COVID-19 Vaccine Frequently Asked Questions

How do vaccines work?
Vaccines trigger the body’s natural response to fight illnesses.  Vaccines work by training the immune system to be ready to recognize viruses or bacteria when they enter the body. Then, if a person is exposed to that virus or bacteria, their immune system knows how to respond. The COVID-19 vaccines protect people from getting seriously ill and requiring hospitalization. If a vaccinated person gets COVID-19, they usually have mild symptoms.

Are the COVID-19 vaccines safe?
Yes. The Federal Drug and Administration (FDA) works to make sure that all vaccines are as safe as possible through careful testing. Although COVID-19 vaccines are new, the process for ensuring vaccine safety is not new. All vaccines must meet strict safety standards before being released to the public. Many thousands of adults of different ages and races volunteered for clinical trials to test the COVID-19 vaccines, and over 220 million Americans are fully vaccinated. The FDA and others continue to track side effects and watch for any safety concerns.

What COVID-19 vaccines are available?
The FDA has given full approval for the Pfizer-BioNTech vaccine for people 12 years and older and the Moderna vaccine for people 18 years and older. Children 6 months and older can get the Moderna and Pfizer-BioNTech vaccines under emergency use authorization.

In most situations, the two dose Pfizer-BioNTech or Moderna mRNA vaccines are preferred over the single dose Johnson & Johnson COVID-19 vaccine.

Novavax is the most recent COVID-19 vaccine to get FDA emergency use authorization. People 18 years and older can get two doses of Novavax spaced three weeks apart as a primary series. Novavax offers another option for people who have not gotten their COVID-19 vaccine yet.

Are the COVID-19 vaccines effective against the Omicron variants?
Yes. Omicron variants spread easily and breakthrough cases occur.  However, vaccines continue to protect people from becoming very sick, being hospitalized, or dying from COVID-19. The virus may change again over time creating new variants, and scientists will continue to monitor and study these variants. Despite the variants, getting vaccinated is still the best strategy against COVID-19.

What’s in the COVID-19 vaccines?
The Moderna and Pfizer-BioNTech vaccines have mRNA, genetic material that our cells use to make spike proteins. Then our bodies respond by making antibodies. The mRNA COVID-19 vaccines do not have preservatives, which is why they must stay frozen until they are ready to use. The Johnson & Johnson vaccine has a modified adenovirus that delivers instructions for the body to make antibodies. Novavax is a protein-based vaccine. Novavax stimulates an immune response using a technique that is well-known and established. It is similar to other common vaccines you may have had such as seasonal flu, pertussis, and hepatitis B.  Vaccines may also have lipids, salts, sugars, acids, and acid stabilizers to help keep them stable to deliver the active ingredients. Vaccines do not contain ingredients that are poisonous or harmful.

Will mRNA change my DNA?
No. When the mRNA enters a cell it provides instructions to make a spike protein similar to that of the SARS-CoV-2 virus (the virus that causes COVID-19). Your body responds by making antibodies to recognize the spike protein. After you have the spike protein in your body, the mRNA is destroyed. It will not mix with your DNA.

Are there side effects?
Yes. The most common side effect is pain in the arm where you get the vaccine. Some people also have one or more of these symptoms: tiredness, headache, muscle pain, chills, joint pain, and fever. Another side effect is swollen lymph nodes in the neck or under the arm where the vaccine was given. These are all signs of the body’s immune system working! More people had these side effects after the second dose than after the first dose. A very small number of the many people vaccinated have had more serious side effects such as a severe allergic reaction.  Talk to your health care provider if you have had a severe allergic reaction to other vaccines or any ingredients in the COVID-19 vaccines. Your health care provider can help you decide if it is safe for you to receive the COVID-19 vaccine.

