COVID-19 Vaccine Safety and Effectiveness

This page is no longer updated and will be removed in June 2023. For updated COVID-19 information and health materials, please go to our COVID-19 Vaccine page.

Four COVID-19 vaccines are authorized for emergency use or fully approved by the U.S. Food & Drug Administration (FDA). These vaccines were shown to be safe and effective in clinical trials. They were developed, tested and authorized using the same rigorous process used for other successful vaccines.

These vaccines also passed independent review by medical experts in the Scientific Safety Review Workgroup, as part of the Western States Pact (English only). See our FAQs for more information.

The Centers for Disease Control and Prevention (CDC) and Washington State Department of Health (DOH) recommend eligible individuals choose to get an mRNA COVID-19 vaccine (Pfizer or Moderna) instead of the Johnson & Johnson (J&J) vaccine due to the rare risk of thrombosis with thrombocytopenia syndrome (TTS), which involves blood clots and a low blood platelet count, and Guillain-Barré syndrome, which is an autoimmune disorder that can damage nerves. The J&J vaccine is still available, and you can talk to your health care provider about your options if you would like to receive it.

Data show the COVID-19 vaccines are safe, and serious side effects are rare.

Video thumbnail - How are COVID-19 vaccines being made?

How COVID Vaccines Are Made

How Can Vaccine and Antibody Studies Move So Quickly and Still Be Safe?

About the COVID-19 Vaccines

The COVID-19 vaccines can protect you in several key ways:

They can greatly reduce your chance of getting seriously ill if you get COVID-19
Completing the vaccine series reduces your chances of hospitalization and lowers your risk of dying from COVID-19
They add to the number of people in the community who are protected from getting COVID-19, making it harder for the disease to spread

Experts continue to conduct more studies about the ability of the vaccine to keep people from spreading the virus to others. Once you are fully vaccinated, it is still possible to get COVID-19, but it's a much smaller chance than if you weren't vaccinated. You're also very unlikely to get really sick or need to go to the hospital.

Pfizer-BioNTech COVID-19 Vaccine

This vaccine is available for youth 6 months through 11 years old under an Emergency Use Authorization (EUA), and fully approved for people 12 years and older (under the name Comirnaty).

In Pfizer-BioNTech Vaccine Trials (U.S. Trial Data)

The clinical trials showed no major unanticipated adverse events:

10% of participants identified as Black/African American
13% of participants identified as Hispanic/Latinx
6% identified as Asian
1.3% identified as Native American
69.7% identified as White

Children ages 6 months-4 years

Approximately 4,500 children 6 months to 4 years participated in clinical trials for the Pfizer COVID-19 vaccine. The immune response of this age group to a 3-dose series was similar to the immune response of older participants. No serious side effects have been detected in the study, which is ongoing

Children ages 5-11

Approximately 3,100 children ages 5 through 11 received the Pfizer COVID-19 vaccine in clinical trials. No serious side effects have been detected in the study, which is ongoing.
The immune responses of children ages 5 through 11 were comparable to those of individuals ages 16 through 25 years of age.
The vaccine was nearly 91% effective in preventing COVID-19 in children 5 through 11.

Children ages 12-15

2,260 participants ages 12 through 15 years old enrolled in an ongoing clinical trial in the United States.
Of these, 1,131 adolescent participants received the vaccine and 1,129 received a placebo. More than half of the participants were followed for safety for at least two months following the second dose.

Moderna COVID-19 Vaccine

This vaccine is fully approved for individuals 18 years and older (under the name Spikevax) and is available under an EUA for individuals ages 6 months through 17 years old.

In Moderna Vaccine Clinical Trials (U.S. Trial Data)

The clinical trials showed no major unanticipated adverse events:

10% of participants identified as Black/African American
20% identified as Hispanic/Latinx
4% identified as Asian
3% identified as “of other descent”
63% identified as White

Children ages 6 months-5 years

Approximately 6,300 participants 6 months to under 6 years participated in a clinical trial for the Moderna COVID-19 vaccine. The vaccine was 50% effective in preventing COVID-19 in this age group. No serious side effects have been detected in the study, which is ongoing.

Children ages 6-11

Approximately 4,000 participants 6-11 years participated in a clinical trial for the Moderna COVID-19 vaccine. The immune response of this age group to the vaccine was comparable to the immune response of the adults. No serious side effects have been detected in the study, which is ongoing.

Children ages 12-17

Approximately 3,700 participants 12-17 years participated in a clinical trial for the Moderna COVID-19 vaccine. The vaccine was 93% effective in preventing COVID-19 among this group. No serious side effects have been detected in the study, which is ongoing.

Novavax COVID-19 Vaccine

This vaccine is authorized for emergency use in individuals 12 years and older.

