COVID-19 vaccines: Get the facts

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

As the coronavirus disease 2019 (COVID-19) pandemic continues, you might have questions about COVID-19 vaccines. Find out about the different types of COVID-19 vaccines, how they work, the possible side effects, and the benefits for you and your family.

COVID-19 vaccine benefits

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

A COVID-19 vaccine might:

  • Protect you from getting COVID-19
  • Prevent you from becoming seriously ill, becoming hospitalized or dying due to COVID-19
  • Limit the spread of COVID-19

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

Getting COVID-19 offers some natural protection or immunity from reinfection with the virus that causes COVID-19. It's estimated that getting COVID-19 and COVID-19 vaccination both result in a low risk of another infection with a similar variant for at least six months.

But 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. The spread of new variants can also increase the risk of reinfection.

In addition, COVID-19 vaccination might offer better protection than getting sick with COVID-19. A recent study showed that unvaccinated people who already had COVID-19 are more than twice as likely as fully vaccinated people to be reinfected with COVID-19.

If you were treated for COVID-19 with monoclonal antibodies or convalescent plasma, there is no need to delay getting a COVID-19 vaccine.

Safety and side effects of COVID-19 vaccines

What COVID-19 vaccines have been authorized or approved?

Because there is an urgent need for COVID-19 vaccines and the Food and Drug Administration's (FDA's) vaccine approval process can take years, the FDA first gave emergency use authorization to COVID-19 vaccines based on less data than is typically required. The data must show that the vaccines are safe and effective before the FDA can give emergency use authorization or approval. Vaccines with FDA emergency use authorization or approval include:

  • Pfizer-BioNTech COVID-19 vaccine. The FDA has approved the Pfizer-BioNTech COVID-19 vaccine, now called Comirnaty, to prevent COVID-19 in people age 12 and older. The FDA approved Comirnaty after data found the vaccine is safe and effective. The Pfizer-BioNTech COVID-19 vaccine is 91% effective in preventing severe illness with COVID-19 in people age 16 and older. The vaccine is 100% effective in preventing COVID-19 in children ages 12 through 15. For people age 12 and older, the Pfizer-BioNTech COVID-19 vaccine involves two shots. The second dose can be given three to eight weeks after the first dose.

    The vaccine is available under an emergency use authorization for children ages 5 through 11. This vaccine is about 91% effective in preventing COVID-19 in children ages 5 through 11. It requires two shots, given three weeks apart. It also contains a lower amount of mRNA than the Pfizer-BioNTech COVID-19 vaccine used for people age 12 and older.

    The vaccine is now also available under an emergency use authorization for children ages 6 months through 4 years old. It requires three shots. The first two shots are given three to eight weeks apart. The third shot is given at least eight weeks after the second shot.

  • Moderna COVID-19 vaccine. The FDA has approved the Moderna COVID-19 vaccine, now called Spikevax, to prevent COVID-19 in people age 18 and older. The Moderna COVID-19 vaccine is 94% effective in preventing COVID-19 with symptoms. It requires two shots. The second dose can be given four to eight weeks after the first dose.

    The vaccine is now also available under an emergency use authorization for children ages 6 months through 17 years old. It requires two shots, given four to eight weeks apart.

  • Janssen/Johnson & Johnson COVID-19 vaccine. This vaccine is available under an emergency use authorization. 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 COVID-19 — at least 28 days after vaccination. It requires one shot. Due to the risk of a potentially life-threatening blood-clotting problem, the FDA is restricting use of the Janssen/Johnson & Johnson vaccine to certain people age 18 and older. Examples include people who had a severe allergic reaction after getting an mRNA COVID-19 vaccine and people who can't get an mRNA COVID-19 vaccine due to limited access or personal or religious concerns. If you get this vaccine, be sure to understand the risks and symptoms of the blood-clotting problem.
  • Novavax COVID-19 vaccine, adjuvanted. This vaccine is available under an emergency use authorization for people age 12 and older. It requires two shots, given three to eight weeks apart. Research done before the spread of the delta and omicron variants has shown that the vaccine is 90% effective at preventing mild, moderate and severe disease with COVID-19. For people age 65 and older, the vaccine is 79% effective.

