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Updated on February 6, 2020 at 8:45 pm
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Section 1: COVID-19 vaccine development and safety

The Food and Drug Administration (FDA) has authorized the emergency use of the first COVID-19 vaccines. Multiple other vaccines are under development and several are in large scale clinical trials with tens of thousands of volunteers to ensure they are both safe and effective.

Very limited quantities of COVID-19 vaccines started to arrive in Washington state at the end of 2020. We expect supplies to increase gradually and COVID-19 vaccines should be more widely available to anyone who wants to be vaccinated in spring or summer 2021.

The Food and Drug Administration (FDA) uses Emergency Use Authorizations, known as EUAs, during national emergencies to make a product available to address an urgent health need. The EUA allows a product to be used before it has a full license.

An EUA can be used for tests, devices, or treatments. The FDA has issued EUAs to address anthrax, Ebola, H1N1 and other health emergencies in the past.

FDA guidelines must be met for a COVID-19 vaccine to be considered for an EUA, including safety and effectiveness standards and review by independent medical experts.

If the FDA approves a vaccine for an EUA, a second independent advisory committee will evaluate the safety and effectiveness data. This committee, the Advisory Committee on Immunization Practices (ACIP), will then make a recommendation about whether the vaccine should be used. If they recommend it, ACIP will issue guidelines for healthcare providers.

The FDA and CDC will continue to monitor a vaccine’s safety and effectiveness even after it is approved.

Vaccine safety is a priority. All COVID-19 vaccines must go through a rigorous and multi-step testing and evaluation process before they can be used in the U.S. These include studies with tens of thousands of people and data review by independent safety monitoring boards. They will only be approved or authorized for use if they pass safety and effectiveness standards. Vaccines will also be monitored for safety once they are given.

This short video from the CDC explains more about how COVID-19 vaccines are made:

Usually, vaccine testing and production are done in multiple, time-consuming, separate steps over several years. Because of the pandemic, the federal government provided special funding to vaccine researchers and manufacturers to allow development, testing and production to happen at the same time. No steps are skipped but the timeline for development can go faster.

The two vaccines that have been authorized from Pfizer and Moderna are mRNA vaccines. mRNA vaccine technology has been studied and worked with for decades. Interest has grown in these vaccines because they can be developed in a laboratory using readily available materials. This means the process can be standardized and scaled up, making vaccine development faster than traditional methods of making vaccines.

When a vaccine is authorized by EUA, volunteers who get the COVID-19 vaccine are monitored for a shorter time than with the traditional vaccine approval process. Testing for any COVID-19 vaccine involves thousands of volunteers, and at least half of the volunteers are followed for at least 2 months after their last vaccine dose (rather than the 6 or more months in a traditional process). However, by two months, most side effects from vaccines are expected to surface.

It is possible that rare side effects may only be seen when millions of people are vaccinated. For this reason, the safety of COVID-19 vaccines will continue to be monitored after they are given.

This video from the WA Department of Health offers advice to consider the tone, author, and sources when you see new information, and to check with people you know. Public Health has also developed a resource called Is it True? to discuss some common misinformation about COVID-19 vaccine (to be posted online soon).

Section 2: How COVID-19 vaccine works

COVID-19 vaccines help our bodies develop immunity to the virus that causes COVID-19 without us having to get the illness. When you get the vaccine, your immune system makes antibodies and other infection-fighting cells that protect you in case you are infected with the virus.

Watch a short video from the WA State Dept. of Health that explains more about how COVID-19 vaccines work in your body:

COVID-19 vaccination will help you from getting sick or seriously ill with COVID-19.

  • It helps protect you by teaching your body’s immune system to fight the virus without having to experience a COVID-19 infection.
  • In the clinical trials, the COVID-19 vaccines that are currently available were found to be highly effective in protecting people from COVID-19.

COVID-19 vaccine will be an important tool to help stop the pandemic.

  • Getting vaccinated will help to protect you, your friends and family, and other people in the community from COVID-19. The combination of getting vaccinated and following public health recommendations will offer the best protection from COVID-19 at this time.
  • Wearing masks and social distancing help reduce your chance of being exposed to the virus or spreading it to others, but these measures alone are not enough. Vaccines will work with your immune system so it will be ready to fight the virus if you are exposed.
  • Over time, as more people are vaccinated, we may no longer need some of the other COVID-19 prevention measures that are necessary at this time.