In Novavax Vaccine Clinical Trials (U.S. Trial Data)

The clinical trials showed no major unanticipated adverse events:

21.5% were Hispanic or Latino
75.9% were White
11.0% were Black or African American
6.2% were American Indian or Alaska Native
4.4% were Asian
1.7% were multiracial

Approximately 30,000 participants 18 years and older participated in a clinical trial for the Novavax COVID-19 vaccine. The vaccine was 90% effective in preventing COVID-19 among this group. No serious side effects have been detected in the study, which is ongoing.

Children ages 12 -17

The 12 – 17 clinical trials showed no major unanticipated adverse events.

Approximately 2,200 participants 12-17 years participated in a clinical trials for the Novavax COVID-19 vaccine. The vaccine was 78% effective in preventing COVID-19 among this group. No serious side effects have been detected in the study, which is ongoing.

Johnson & Johnson – Janssen COVID-19 Vaccine

This vaccine is authorized for emergency use in individuals 18 years and older. This is a single dose (one shot) vaccine.

CDC DOH recommend people 18 years and older choose to get an mRNA COVID-19 vaccine (Pfizer or Moderna) instead of the Johnson & Johnson (J&J) vaccine. The J&J vaccine is still available for limited purposes, and you can talk to your health care provider about your options if you would like to receive it.

In Johnson & Johnson Vaccine Clinical Trials (Global Trial Data)

The clinical trials showed no major unanticipated adverse events:

17% of participants identified as Black/African American
3.5% identified as Asian
8.4% identified as American Indian or Alaska Native
0.25% identified as Native Hawaiian or other Pacific Islander
8.6% identified with multiple races, or race was unknown or not reported
62% identified as White

In addition, about 45% of all participants identified as Hispanic/Latino.

Learn More

Vaccine Safety is Top Priority

As more COVID-19 vaccines are developed, safety remains the top priority. DOH is committed to science and critically evaluating these new vaccines for safety and efficacy in an unbiased way before their use. We are watching the FDA approval process closely to make sure it is thorough and transparent.

Safety and Effectiveness Frequently Asked Questions

What does it mean when a vaccine is fully licensed?

For full approval, the FDA evaluates data over a longer period of time than for an emergency use authorization. For the vaccine to be given full approval, the data must show a high level of safety, effectiveness, and quality control in vaccine production. The purpose of emergency use authorization is to ensure that people can get lifesaving vaccines prior to a longer-term analysis of data. However, EUA still requires a very thorough review of clinical data—just over a shorter period of time.

How do we know the vaccines are safe?

To make sure that COVID-19 vaccines are safe, CDC expanded and strengthened the country’s ability to monitor vaccine safety. As a result, vaccine safety experts can monitor and detect issues that may not have been seen during the COVID-19 vaccine clinical trials.

How will a COVID-19 vaccine work in my body?

The COVID-19 vaccine teaches your immune system to recognize the coronavirus. When you get the vaccine, your immune system makes antibodies (“fighter cells”) that stay in your blood and protect you in case you are infected with the virus. You get protection against the disease without having to get sick.

When enough people in the community can fight off the coronavirus, it has nowhere to go. This means we can stop the spread quicker and get a little closer to ending this pandemic.

Watch this video on how vaccines work in your body.

How are COVID-19 vaccines made?

This short video explains how COVID vaccines are made.

What is an mRNA vaccine?

A messenger RNA, or mRNA vaccine is a new type of vaccine. mRNA vaccines teach your cells how to make a harmless piece of the “spike protein.” The spike protein is what you see on the surface of the coronavirus. Your immune system sees that the protein doesn't belong there, and your body will start to build an immune response and make antibodies. This is similar to what happens when we “naturally” get a COVID-19 infection. Once it does its job, the mRNA quickly breaks down and the body clears it away in a few days.

Although we have used mRNA for other types of medical and veterinary care in the past, creating vaccines using this method is a huge leap forward in science and may mean future vaccines can be created more easily.

You may read more about how mRNA vaccines work on CDC's website, or watch this video from Dr. Paul Offit at the Children's Hospital of Philadelphia.

What is a viral vector vaccine?

This type of vaccine uses a weakened version of a different virus (the “vector”) that gives your cells instructions. The vector enters a cell and uses the cell's machinery to create a harmless piece of the COVID-19 spike protein. The cell displays the spike protein on its surface, and your immune system sees that it doesn't belong there. Your immune system will start to make antibodies and activate other immune cells to fight off what it thinks is an infection. Your body learns how to protect you against future infection with COVID-19, without you having to get sick.

What is a protein subunit vaccine?

Protein subunit vaccines contain pieces of the virus (proteins) that causes COVID-19 (made without using any live virus) with an additive intended to help the vaccine work better in the body. Once your immune system knows how to respond to the spike protein, it will then be able to respond quickly to the actual virus and protect you against COVID-19. Subunit vaccines cannot cause infection with the virus that causes COVID-19 and do not interact with our DNA.