The shortest interval between the first and second doses of mRNA COVID-19 vaccines is still recommended for people who have weakened immune systems, people age 65 and older and others who need rapid protection due to concern about community transmission or risk of severe illness. An eight-week interval between the first and second doses might be best for some people, especially males ages 12 to 39. A longer interval might increase protection against COVID-19 and reduce the risk of rare heart problems, such as myocarditis and pericarditis.

How do the COVID-19 vaccines work?

Both the Pfizer-BioNTech and the Moderna COVID-19 vaccines use genetically engineered messenger RNA (mRNA). Coronaviruses have a spikelike structure on their surface called an S protein. COVID-19 mRNA vaccines give your cells instructions for how to make a harmless piece of an S protein. After vaccination, your muscle cells begin making the S protein pieces and displaying them on cell surfaces. The immune system recognizes the protein and begins building an immune response and making antibodies. After delivering instructions, the mRNA is immediately broken down. It never enters the nucleus of your cells, where your DNA is kept.

The Janssen/Johnson & Johnson COVID-19 vaccine is a vector vaccine. In this type of vaccine, genetic material from the COVID-19 virus is placed in 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 virus that causes COVID-19, the antibodies will fight the virus.

Viral vector COVID-19 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.

The Novavax COVID-19, adjuvanted vaccine is a protein subunit vaccine. These vaccines include only the parts (proteins) of a virus that best stimulate your immune system. The Novavax COVID-19 vaccine contains harmless S proteins. It also has an ingredient called an adjuvant that helps with your immune system response. Once your immune system recognizes the S proteins, this vaccine creates antibodies and defensive white blood cells. If you later become infected with the COVID-19 virus, the antibodies will fight the virus.

Protein subunit COVID-19 vaccines don’t use any live virus and can’t cause you to become infected with the COVID-19 virus. The protein pieces also don’t enter the nucleus of your cells, where your DNA is kept.

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. As a result, the COVID-19 vaccines can't cause you to become sick with COVID-19 or shed any vaccine parts.

It can 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 general 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

Babies ages 6 months through 3 years old also might cry, feel sleepy or lose their appetite after vaccination.

You'll be monitored for 15 minutes after getting a COVID-19 vaccine to see if you have an allergic reaction.

Most side effects go away in a few days. Side effects after the second dose might be more intense. Many people have no side effects. Side effects of booster shots appear to be similar to side effects experienced after the two-dose or single-dose primary shots.

If the redness or tenderness where the shot was given gets worse after 24 hours or you are concerned about any side effects, contact your doctor.

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 CDC has also created v-safe, a smartphone-based tool that allows users to report COVID-19 vaccine side effects.

If you have additional questions or concerns about your symptoms, talk to your doctor.

Can COVID-19 vaccines affect the heart?

In the U.S., there has been an increase in reported cases of myocarditis and pericarditis after mRNA COVID-19 vaccination, particularly in males ages 12 to 29. Myocarditis is the inflammation of the heart muscle, while pericarditis is the inflammation of the lining outside the heart. These reports are rare.

Of the cases reported, the problem happened more often after the second dose of the COVID-19 vaccine and typically within one week of COVID-19 vaccination. Most of the people who got care felt better after receiving medicine and resting. Research also shows that there’s an increased risk for these conditions after the Novavax COVID-19 vaccine is given.

Symptoms to watch for include:

  • Chest pain
  • Shortness of breath
  • Feelings of having a fast-beating, fluttering or pounding heart

If you or your child has any of these symptoms within a week of getting a COVID-19 vaccine, seek medical care.

If you or your child develops myocarditis or pericarditis after a dose of an mRNA COVID-19 vaccine, the CDC recommends avoiding getting another dose of any COVID-19 vaccine.

