Child giving her teddy bear a shot

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 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. Approval is only given if the vaccine is shown to be safe and the reviewers conclude that the benefits outweigh any potential risks.

Many thousands of children and adults of different ages and races volunteered for clinical trials to test the COVID-19 vaccines, and over 72% of Californians have completed their primary series. The FDA and U.S. Centers for Disease Control and Prevention (CDC) continue to track side effects and watch for any safety concerns.

What’s in the COVID-19 vaccines?

The Moderna and Pfizer 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.  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.

Who can get a COVID-19 vaccine?

People 6 months and older can get a COVID-19 vaccine.  The CDC recommends COVID-19 vaccines for everyone aged 6 months and older.

What COVID-19 vaccines are available?

•    The FDA has given full approval for the Pfizer and Moderna vaccines for people 6 months and older.  Both Pfizer and Moderna have been approved for young children.
•    The FDA has given emergency use authorization for the Novavax COVID-19 vaccine. People 12 years and older can get two doses of Novavax spaced three weeks apart as a primary series and a Novavax booster six months after. Novavax offers an alternative to the mRNA vaccines for people who cannot or prefer not to get an mRNA vaccine.
•    The FDA has limited the use of the Johnson & Johnson COVID-19 vaccine because of potential health risks. In most cases, another vaccine is preferred.

What is a bivalent vaccine? 

Bivalent COVID-19 vaccines have mRNA from the original COVID-19 strain and mRNA from the omicron variants BA.4 and BA.5. The updated bivalent booster targets both the original strain and newer omicron strains. The updated booster is broadly protective against COVID-19 because the original (monovalent) COVID-19 boosters only target the original strain of the virus. The bivalent boosters offer better protection against the types of COVID-19 you’re most likely to be exposed to now and in the near future. All currently available mRNA vaccines are bivalent vaccines. 

Are the COVID-19 vaccines effective?

Yes. The vaccines produce a strong immune response in adults and young children and protect against severe disease. While certain virus strains that cause COVID-19 spread easily and may lead to breakthrough cases,  vaccines continue to protect people from becoming very sick, being hospitalized, or dying from COVID-19. Even with new strains, getting vaccinated is a safe and reliable way to protect yourself from COVID-19. The virus may change again over time creating new variants. Scientists will continue to monitor these variants.

When are people considered “up-to-date” on their COVID-19 vaccines? 

Consult with a health care provider about your/your child’s vaccine status, and check the most up-to-date Centers for Disease Control and Prevention (CDC) guidance. As of August 2023, the CDC recommends: 

  • For children 6 months to 5 years old: 
    • Children 6 months to 4 years old receiving the Pfizer vaccine: have three doses, including one or more updated vaccines. 
    • Children 5 years old receiving the Pfizer vaccine: have one updated vaccine. 
    • Children 6 months to 5 years old receiving the Moderna vaccine: have two doses, including one or more updated doses. 
  • For children and adults 6 years old and older:  
    • Have one updated Pfizer or Moderna vaccine (or have completed your Novavax vaccine doses).  
    • People 65 years old and older and people who are moderately or severely immunocompromised can receive another bivalent Moderna or Pfizer vaccine for extra protection. 

COVID-19 vaccine recommendations will be updated as needed. 

How long do COVID-19 boosters protect people?

The COVID-19 boosters offer the best protection against getting sick with COVID-19 in the months following the shot. Two weeks after getting the vaccine the risk of getting sick is low and the risk gradually goes up over the first six months. However, the vaccine and boosters will continue to provide long-term protection against severe disease, hospitalization, and death.

Are there side effects?

There can be side effects. 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. These side effects usually clear up within a day or two.  Keep in mind, the side effects from the vaccine are generally much milder than getting COVID-19.

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. 

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. Studies show that people who had COVID-19 and got the vaccine had a stronger immune response than those who had COVID-19 and did not get the vaccine. 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. 

Do people still need to wear a mask after they've had the vaccine?

It depends on your personal risk and your community levels of COVID-19. Follow public health recommendations for wearing a mask.  This is especially important if:
•    local COVID-19 hospital admissions levels are high, or
•    your child care program is experiencing a COVID-19 outbreak, or
•    you are at risk for severe disease or are immunocompromised.
Check the CDC website for information about community levels of COVID-19 in your county.

Where can people get COVID-19 vaccines?

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.  Check with your local public health department or primary care provider about where the vaccine is be available in your location.  Parents or legal guardians need to provide signed consent for their child to receive the vaccine.

What does the vaccine cost?

Most health care plans and county health departments provide the vaccine free of charge.

If COVID-19 is less severe in children than adults, why should my child get vaccinated? 

Even though children experience less severe COVID-19 than adults, vaccination will protect your child in the following ways: 

  • They are less likely to get sick with COVID-19.  Not getting sick is even more important for children with underlying health conditions. 
  • They are less likely to get severe illness, be hospitalized, get multisystem inflammatory syndrome (MIS-C), or die if they get COVID-19. 
  • They are less likely to miss school because of being infected with COVID-19. 
  • They are less likely to spread COVID-19 to more vulnerable family, friends, teachers, and classmates. 
  • Your family will be able to travel more freely with less worry about getting COVID-19. 
  • It will be safer for your child to attend important educational, cultural, and social activities and family events. 
  • Getting vaccinated can help stop new variants from emerging 
Will my child be required to get the vaccine for child care entry?  

Each state's government decides which vaccines are required for school or child care entry. At this time, there is no state-wide California requirement for COVID-19 vaccination for child care entry. 

Is the vaccine required for child care workers?

Getting a COVID-19 vaccine is voluntary, but some employers require vaccination for their workers. Some public venues may also require proof of vaccination for entry.

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 also help protect the baby from COVID-19. Pregnant people should talk to their health care providers about getting the vaccine.

Where can I find more information?  

Centers for Disease Control and Prevention (2023) Stay Up to Date with Vaccines at  

Centers for Disease Control and Prevention (2023) COVID-19 Clinical Guidance at and  

California For All (2023) Vaccines at  

Updated August 2023, UCSF California Childcare Health Program

This article was made possible with funding from the Heising-Simons Foundation.