COVID-19 vaccines: Get the facts

Looking to get the facts about the new COVID-19 vaccines? Here's what you need to know about the different vaccines and the benefits of getting vaccinated.

Vaccines to prevent coronavirus disease 2019 (COVID-19) are perhaps the best hope for ending the pandemic. But as the U.S. Food and Drug Administration (FDA) continues authorizing emergency use of COVID-19 vaccines, you likely have questions. Find out about the benefits of the COVID-19 vaccines, how they work, the possible side effects and the importance of continuing to take infection prevention steps.

What are the benefits of getting a COVID-19 vaccine?

A COVID-19 vaccine might:

  • Prevent you from getting COVID-19 or from becoming seriously ill or dying due to COVID-19
  • Prevent you from spreading the COVID-19 virus to others
  • Add to the number of people in the community who are protected from getting COVID-19 — making it harder for the disease to spread and contributing to herd immunity
  • Prevent the COVID-19 virus from spreading and replicating, which allows it to mutate and possibly become more resistant to vaccines

What COVID-19 vaccines have been approved and how do they work?

Currently, several COVID-19 vaccines are in clinical trials. The FDA will review the results of these trials before approving COVID-19 vaccines for use. But because there is an urgent need for COVID-19 vaccines and the FDA's vaccine approval process can take months to years, the FDA will first be giving emergency use authorization to COVID-19 vaccines based on less data than is normally required. The data must show that the vaccines are safe and effective before the FDA can give emergency use authorization. Vaccines with FDA emergency use authorization include:

  • Pfizer-BioNTech COVID-19 vaccine. The Pfizer-BioNTech COVID-19 vaccine is 95% effective in preventing the COVID-19 virus with symptoms. This vaccine is for people age 16 and older. It requires two injections given 21 days apart. The second dose can be given up to six weeks after the first dose, if needed.
  • Moderna COVID-19 vaccine. The Moderna COVID-19 vaccine is 94% effective in preventing the COVID-19 virus with symptoms. This vaccine is for people age 18 and older. It requires two injections given 28 days apart. The second dose can be given up to six weeks after the first dose, if needed.
  • Janssen/Johnson & Johnson COVID-19 vaccine. In clinical trials, this vaccine was 66% effective in preventing the COVID-19 virus with symptoms — as of 14 days after vaccination. The vaccine also was 85% effective at preventing severe disease with the COVID-19 virus — at least 28 days after vaccination. This vaccine is for people age 18 and older. It requires one injection.

Both the Pfizer-BioNTech and the Moderna COVID-19 vaccines use messenger RNA (mRNA). Coronaviruses have a spike-like structure on their surface called an S protein. COVID-19 mRNA vaccines give cells instructions for how to make a harmless piece of an S protein. After vaccination, your cells begin making the protein pieces and displaying them on cell surfaces. Your immune system will recognize that the protein doesn't belong there and begin building an immune response and making antibodies.

The Janssen/Johnson & Johnson COVID-19 vaccine is a vector vaccine. In this type of vaccine, genetic material from the COVID-19 virus is inserted into a different kind of weakened live virus, such as an adenovirus. When the weakened virus (viral vector) gets into your cells, it delivers genetic material from the COVID-19 virus that gives your cells instructions to make copies of the S protein. Once your cells display the S proteins on their surfaces, your immune system responds by creating antibodies and defensive white blood cells. If you become infected with the COVID-19 virus, the antibodies will fight the virus.

Viral vector vaccines can't cause you to become infected with the COVID-19 virus or the viral vector virus. Also, the genetic material that's delivered doesn't become part of your DNA.

Are the new COVID-19 vaccines safe?

Andrew Badley, M.D., COVID-19 Research Task Force Chair, Mayo Clinic: The safety of these vaccines has been studied extensively. They've been tested now in about 75,000 patients in total, and the incidence of adverse effects is very, very low.

These vaccines were fast-tracked, but the parts that were fast-tracked were the paperwork; so the administrative approvals, the time to get the funding — those were all fast-tracked. Because these vaccines have such great interest, the time it took to enroll patients was very, very fast. The follow up was as thorough as it is for any vaccine, and we now have months of data on patients who received the vaccine or placebo, and we've compared the incidence of side effects between patients who received the vaccine and placebo, and that incidence of side effects, other than injection site reaction, is no different.

The side effects to the vaccines are very mild. Some of them are quite common. Those include injection site reactions, fevers, chills, and aches and pains. In a very, very small subset of patients — those patients who've had prior allergic reactions — some patients can experience allergic reaction to the vaccine. Right now we believe that number is exceedingly low.

Do the COVID-19 vaccines protect against the COVID-19 variants?

Early research suggests that the Pfizer-BioNTech and Moderna COVID-19 vaccines can provide protection against the COVID-19 variants identified in the U.K. and South Africa. Vaccine manufacturers are also looking into creating booster shots to improve protection against variants.

In clinical trials, the Janssen/Johnson & Johnson COVID-19 vaccine provided protection against severe disease with the COVID-19 virus caused by variants identified in South Africa and Brazil.

Can a COVID-19 vaccine give you COVID-19?

No. The COVID-19 vaccines currently being developed in the U.S. don't use the live virus that causes COVID-19.

Keep in mind that it will take a few weeks for your body to build immunity after getting a COVID-19 vaccination. As a result, it's possible that you could become infected with the virus that causes COVID-19 just before or after being vaccinated.

What are the possible side effects of a COVID-19 vaccine?