What is an adjuvant?

The adjuvant in the Novavax is the additive intended to help strengthen the body’s immune response.

What types of symptoms are normal after receiving the vaccine?

Like other routine vaccines, the most common side effects are a sore arm, fatigue, headache, and muscle pain.

These symptoms are a sign that the vaccine is working. In the Pfizer, Moderna and Novavax trials, these side effects occurred most often within two days of getting the vaccine, and lasted about a day. Side effects were more common after the second dose (of the initial two-dose series) than the first dose. In the Johnson & Johnson clinical trials, side effects lasted an average of one to two days. For all three vaccines, people over age 55 were less likely to report side effects than younger people.

You may see some rumors about untrue side effects online or on social media. Make sure any time you see a claim about a side effect that you check the source of that claim. This video can teach you more about how to figure out if a claim online is true or not.

What ingredients are in the vaccines?

The ingredients in the COVID-19 vaccines are pretty typical for vaccines. They contain the active ingredient of mRNA or modified adenovirus along with other ingredients like fats, salts, and sugars that protect the active ingredient, help it work better in the body, and protect the vaccine during storage and transport.

The Novavax COVID-19 vaccine is a protein subunit-based vaccine that contains an additive, along with fats and sugars to help the vaccine work better in the body. This vaccine does not use mRNA.

Pfizer, Moderna, Novavax and Johnson and Johnson vaccines do not contain human cells (including fetal cells), the COVID-19 virus, latex, preservatives, or any animal by-products including pork products or gelatin. The vaccines are not grown in eggs and do not contain any egg products.

See this Q&A; webpage from the Children's Hospital of Philadelphia for more information about ingredients. You can also find the full ingredients lists in the Pfizer, Moderna, Novavax and Johnson & Johnson fact sheets.

Does the Johnson & Johnson vaccine contain fetal tissue?

The Johnson & Johnson COVID-19 vaccine was created using the same technology as many other vaccines. It does not contain parts of fetuses or fetal cells.

In this video, Dr. Paul Offit addresses fetal cells and COVID-19 vaccines:

Can I get the COVID-19 vaccine if I'm pregnant, lactating or planning to become pregnant?

Yes, data show that COVID-19 vaccines are safe during pregnancy. The Centers for Disease Control and Prevention (CDC), American College of Obstetricians and Gynecologists (ACOG), and Society for Maternal-Fetal Medicine (SMFM) recommend the COVID-19 vaccine for people who are pregnant, lactating, or planning to get pregnant.

Some studies show that if you are vaccinated, your baby may even get antibodies against COVID-19 through pregnancy and lactation. Unvaccinated pregnant people who get COVID-19 are at increased risk of severe complications like preterm birth or stillbirth. In addition, people who get COVID-19 while pregnant are two to three times more likely to need advanced life support and a breathing tube.

For more resources about getting the COVID-19 vaccine while pregnant and breastfeeding, please see up to date information on the One Vax, Two Lives website.

What is an Emergency Use Authorization (EUA)?

An EUA allows the FDA to make a product available during a declared state of emergency before it has a full license. Any EUA granted by the FDA is further vetted by the Scientific Safety Review Workgroup, as part of the Western States Pact.

What is the Western States Pact?

In October, 2020 Washington joined Oregon, Nevada, Colorado and California to form the Western States Scientific Safety Review Workgroup (Western States Pact) to review the safety and efficacy of COVID-19 vaccines after they were authorized by the FDA. This workgroup provided another layer of expert review around vaccine safety.

The panel included experts appointed by all member states, and nationally recognized scientists with expertise in immunization and public health. To act in close coordination and collaboration with Western states when COVID-19 was declared a health emergency, this panel reviewed all publicly available data concurrently with federal reviews for the four vaccines we currently have available in Washington state. As we move into a new recovery phase of the pandemic, the Western States Pact has disbanded and all vaccine use authorization in western states will be determined by the FDA and vaccine recommendations will come from the CDC.

Read the findings of the Western States Scientific Safety Review Workgroup:

Is it COVID-19 or a vaccine reaction?

After getting a COVID-19 vaccine, you may have some side effects. These are normal signs that your body is building protection against COVID-19. Your arm may hurt where you got your shot, or you may have redness or swelling. You may be tired or have a headache, muscle pain, chills, fever, or nausea. They may affect your ability to do daily activities but should go away in a few days. Some people have no side effects. Learn more about possible side effects after getting a COVID-19 vaccine.

If the symptoms do not go away after a few days, you should seek medical advice. If there’s a possibility you have COVID-19 or were exposed, please stay away from others as a precaution. If you experience a medical emergency after getting the COVID-19 vaccine, call 9-1-1 immediately.