What is the connection between the Janssen/Johnson & Johnson COVID-19 vaccine and Guillain-Barre syndrome?

Some people who received the Janssen/Johnson & Johnson COVID-19 vaccine have developed Guillain-Barre syndrome. This is a rare disorder in which your body's immune system attacks your nerves. The chances of this happening are very low.

This disorder is most often reported in men ages 50 to 64. Symptoms most often appeared within 42 days of vaccination. Seek immediate medical care after getting the Janssen/Johnson & Johnson COVID-19 vaccine if you have:

  • Weakness or tingling sensations, especially in the legs or arms, that worsen and spread to other body parts
  • Difficulty walking
  • Difficulty with facial movements, including speaking, chewing or swallowing
  • Double vision or inability to move eyes
  • Difficulty with bladder control or bowel function

What are the symptoms of a blood-clotting reaction to the Janssen/Johnson & Johnson COVID-19 vaccine?

The Janssen/Johnson & Johnson COVID-19 vaccine can cause thrombosis with thrombocytopenia syndrome. This is a blood-clotting problem that can be life-threatening.

As a result, the FDA is restricting use of the Janssen/Johnson & Johnson vaccine to certain people age 18 and older. Examples include people who had a severe allergic reaction after getting an mRNA COVID-19 vaccine and people who can't get an mRNA COVID-19 vaccine due to limited access or personal or religious concerns. Research suggests there isn't an increased risk of this blood-clotting problem after mRNA COVID-19 vaccination.

Serious side effects of the Janssen/Johnson & Johnson COVID-19 vaccine typically happen within two weeks of vaccination and require emergency care. Possible symptoms include:

  • Shortness of breath
  • Persistent stomach pain
  • Severe or persistent headaches or blurred vision
  • Chest pain
  • Leg swelling
  • Easy bruising or tiny red spots on the skin beyond the injection site

This vaccine shouldn't be given to anyone who develops thrombosis with thrombocytopenia after getting the Janssen/Johnson & Johnson COVID-19 vaccine or any other adenovirus vector COVID-19 vaccine.

Variants and COVID-19 vaccines

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

Currently, the CDC has identified one variant of the virus (SARS-CoV-2) that causes coronavirus disease 2019 (COVID-19) as a variant of concern:

  • Omicron. Omicron spreads more easily than the original virus that causes COVID-19 and the delta variant. However, omicron appears to cause less severe disease. People who are fully vaccinated can get breakthrough infections and spread the virus to others. But the COVID-19 vaccines are effective at preventing severe illness. This variant also reduces the effectiveness of some monoclonal antibody treatments. Omicron has a few major offshoots (sublineages), including BA.5 and BA.2.12.1. BA.5 made up about 88% of COVID-19 infections that had genetic sequencing in the U.S. during a recent week in August 2022, according to the CDC.

In April, the CDC downgraded the delta variant from a variant of concern to a variant being monitored. This means that the delta variant isn’t currently considered a major public health threat in the U.S.

Things to know before a COVID-19 vaccine

Are COVID-19 vaccines free?

In the U.S., the federal government is providing COVID-19 vaccines free of charge to all residents, regardless of immigration status or health insurance coverage. The COVID-19 vaccines are free whether offered by a clinic, retail pharmacy or other location.

Can I get a COVID-19 vaccine if I have an existing health condition?

Yes, COVID-19 vaccines are safe for people who have existing health conditions, including conditions that increase the risk of severe illness with COVID-19.

People who have a moderately or severely weakened immune system should get an additional primary shot and a booster shot.

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

Don't take 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.

Allergic reactions and COVID-19 vaccines

What are the signs of an allergic reaction to a COVID-19 vaccine?

You might be having an immediate allergic reaction to a COVID-19 vaccine if you experience these symptoms within four hours of getting vaccinated:

  • Hives
  • Swelling of the lips, eyes or tongue
  • Wheezing

If you have any signs of an allergic reaction, get help right away. Tell your doctor about your reaction, even if it went away on its own or you didn't get emergency care. This reaction might mean you are allergic to the vaccine. You might not be able to get a second dose of the same vaccine. However, you might be able to get a different vaccine for your second dose.