No, COVID-19 vaccines cannot cause COVID-19 infection. COVID-19 vaccines teach our bodies to protect us by making antibodies and other infection-fighting cells, In the case of mRNA vaccines (like the Pfizer and Moderna vaccines), they protect by instructing our own cells to produce a protein that can teach the immune system to prevent COVID-19 illness without using any part of the COVID-19 virus at all.

It’s possible to get side effects like headache, a sore arm, fatigue or a fever in the day or two after you get the shot. But these side effects are short-lived and are signs that the vaccine is building immunity in the body. Some of these side effects may be similar to the symptoms of COVID-19, but it is not the same as an infection. The vaccine does not contain a virus or any part of a virus and cannot cause COVID-19.

The two vaccines that have been authorized from Pfizer and Moderna are mRNA vaccines. mRNA vaccine technology has been studied and worked with for decades.

There is no virus in the mRNA vaccines, so you cannot get a COVID-19 infection from the vaccine. Instead, mRNA vaccines give our cells instructions to make a harmless protein—one that looks just like an important protein on the COVID-19 virus. When your cells make that protein, your body creates a strong immune response and antibodies to protect against COVID-19. Your body learns how to protect you from getting infected without exposure to the virus.

After the mRNA teaches our cells to protect against COVID-19, our body’s enzymes quickly break down and eliminate the mRNA. mRNA does not get into the nucleus of our cells, DNA, or genetic material.

Although these are the first mRNA vaccines to be authorized for use, mRNA technology has been studied for more than 30 years. More information about how mRNA vaccines work can be found on the CDC’s website.

The key ingredient in both the Pfizer and Moderna vaccines is mRNA, which tells your cells how to make a protein from the coronavirus, allowing it to recognize COVID-19 and protect you from infection. The vaccines also contain lipids, salts, and sugar.

The mRNA is wrapped in tiny lipid (oil) bubbles to protect the mRNA until your cells can pick it up. The liquid part of the vaccine contains salts and saline (salt water) solution to make the vaccine’s pH and salt levels close to the pH and salt levels in our bodies, and sucrose (sugar) to protect the vaccine’s particles and stop them from sticking together while they’re frozen in transit.

The mRNA vaccines do not contain: pork products, egg, latex, preservatives, blood products, COVID-19 virus cells, mercury, or microchips. The mRNA vaccines do not contain fetal tissue and did not use any cell lines from fetal tissue in the manufacturing of the vaccines.

Full list of ingredients in the Pfizer vaccine, available from the FDA:

Active ingredient

  • nucleoside-modified messenger RNA (modRNA) encoding the viral spike glycoprotein (S) of SARS-CoV-2
  • (4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2- hexyldecanoate)
  • 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide
  • 1,2-distearoylsnglycero-3-phosphocholine
  • cholesterol

Additional ingredients (salts, sugars, buffers)

  • potassium chloride
  • monobasic potassium phosphate
  • sodium chloride
  • dibasic sodium phosphate dihydrate
  • sucrose

Full list of ingredients in the Moderna vaccine, available from the FDA:

Active ingredient

  • nucleoside-modified messenger RNA (modRNA) encoding the viral spike glycoprotein (S) of SARS-CoV-2
  • polyethylene glycol (PEG) 2000 dimyristoyl glycerol (DMG)
  • SM-102
  • 1,2-distearoyl-snglycero-3-phosphocholine
  • cholesterol

Additional ingredients (salts, sugars, buffers)

  • tromethamine
  • tromethamine hydrochloride
  • acetic acid
  • sodium acetate
  • sucrose

The Moderna and Pfizer vaccines continue to offer a high level of protection against COVID-19 and remain essential to stop COVID-19 from spreading. The Centers for Disease Control and Prevention (CDC) reports that the Moderna and Pfizer vaccines appear to be effective against the B.1.1.7 variant, also known as the UK variant, which has been found in Washington state. Studies suggest that antibodies produced by the vaccines also recognize the B.1.351 (South Africa) and P.1 (Brazil) variants. Health experts continue to monitor and research how effective the vaccines will be against variants.