Can I get the COVID-19 vaccine if I've had an allergic reaction to a vaccine in the past?

The vaccine should not be given to people with a known history of severe allergic reaction, such as anaphylaxis, to a previous dose of an mRNA or viral vector vaccine, or to any ingredient of the Pfizer-BioNTech/Comirnaty, Moderna/Spikevax, Novavax or Johnson & Johnson–Janssen COVID-19 vaccines.

People who have had a severe allergic reaction to other vaccines or injectable therapies may still be able to receive the vaccine. However, providers should do a risk assessment and counsel them about potential risks. If the patient decides to get the vaccine, the provider should consider observing them for 30 minutes to monitor for any immediate reactions.

The Advisory Committee on Immunization Practices (ACIP) recommends that providers consider observing all other patients for at least 15 minutes after receiving the vaccine to monitor for an allergic reaction. See ACIP's interim clinical considerations for vaccines for more information.

What happens if I get sick after getting the COVID-19 vaccine?

It's normal to have some side effects after getting the vaccine. This can be a sign that the vaccine is working. If you experience a medical emergency after getting the COVID-19 vaccine, call 9-1-1 immediately.

If you get sick after getting the vaccine, you should report the adverse event to the Vaccine Adverse Event Reporting System (VAERS). An “adverse event” is any health problem or side effect that happens after a vaccination.

For more information about VAERS, see "What is VAERS?" below.

What is VAERS?

VAERS is an early warning system led by the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA). VAERS can help detect problems that may be related to a vaccine.

Anyone (health care provider, patient, caregiver) can report possible adverse reactions to VAERS.

There are limits to the system. A VAERS report does not mean the vaccine caused the reaction or outcome. It only means that the vaccination happened first.

VAERS is set up to help scientists notice trends or reasons they should investigate a possible problem. It is not a list of verified outcomes of vaccination.

When you make a report to VAERS, you help the CDC and the FDA identify possible health concerns and make sure vaccines are safe. If any issues arise, they will take action and notify health care providers about potential issues.

What is a COVID-19 variant?

Viruses mutate (change) as they spread from person to person. A ‘variant' is a mutated strain of virus. Some variants disappear over time and some continue to spread in communities.

The Centers for Disease Control and Prevention (CDC) identifies the virus variants that are concerning. Currently, several variants are concerning because they spread quickly and more easily, causing more COVID-19 infections.

Does the COVID-19 vaccine work against variant strains?

COVID-19 vaccines are working well to prevent severe illness, hospitalization, and death, even against variants. However, public health experts are seeing reduced protection against mild and moderate COVID-19 illness, especially among-high risk populations.

The updated boosters were created to help boost immunity and provide better protection from the omicron variant. It's important to get all recommended doses available for the best protection.

Vaccination is the best way to protect you, your loved ones, and your community. High vaccination coverage will reduce the spread of the virus and help prevent new virus variants from emerging.

Visit our pages on the COVID-19 variants and vaccine breakthrough for more information.

Why should I get the COVID-19 vaccine if most people survive having the disease?

Death is not the only risk from having COVID-19. Many people who get COVID-19 only have mild symptoms. However, the virus is extremely unpredictable, and we know some COVID-19 variants are more likely to make you really sick. Some people can get very sick or die from COVID-19, even young people with no chronic health conditions. Others, known as “COVID long-haulers” may get symptoms that last for months and affect their quality of life. We also don't know yet all the long-term effects of COVID-19 since it's a new virus. Getting vaccinated is our best protection against the virus. Even if you're young and healthy, you should get a COVID-19 vaccine.

If I get a COVID-19 vaccine, do I still need to take other precautions?

Yes, even if you get vaccinated, you may be required to wear a mask in some public indoor settings. Find more information on our Masks and Face Coverings FAQ page. We also recommend you wash your hands often, stay six feet apart, and limit gatherings.

The COVID-19 vaccines work well, but they are not 100% effective. Some people may get COVID-19 even if they've been vaccinated. With the rise of more transmissible variants, it's important that all people take precautions such as wearing masks to reduce transmission of the virus.

What is the difference between vaccination and immunity?

Natural immunity from infection does offer some level of immunity against reinfection but it is important to stress that initial infection among unvaccinated persons increases risk for serious illness, hospitalization, and death. While some people may develop antibodies after COVID-19 infection, others may not. For those that develop some immunity after infection, there is no way to tell how strong that protection is, how long it will last or even which variant the immunity is for.

Because we cannot rely on natural immunity to prevent reinfection or severe illness from COVID-19, being up to date on vaccination remains the best protection and primary strategy to prevent SARS-COV-2 infections, associated complications, and onward transmission.

For more information on immunity and COVID-19, please review these helpful resources.