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're typically 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 about getting 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.

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. However, you might be able to get a different vaccine for your second dose.

Pregnancy, breastfeeding and fertility with COVID-19 vaccines

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

If you are pregnant or breastfeeding, it's recommended that you get a COVID-19 vaccine.

The overall risk of COVID-19 to pregnant women is low. However, women who are pregnant or were recently pregnant are at increased risk of severe illness with COVID-19. Pregnant women with COVID-19 are also more likely to deliver a baby before the start of the 37th week of pregnancy (premature birth). They might also be at increased risk of problems such as stillbirth and pregnancy loss.

Getting a COVID-19 vaccine can protect you from severe illness due to COVID-19. Vaccination can also help pregnant women build antibodies that might protect their babies. Research shows that infants born to mothers who receive two doses of an mRNA COVID-19 vaccine — such as the Pfizer-BioNTech or Moderna COVID-19 vaccine — might have a lower risk of hospitalization due to COVID-19 infection in their first six months of life.

COVID-19 vaccines don't cause infection with the virus that causes COVID-19, including in pregnant women or their babies. None of the COVID-19 vaccines contain the live virus that causes COVID-19. Also, keep in mind that mRNA COVID-19 vaccines don't alter your DNA.

Findings from a study of more than 40,000 women show that getting a COVID-19 vaccine during pregnancy poses no serious risks for pregnant women who were vaccinated or their babies. Most of the women in the study received an mRNA vaccine. In addition, vaccines that use the same viral vector as the Janssen/Johnson & Johnson COVID-19 vaccine have been given to pregnant women in each trimester of pregnancy in clinical trials. No harmful effects were found.

Can a COVID-19 vaccine affect fertility or menstruation?

If you are trying to get pregnant or might become pregnant in the near future, it's recommended that you get a COVID-19 vaccine. There is no evidence that any vaccines, including COVID-19 vaccines, cause fertility problems in men or women.

COVID-19 vaccines might affect menstrual cycles. A new survey of more than 39,000 people between ages 18 and 80 showed that 42% of people with regular menstrual cycles had heavier bleeding than usual after vaccination. In contrast, 44% reported no change and 14% had lighter periods than usual. In addition, 71% of people using long-acting reversible contraceptives, 39% of people using gender-affirming hormones and 66% of post-menopausal people reported breakthrough bleeding. All of the people surveyed were fully vaccinated against COVID-19 and, to their knowledge, hadn’t gotten COVID-19 before being vaccinated.

Keep in mind that many things can affect menstrual cycles, including infections, stress, sleep problems, and changes in diet or exercise.

Children and COVID-19 vaccines

What COVID-19 vaccines have been authorized or approved for kids?

In the U.S., COVID-19 vaccines are available to children by age group:

  • Ages 6 months through 4 or 5 years old. The FDA has given emergency use authorization to a Pfizer-BioNTech COVID-19 vaccine for children ages 6 months through 4 years old. This vaccine requires three shots. The first two shots are given three to eight weeks apart. The third shot is given at least eight weeks after the second shot. Research shows that the three shots have produced antibody levels similar to those in young adults after getting the Pfizer-BioNTech vaccine.

    The FDA has also given emergency use authorization to a Moderna COVID-19 vaccine for children ages 6 months through 5 years old. This vaccine requires two shots, given four to eight weeks apart. It’s estimated that this vaccine is about 51% effective in preventing COVID-19 in babies ages 6 months through 23 months. For kids ages 2 through 5 years old, the vaccine is estimated to be 37% effective in preventing COVID-19.

    Both vaccines contain lower amounts of mRNA than the mRNA COVID-19 vaccines for older children and adults.