Should people who have already had COVID-19 get the vaccine?
Yes. People who have had COVID-19 may have some immunity against the coronavirus, but this immunity can be weak and may not last long. Most people develop more antibodies to the coronavirus after they are fully vaccinated than after getting COVID-19. The vaccine will help your body have a stronger response if you get COVID-19 again. People with COVID-19 should wait until they are no longer infected, and check with their health care provider before getting the vaccine.

Am I protected as soon as I receive the vaccine?
No.  It takes time to build immunity in response to the vaccines. The Centers for Disease Control (CDC) considers people fully vaccinated against COVID-19 when at least two weeks have passed since their final dose of the recommended schedule for the vaccine.

Do I still need to wear a mask after I’ve had the vaccine?
It depends. The vaccine is an important way to stay safe, but when community transmission is high or if you are at risk for severe disease or are immunocompromised, continue to follow public health recommendations including wearing masks, maintaining physical distance, avoiding crowds, and washing your hands. We are still learning about COVID-19 and its variants, and we don’t know when community spread of the virus will stabilize.

Who can get the vaccine?
People 6 months and older can get a COVID-19 vaccine.

Where can I get a vaccine?
This will vary by county. You can get a vaccine from local pharmacies like CVS or Walgreens, or from your health care provider. Your local health department or school district may also be holding vaccination clinics.  It's best to check with your local public health department or primary care provider about where the vaccine is be available in your location.

What does the vaccine cost?
Most health care plans and county health departments provide the vaccine free of charge.

Is the vaccine required for child care workers?
Getting the COVID-19 vaccine is voluntary. But more and more employers, including California’s public and private K-12 schools and Head Start, are requiring vaccination for their workers. Some people are not eligible to get the vaccine because of their health status and may opt for regular COVID-19 testing instead.

Are young children eligible to get a COVID-19 vaccine?
Yes. The FDA has given emergency use authorization for the Pfizer and Moderna vaccines for children 6 months and older.

When can I get a booster?
Booster shots are now available for everyone 5 years and older.
•    If you got a Moderna or Pfizer vaccine, you can get a booster shot after 5 months.
•    If you got a Johnson & Johnson vaccine, you can get a booster shot after 2 months.
•    People 18 years and older can get a different brand booster shot than they got in their original series. A Pfizer or Moderna booster is strongly advised for those who got the Johnson & Johnson vaccine.

The CDC has also authorized a second booster shot for people over 50 years and older, those who are immune-compromised, and those who got the Johnson & Johnson vaccine. You must have gotten your first booster dose at least 4 months ago to be eligible for the second booster.

Is the vaccine recommended for pregnant people?
Yes. The COVID-19 vaccination is recommended for pregnant people. The CDC recommends that all people who are pregnant, breastfeeding, trying to get pregnant, or might become pregnant in the future be vaccinated for COVID-19. Pregnant people are more likely to get severely ill if they get COVID-19 compared with non-pregnant people. People who contract COVID-19 while pregnant also face a higher risk of having a preterm birth. Getting a COVID-19 vaccine during pregnancy can protect you and your baby. Pregnant people should talk to their health care providers about getting the vaccine.

Once I’m vaccinated, do I need to quarantine if I’m exposed to someone with suspected or confirmed COVID-19?
It depends. If you’ve had a booster or have been recently vaccinated and do not have symptoms, you do not need to quarantine unless you develop symptoms. But you should wear a mask around others for 10 days and test five days after exposure. "Recently vaccinated" means you had the Pfizer or Moderna vaccines within the last six months, or had the J&J within the last two months. If you haven’t had a booster, or were not recently vaccinated, stay home for five days and test on the fifth day. After that, continue to wear a mask around others for five additional days. "Not recently vaccinated" means you had the Pfizer or Moderna vaccines over 6 months ago and have not received a booster, or had a Johnson & Johnson over two months ago and have not received a booster. If you develop symptoms of COVID-19, get a test and stay home.

This collection of questions and answers was made possible with funding from the Heising-Simons Foundation. updated 07/28/2022