COVID-19 Vaccines

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Page last updated on 11/24/2025.

In alignment with leading medical, health, and patient advocacy groups, the County of San Diego affirms that vaccines are not linked to autism. We remain committed to ensuring residents continue to have access to safe and effective vaccines that are based on credible, transparent, and science-based evidence.

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About Vaccines

COVID-19 can cause severe illness or death.You can also continue to have long-term health issues after infection. Getting the COVID-19 vaccine is a safe and dependable way to build immunity to COVID-19 without having to get the illness. Vaccination can reduce your risk of hospitalization or death from COVID-19.

  • Different types of vaccines work in different ways to provide protection.
  • All COVID-19 vaccines prompt our bodies to recognize and help protect us from the virus that causes COVID-19.

None of these vaccines can give you COVID-19.

  • Vaccines do not use any live virus.
  • Vaccines cannot cause infection with the virus that causes COVID-19 or other viruses.
  • Sometimes after vaccination, the process of building immunity can cause symptoms, such as fever. These symptoms are normal signs the body is building immunity.

Currently, there are 2 types of COVID-19 vaccines for use in the United States:

Inside mRNA COVID-19 vaccine
Inside the Novavax Vaccine
  • Protein subunit vaccines (Novavax)

Are there side effects to the COVID-19 vaccine?

  • There may be some mild side effects that go away in a day or two. Side effects are a sign that the vaccine is working. Side effects could include:
    • Pain, redness, or swelling in the arm where you received the vaccine. You can apply a cool, wet washcloth to reduce pain.
    • Mild flu-like symptoms, like tiredness, nausea, muscle aches, chills, headache, or fever. Drink plenty of fluids and rest to feel more comfortable.
  • Severe allergic reactions to vaccines are rare but can happen. 

Are COVID-19 vaccines safe?

Research and development on vaccines like the COVID-19 vaccines have been underway for decades.

All steps were taken to ensure COVID-19 vaccine safety and effectiveness, including:

  • Clinical Trials – All vaccines in the United States must go through three phases of clinical trials to ensure they are safe and effective. With the COVID-19 vaccine, the phases overlapped to speed up the process, but all were completed.
  • Authorization or Approval – Before vaccines are available to people, the U.S. Food and Drug Administration (FDA) reviews data from clinical trials. FDA has determined COVID-19 vaccines meet FDA’s standards and has granted those vaccines Emergency Use Authorizations (EUAs) or full FDA approval.
  • Tracking Safety Using Vaccine Monitoring Systems – Like every vaccine approved for use in the United States, COVID-19 vaccines continue to be monitored for safety and effectiveness. Hundreds of millions of people in the United States have safely received COVID-19 vaccines. CDC and FDA provide updated information on the safety of U.S. authorized or approved COVID-19 vaccines using data from the Vaccine Safety Datalink (VSD), Vaccine Adverse Event Reporting System (VAERS), and other safety monitoring systems.

Learn more about developing COVID-19 vaccines.

Resources

County of San Diego

California Department of Public Health (CDPH)

Centers for Disease Control and Prevention (CDC)

Food and Drug Administration (FDA)