  • Ages 5 or 6 through 11. The FDA has given emergency use authorization to a Pfizer-BioNTech COVID-19 vaccine for children ages 5 through 11. This vaccine involves two shots, given three weeks apart. Research shows that this vaccine is about 91% effective in preventing COVID-19 in this age group.

    The FDA has also given emergency use authorization to a Moderna COVID-19 vaccine for children ages 6 through 11. This vaccine requires two shots, given four to eight weeks apart. For kids in this age group, the Moderna vaccine causes an immune response similar to that seen in adults.

    Both vaccines contain lower amounts of mRNA than the mRNA COVID-19 vaccines for people age 12 and older.

  • Ages 12 through 17. The FDA has approved the Pfizer-BioNTech COVID-19 vaccine, now called Comirnaty, for people age 12 through 17. This vaccine involves three shots. The first two are given three to eight weeks apart. The third shot, a booster, is given at least two months after the second shot. It contains the same amount of mRNA as the Pfizer-BioNTech COVID-19 vaccine for people age 16 and older. Research has shown that this vaccine is 100% effective in preventing COVID-19 in children ages 12 through 15.

    The FDA has also given emergency use authorization to a Moderna COVID-19 vaccine for children ages 12 through 17. This vaccine requires two shots, given four to eight weeks apart. It contains the same amount of mRNA as the Moderna COVID-19 vaccine for people age 18 and older. For kids ages 12 through 17, the Moderna vaccine causes an immune response similar to that seen in adults.

    The FDA has also given emergency use authorization to a Novavax COVID-19 vaccine for people age 12 and older. This vaccine requires two shots, given three to eight weeks apart. Based on research submitted to the FDA, in children age 12 through 17, this vaccine is about 78% effective in preventing symptomatic COVID-19 illness.

An eight-week interval between the first and second doses might be best for some people, especially males ages 12 to 39. A longer interval might increase protection against COVID-19 and reduce the risk of rare heart problems, such as myocarditis and pericarditis.

Is there any difference in the COVID-19 vaccines for children and adults?

Yes. The Pfizer-BioNTech COVID-19 vaccine for children ages 6 months to 4 years old and the Moderna COVID-19 vaccine for children ages 6 months through 5 years contain lower amounts of mRNA than their COVID-19 vaccines for older children and adults.

The Pfizer-BioNTech COVID-19 vaccine for children ages 5 through 11 and the Moderna COVID-19 vaccine for children ages 6 through 11 also contain lower amounts of mRNA than their COVID-19 vaccines for people age 12 and older.

Smaller needles are also used to deliver the vaccine to the younger children.

If children don't frequently experience severe illness with COVID-19, why do they need a COVID-19 vaccine?

A COVID-19 vaccine can prevent your child from getting COVID-19 and spreading it at home and in school.

If your child gets COVID-19, a COVID-19 vaccine could prevent severe illness.

Getting a COVID-19 vaccine can also help keep your child in school and more safely have play dates and participate in sports and other group activities.

How did the FDA determine the safety and effectiveness of the COVID-19 vaccines for use in kids?

For kids ages 5 through 11, the FDA reviewed a vaccine study of more than 4,600 children in this age range. Of this group, about 3,100 were given the Pfizer-BioNTech COVID-19 vaccine. The other children were given an inactive (placebo) shot. Children who were given the vaccine were monitored for side effects for at least two months after the second dose. Side effects were generally mild to moderate.

The FDA also took an early look at cases of COVID-19 that occurred one week after children were given a second dose of the vaccine. None of the children in this analysis had been previously diagnosed with COVID-19. Among 1,305 children given the vaccine, there were three cases of COVID-19. Among 663 children given the placebo, there were 16 cases of COVID-19. The results suggest that the vaccine is about 91% effective in preventing COVID-19 in this age group.

For kids ages 12 through 15, the FDA reviewed a vaccine study of more than 2,200 U.S. children in this age range. Of this group, about half were given the Pfizer-BioNTech COVID-19 vaccine. The other children were given a placebo shot.