We will prevent the virus from circulating and reduce additional variants by getting vaccinated and continuing to practice other COVID-19 prevention measures including wearing masks, physical distancing from people outside our homes, and washing hands.

Section 3: Vaccine availability

While COVID-19 vaccines are in short supply, they will be made available to certain high-risk groups by the Washington State Department of Health, following recommendations by CDC’s Advisory Committee on Immunization Practices (ACIP). The very limited vaccine in the first weeks will only be given to high risk workers in healthcare settings, people in long-term care facilities, and older adults. As Washington State’s vaccine distribution plan moves forward, all individuals eligible for vaccine in earlier phases of the plan will continue to be eligible.

Gradually, COVID-19 vaccine will be available more widely in 2021. Populations that are at highest risk of either getting COVID-19 or having serious health problems if they are infected will likely be eligible, such as adults with high-risk health conditions, essential workers with higher risk of exposure to COVID-19, and adults 65 or older. Eventually, everyone who wants a vaccine will be able to get one.

COVID-19 vaccines are being distributed to hospitals, pharmacies, high-volume sites, community health centers and other providers. Learn more about where to get vaccinated in King County.

Currently, both vaccine supply and appointments are limited. You may experience delays due to the very high volume of inquiries. This will get easier as vaccine supplies increase and more high-volume sites open.

At this time, no. Because supplies of vaccine are limited and expected to remain limited for weeks to months, vaccination sites will generally have only one vaccine to offer. Different provider sites may have different vaccines as they become available. We anticipate that supply will continue to be limited as eligibility is expanded to other high-risk groups in the coming months. When supplies increase and vaccines are widely available, people should have more options about where they get vaccinated and which vaccine to take.

Public Health – Seattle & King County fully endorses the delivery of vaccine inside of the Washington State phasing guidelines to eligible groups. We're calling on everyone to follow the guidelines and wait to get vaccinated when it's their turn in the effort to save lives. This will help protect people with the highest risk of getting a COVID-19 infection or those who have the highest risk of severe illness or death from COVID-19, and will help ensure that our hospitals have the capacity to provide lifesaving care to everyone who needs it. We do not have a role in monitoring vaccination locations for compliance with phasing guidelines. We expect that the vast majority of vaccine is being delivered to individuals that meet eligibility guidelines.

Vaccine clinical trials for children are currently in early stages and COVID-19 vaccines will not be available until study data shows that the vaccines are safe and effective for children as well as adults. The Pfizer vaccine has been authorized for ages 16 and older and the Moderna vaccine has been authorized for ages 18 and older.

Section 4: What to expect

There is no cost for the COVID-19 vaccine. The vaccine will be covered by Medicare, Medicaid and most private insurance, and the cost of the vaccine will be covered for people who are uninsured.

There may be a copay or office visit fee, depending on your insurance plan or the doctor you see.

Public Health – Seattle & King County is also planning opportunities for free vaccination clinics. Equitable distribution is a priority for these clinics. More information will be shared broadly when we enter this phase of distribution.

The COVID-19 vaccines currently available require two doses, one shot to start building protection and a second shot to maximize and complete the protection.

Your second shot should be given 21 or 28 days after the first one, depending on the type of vaccine. You will need to get the same type of vaccine for both shots. When you get your first shot, your vaccination provider will give you information about when to get the second dose.

The recommended schedule for getting your second dose is 21 days after the first dose for the Pfizer vaccine and 28 days after the first dose for the Moderna vaccine. It’s best to receive the second dose as close to that timeline as possible, but you may receive the second dose up to 6 weeks (42 days) after the first dose. It’s not yet known how effective mRNA COVID-19 vaccines are when the second dose is received more than 42 days after the first dose. However, you may still receive your second dose after 42 days, and do not need to restart the vaccine series.

Some people might have some symptoms like headache, a sore arm, fatigue, fever, or muscle aches for a few days after getting the shot. These symptoms are more common after the second dose of vaccine. These are all signs that the body’s immune system is building up protection. This is normal and can also be seen after other commonly used vaccines.

Anaphylaxis—a severe allergic reaction—is extremely rare after getting the COVID-19 vaccine. Everyone who experienced anaphylaxis after COVID-19 vaccination has fully recovered, based on available information, and no deaths have occurred. The risk of severe illness and death from COVID-19 is far greater than the risk of experiencing anaphylaxis or another severe reaction after vaccination.

