated?

Yes, it’s still possible for you to contract COVID-19 after receiving the vaccine. No vaccine is 100 percent effective, but the COVID-19 vaccination is your best protection against a severe infection, hospitalization and even death. Getting vaccinated every year helps reduce the number of times you get COVID-19 and the severity of your infections.

I recently had COVID-19. Should I still get the COVID-19 vaccine?

If you’ve had COVID-19 in the past 90 days, you can postpone getting your vaccine until that 90-day window has elapsed. If you are still symptomatic and infectious, you should postpone your vaccine until you are well and no longer contagious.

Otherwise, yes, you should still get the COVID-19 vaccine, even if you’ve had COVID-19.

Who should not get the COVID-19 vaccine?

You should not get the COVID-19 vaccine if you have had a severe allergic reaction to any of the mRNA vaccine ingredients after a previous dose of this vaccine. See the ingredient list here.

You can still get a vaccine if you have a food allergy. Consult your physician if you have any concerns about potential allergic reactions.

You should not get vaccinated if you have a fever on the day of your appointment. Instead, postpone vaccination until your fever subsides.

Do not get vaccinated if you have a confirmed or suspected case of COVID-19. Wait until you recover.

How long will it take for the vaccine to start protecting me?

The vaccine immediately begins teaching your immune system to protect you against COVID-19. However, the time it takes to gain full immunity to the virus will depend on what vaccine you receive. Generally, you should be protected about 14 days after receiving your annual vaccine.

The vaccine is not 100 percent effective against catching COVID. However, the vaccine is your best defense against a severe case, hospitalization and even death.

How many doses of the COVID-19 vaccine do I need?

You should get an updated COVID-19 vaccine every year. People who have preexisting medical conditions, are over the age of 65 or are immunocompromised may be eligible for additional doses. And some children may need two doses if they’ve never been vaccinated.

How long will the vaccine protect me? Will I need to get vaccinated multiple times over my lifetime?

Vaccines for respiratory viruses are notoriously short-acting and the COVID-19 vaccine is proving to be the same. That’s why you should get an updated dose every year. People who have pre-existing medical conditions, are over the age of 65 or are immunocompromised may be eligible for additional doses. The more recent your COVID-19 vaccine, the better protected you are.

Will the current COVID-19 vaccines protect against any new virus strains?

Similar to flu viruses, coronaviruses change slightly over time. Because of how mRNA vaccines are created, scientists can quickly isolate the part of the virus that needs to be recognized by our bodies and produce an effective vaccine.

How much does the COVID-19 vaccine cost?

It depends on the state where you are receiving the vaccine, your insurance and your underlying medical conditions. If you have questions about the cost, ask your physician or pharmacist before receiving the vaccine.

Check with your provider to verify any fees.

Can I still transmit COVID-19 to others after getting the vaccine?

While COVID-19 vaccines have been shown to be highly effective at preventing severe illness, hospitalization and death from COVID-19, it is still possible for vaccinated individuals to contract and transmit the virus to others. However, the risk is significantly reduced compared to unvaccinated individuals.

If you have COVID-19, stay home for at least three days or until your fever is gone without taking medications to reduce the fever (like Tylenol, ibuprofen or aspirin).

Once you are feeling better and no longer have a fever, you may return to work or school, but you should wear a mask around others for at least seven days (longer if you are immunocompromised). If you have any of the conditions associated a with higher risk of complications, talk to your doctor about treatment for COVID-19.

Can COVID-19 vaccines cause heart problems?

Myocarditis, an inflammation of the heart, has been reported in rare instances after receiving the COVID-19 vaccination. This is slightly more common in adolescent and young adult males. Vaccine-related myocarditis is almost always treatable with anti-inflammatory medications and patients recover quickly.

Studies have found that myocarditis is also a common complication of COVID-19. However, COVID-19-associated myocarditis is more common, more severe and harder to treat than vaccine-related cases. In short, you’re more likely to develop myocarditis from COVID-19 than you are from getting the COVID-19 vaccine.

Can you get the COVID-19 vaccine at the same time as your flu shot or RSV shot?

It’s okay to schedule your updated annual COVID-19 vaccine together with the annual flu shot and the RSV shot. You might have a little soreness in both arms, and there’s a slightly higher chance of feeling fatigue and a low fever from getting multiple shots together. But convenience outweighs the risk for most people.

However, if you typically have side effects from vaccines, you may want to space these out one to two weeks apart.

Will the COVID-19 vaccine protect me from getting long COVID?

We know people who have been vaccinated are less likely to develop long COVID complications. However, it’s important to know that a vaccine is just one precaution you’ll need to keep yourself safe. That’s because an immunization alone won’t protect you from long COVID.

We recommend everyone avoid infection as best you can. And if you do contract COVID-19, take steps to shorten your illness by getting appropriate medication from your physician. Those are critical things you should do in addition to getting your annual vaccine.