A COVID-19 vaccine can cause mild side effects after the first or second dose, including:

  • Pain, redness or swelling where the shot was given
  • Fever
  • Fatigue
  • Headache
  • Muscle pain
  • Chills
  • Joint pain
  • Nausea and vomiting
  • Feeling unwell
  • Swollen lymph nodes

You'll likely be monitored for 15 minutes after getting a COVID-19 vaccine to see if you have an immediate reaction. Most side effects happen within the first three days after vaccination and typically last only one to two days.

A COVID-19 vaccine may cause side effects similar to signs and symptoms of COVID-19. If you've been exposed to COVID-19 and you develop symptoms more than three days after getting vaccinated or the symptoms last more than two days, self-isolate and get tested.

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Is it OK to take an over-the-counter pain medication before or after getting a COVID-19 vaccine?

It isn’t recommended that you take a pain medication before getting a COVID-19 vaccine to prevent possible discomfort. It’s not clear how these medications might impact the effectiveness of the vaccines. However, it’s OK to take this kind of medication after getting a COVID-19 vaccine, as long as you have no other medical reason that would prevent you from taking it.

What are the long-term side effects of the COVID-19 vaccines?

Because COVID-19 vaccines clinical trials only started in the summer of 2020, it’s not yet clear if these vaccines will have long-term side effects. However, vaccines rarely cause long-term side effects.

If you’re concerned, in the U.S., safety data on COVID-19 vaccines will be reported to a national program called the Vaccine Adverse Event Reporting System. This data is available to the public. The Centers for Disease Control and Prevention (CDC) has also created v-safe, a smartphone-based tool that allows users to report COVID-19 vaccine side effects.

How are the COVID-19 vaccines being distributed?

In the U.S., the CDC has recommended that the COVID-19 vaccines first be offered to:

  • Health care personnel
  • Adult residents of long-term care facilities
  • Frontline essential workers, such as first responders and teachers
  • People age 75 and older
  • People ages 65 to 74
  • People ages 16 to 64 with underlying medical conditions
  • Other essential workers, such as people who work in food service and construction

Guidelines for who will be vaccinated first also vary by state in the U.S. Consult your local health department for the latest information on how and when you can receive a vaccine.

Can I get a COVID-19 vaccine if I have a history of allergic reactions?

If you have a history of severe allergic reactions not related to vaccines or injectable medications, you may still get a COVID-19 vaccine. You should be monitored for 30 minutes after getting the vaccine.

If you've had an immediate allergic reaction to other vaccines or injectable medications, ask your doctor if you should get a COVID-19 vaccine. If you’ve ever had an immediate or severe allergic reaction to any ingredient in a COVID-19 vaccine, the CDC recommends not getting that specific vaccine. Also, people who are allergic to polysorbate should not get an mRNA COVID-19 vaccine.

If you have an immediate or severe allergic reaction after getting the first dose of a COVID-19 vaccine, don't get the second dose.

Can I get a COVID-19 vaccine if I have an underlying medical condition?

Yes, if you have an underlying medical condition you can get a COVID-19 vaccine — as long as you haven't had an allergic reaction to a COVID-19 vaccine or any of its ingredients. But there is limited information about the safety of the COVID-19 vaccines in people who have weakened immune systems or autoimmune conditions.

Can pregnant or breastfeeding women get the COVID-19 vaccine?

There is no research on the safety of COVID-19 vaccines in pregnant or breastfeeding women. However, if you are pregnant or breastfeeding and part of a group recommended to get a COVID-19 vaccine, you may choose to get the vaccine. Talk to your health care provider about the risks and benefits.

Is there anyone who should not get a COVID-19 vaccine?

There is no COVID-19 vaccine yet for children under age 16. Several companies have begun enrolling children as young as age 12 in COVID-19 vaccine clinical trials. Studies including younger children have also begun.

Should I get the COVID-19 vaccine even if I've already had COVID-19?

Getting COVID-19 might offer some natural protection or immunity from reinfection with the virus that causes COVID-19. But it's not clear how long this protection lasts. Because reinfection is possible and COVID-19 can cause severe medical complications, it's recommended that people who have already had COVID-19 get a COVID-19 vaccine. If you’ve had COVID-19, you might delay vaccination until 90 days after your diagnosis. Reinfection with the virus that causes COVID-19 is uncommon in the 90 days after you are first infected.

Can I stop taking safety precautions after getting a COVID-19 vaccine?

Experts want to learn more about the protection that a COVID-19 vaccine provides and how long immunity lasts before changing safety recommendations. Factors such as how many people get vaccinated and how the virus is spreading in communities will also affect these recommendations.

In the meantime, the CDC recommends following these precautions for avoiding infection with the COVID-19 virus:

  • Avoid close contact. This means avoiding close contact (within about 6 feet, or 2 meters) with anyone who is sick or has symptoms. Also, keep distance between yourself and others. This is especially important if you have a higher risk of serious illness.
  • Wear cloth face coverings in public places. Cloth face coverings offer extra protection in places such as the grocery store, where it's difficult to avoid close contact with others. Surgical masks may be used if available. N95 respirators should be reserved for health care providers.
  • Practice good hygiene. Wash your hands often with soap and water for at least 20 seconds, or use an alcohol-based hand sanitizer that contains at least 60% alcohol. Cover your mouth and nose with your elbow or a tissue when you cough or sneeze. Throw away the used tissue. Avoid touching your eyes, nose and mouth. Avoid sharing dishes, glasses, bedding and other household items if you're sick. Clean and disinfect high-touch surfaces daily.
  • Stay home if you're sick. Stay home from work, school and public areas if you're sick, unless you're going to get medical care. Avoid public transportation, taxis and ride-sharing if you're sick.

If you have a chronic medical condition and may have a higher risk of serious illness, check with your doctor about other ways to protect yourself.

March 03, 2021 See more In-depth

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