A week after the second dose was given, there were no cases of COVID-19 in the 1,005 children given the Pfizer-BioNTech vaccine. Among 978 children given the placebo, there were 16 cases of COVID-19. None of the children had previously been diagnosed with COVID-19. The results suggest that the vaccine is 100% effective at preventing the COVID-19 virus in this age group.

Also, a portion of the children in each age group were monitored for safety for at least two months after being given the second dose of the COVID-19 vaccine.

To determine the effectiveness of the Pfizer-BioNTech vaccine for kids ages 6 months through 4 and the Moderna COVID-19 vaccine for kids ages 6 months through 17 years old, the FDA looked at the immune responses of children in these age groups after they were fully vaccinated. The FDA compared those responses to the immune responses of young adults who’d been given higher doses of the same mRNA vaccine.

As with the other vaccines, side effects were recorded and a portion of the children were monitored for safety for at least two months after being fully vaccinated.

After a COVID-19 vaccine

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

You are considered fully vaccinated two weeks after you get a second dose of an mRNA COVID-19 vaccine or two weeks after you get a single dose of the Janssen/Johnson & Johnson COVID-19 vaccine. You are considered up to date with your vaccines if you have gotten all recommended COVID-19 vaccines, including booster doses, when you become eligible.

After getting vaccinated, you can more safely return to doing activities that you might not have been able to do because of the pandemic. However, if you're in an area with a high number of people with COVID-19 in the hospital and new COVID-19 cases, the CDC recommends wearing a well-fitted mask indoors in public, whether or not you're vaccinated.

If you have a weakened immune system or have a higher risk of serious illness, wear a mask that provides you with the most protection possible when you're in an area with a high number of people with COVID-19 in the hospital and new COVID-19 cases. Check with your health care provider to see if you should wear a mask when you're in an area with a lower number of new COVID-19 cases and people with COVID-19 in the hospital.

The CDC recommends that you wear a mask on planes, buses, trains and other public transportation traveling to, within or out of the U.S., as well as in places such as airports and train stations.

If you are traveling in the U.S., you don't need to get tested before or after your trip or quarantine after you return. If you are traveling outside of the U.S., you don't need to get tested before you leave the U.S. unless your destination requires it. You no longer need to show a negative test result or proof that you've recovered from COVID-19 in the past three months before boarding an international flight to the U.S.

If you've gotten all recommended vaccine doses, including boosters and additional primary shots, and you've had close contact with someone who has the COVID-19 virus, get tested at least five days after the contact happens.

Can I still get COVID-19 after I'm vaccinated?

COVID-19 vaccination will protect most people from getting sick with COVID-19. But some fully vaccinated people will still get COVID-19. These are called vaccine breakthrough infections.

People with vaccine breakthrough infections can spread COVID-19 to others. However, fully vaccinated people with a breakthrough infection are less likely to have serious illness with COVID-19 than those who are unvaccinated. Even when vaccinated people develop symptoms, they tend to be less severe than those experienced by unvaccinated people.

Are COVID-19 vaccine additional primary shots or boosters recommended?

An additional primary shot of a COVID-19 vaccine is recommended for people who are vaccinated and might not have had a strong enough immune response.

In contrast, a booster dose is recommended for people who are vaccinated and whose immune response weakened over time. Immune response fades naturally over time. It can also happen when the virus that causes COVID-19 changes so the immune system doesn't recognize it as well. Research suggests that getting a booster dose can decrease your risk of infection and severe illness with COVID-19.

The CDC recommends additional primary shots and booster doses of COVID-19 vaccines in specific instances:

  • Additional primary shot. The CDC recommends an additional primary shot of an mRNA COVID-19 vaccine for some people with weakened immune systems, such as those who have had an organ transplant. People with weakened immune systems might not develop enough immunity after vaccination with two doses of an mRNA COVID-19 vaccine or one dose of the Janssen/Johnson & Johnson COVID-19 vaccine. An additional shot using an mRNA COVID-19 vaccine might improve their protection against COVID-19. This recommendation is for people age 5 and older.