The CDC has published reports with additional information on anaphylaxis and other allergic reactions to the vaccines:

Most people who experienced anaphylaxis developed symptoms within 15 minutes of getting the vaccine. All these patients were treated with epinephrine immediately after showing symptoms.

All vaccination locations have medical professionals trained to identify and respond to anaphylaxis. They monitor everyone who receives a COVID-19 vaccine for 15 minutes following the vaccination so they can assist if needed.

You may return to work and not quarantine within a few days of vaccine administration, IF:

  • You have not been in contact with someone with COVID-19 AND
  • You feel well enough and are willing to perform normal activities such as work AND
  • You do not have a fever AND
  • Signs and symptoms are limited only to those observed following COVID-19 vaccination (see list of symptoms, including pain, swelling, tiredness, chills, headache) AND
  • You do not have other signs and symptoms of COVID-19, such as cough, shortness of breath, sore throat, or change in smell or taste.

Additional resources:
CDC: Post Vaccine Considerations for Healthcare Personnel
CDC: Post Vaccine Considerations for Residents of Long-Term Care

The CDC has created V-safe, a free, smartphone-based tool that uses text messaging and web surveys to provide personalized health check-ins after you receive a COVID-19 vaccination. V-safe also reminds you to get your second dose. We encourage you to participate in V-safe. Learn more at

The vaccine will give you a high level of protection against the infection, but the protection is not 100%. We don't yet know how well the vaccine prevents people from spreading the virus. It’s possible that someone who is vaccinated may get infected again and even if they don’t get sick, it’s possible that they could still spread COVID-19 to others. Studies are in progress to answer this question.

At this time, people who get vaccinated should continue to follow current public health guidance. Over time, as more people in the community are vaccinated, we may be able to adjust other COVID-19 prevention measures that are currently needed.

COVID-19 vaccines will not cause you to test positive on viral tests used to detect current infection.

Antibody tests look for antibodies in the blood that indicate if a person has been infected with a virus or bacteria. Antibodies are also produced when someone receives an effective vaccine. If your body develops an immune response to the COVID-19 vaccine, it is possible that you may test positive on some antibody tests for COVID-19.

People who have had COVID-19 may still benefit from getting vaccinated. According to the CDC, vaccination should be offered to people regardless if they have had COVID-19.

Current evidence suggests that reinfection with COVID-19 is not common in the 90 days after infection. People who had COVID-19 in the last 90 days may choose to delay vaccination until near the end of this period, if desired. Testing for prior infection solely for the purpose of vaccine decision-making is not recommended.

It will be your choice whether to get the vaccine for COVID-19. Washington State is not currently considering any mandates for the vaccine, but employers could require it. Public Health recommends COVID-19 vaccination as is a safe, effective, and important way to prevent COVID-19, decrease illnesses, hospitalizations, and deaths due to COVID-19, and help to stop the current pandemic.

Currently, the U.S. government is not requiring COVID-19 vaccination for visitors to the United States, or for U.S. residents traveling to other countries when they reenter the U.S. However, individual airlines may require travelers to provide proof of vaccination when flying on their airline. Please check all travel safety requirements with your airline before arranging travel.

As vaccine distribution continues, other countries may require proof of vaccination in the future before allowing travelers to enter, but no countries have established vaccination requirements at this time.

The CDC recommends that travelers avoid all nonessential travel, and has shared guidance about domestic travel in the U.S. You can find answers from the CDC's frequently asked questions about travel.

Safe and effective vaccines against COVID-19 are a major breakthrough in preventing COVID-19 and eventually ending the COVID-19 pandemic. But vaccines alone won’t end the pandemic right away. At this time, vaccination needs to be used in combination with other prevention methods.

Even after a vaccine is available, stopping the pandemic will continue to require everyone – even if vaccinated – to continue to follow current guidance to protect themselves and others. For several months, we will need to continue wearing a mask, staying at least 6 feet away from others, limiting activities outside the home and avoiding crowds, washing hands often, following CDC travel guidance, and following quarantine guidance after an exposure to someone with COVID-19.