    The additional primary shot should be given at least four weeks after a second dose of an mRNA COVID-19 vaccine or one dose of the Janssen/Johnson & Johnson COVID-19 vaccine. The additional primary shot should be the same brand as the other two mRNA COVID-19 vaccine doses that were given. If the brand given isn't known, either brand of mRNA COVID-19 vaccine can be given as a third dose.

  • Booster dose. These recommendations differ by age, what vaccines you have been given and the state of your immune system.

    People age 5 and older who had all recommended doses of the Moderna, Pfizer-BioNTech or Novavax COVID-19 vaccines can get the Pfizer-BioNTech COVID-19 updated, or bivalent booster. This booster is based on the original virus strain and two Omicron strains. Kids age 6 and older can choose between the Pfizer-BioNTech and the Moderna COVID-19 bivalent vaccine booster. People can get the booster shot at least two months after their last shot. People who recently had a positive COVID-19 test may consider waiting three months from when their symptoms started to get the booster.

    If you are age 18 or older, and got the Janssen COVID-19 vaccine, you can get either of the mRNA vaccine bivalent boosters at least two months after your shot. People 18 and older may also get a Novavax booster based on the original virus strain as a first booster at least six months after their last shot.

    Pregnant people can also get a COVID-19 booster dose.

  • Booster doses for people with weakened immune systems. People age 5 and older who have a weakened immune system and have had all recommended doses of the Moderna, Pfizer-BioNTech or Novavax COVID-19 vaccines can get an updated, or bivalent, booster dose of the Pfizer-BioNTech COVID-19 vaccine. The bivalent booster can be given at least two months after the last shot.

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.

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Oct. 26, 2022 See more In-depth

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  2. COVID-19 and vitamin D
  3. Convalescent plasma therapy
  4. Coronavirus disease 2019 (COVID-19)
  5. COVID-19: How can I protect myself?
  6. Cough
  7. Herd immunity and coronavirus
  8. COVID-19 and pets
  9. COVID-19 and your mental health
  10. COVID-19 antibody testing
  11. COVID-19, cold, allergies and the flu
  12. COVID-19 drugs: Are there any that work?
  13. Long-term effects of COVID-19
  14. COVID-19 tests
  15. COVID-19 in babies and children
  16. Coronavirus infection by race
  17. COVID-19 travel advice
  18. COVID-19 vaccine: Should I reschedule my mammogram?
  19. COVID-19 vaccines for kids: What you need to know
  20. COVID-19 variant
  21. COVID-19 vs. flu: Similarities and differences
  22. COVID-19: Who's at higher risk of serious symptoms?
  23. Debunking coronavirus myths
  24. Diarrhea
  25. Different COVID-19 vaccines
  26. Extracorporeal membrane oxygenation (ECMO)
  27. Fever
  28. Fever: First aid
  29. Fever treatment: Quick guide to treating a fever
  30. Fight coronavirus (COVID-19) transmission at home
  31. Honey: An effective cough remedy?
  32. How do COVID-19 antibody tests differ from diagnostic tests?
  33. How to take your pulse
  34. How to measure your respiratory rate
  35. How to take your temperature
  36. How well do face masks protect against COVID-19?
  37. Loss of smell
  38. Mayo Clinic Minute: You're washing your hands all wrong
  39. Mayo Clinic Minute: How dirty are common surfaces?
  40. Multisystem inflammatory syndrome in children (MIS-C)
  41. Nausea and vomiting
  42. Pregnancy and COVID-19
  43. Red eye
  44. Safe outdoor activities during the COVID-19 pandemic
  45. Safety tips for attending school during COVID-19
  46. Sex and COVID-19
  47. Shortness of breath
  48. Thermometers: Understand the options
  49. Treating COVID-19 at home
  50. Unusual symptoms of coronavirus
  51. Vaccine guidance from Mayo Clinic
  52. Watery eyes