iii. Vaccine General Information

III. COVID-19 Vaccine FAQs

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iii. Vaccine General Information


Vaccines work with your immune system so your body will be ready to fight the virus if you are exposed. Two vaccines, both based on messenger RNA (mRNA), have been authorized for emergency use. On February 27, 2021, Johnson and Johnson was approved by the FDA for emergency authorization of their single-dose vaccine, which is based on adding a gene from the COVID-19 spike protein to a virus that carries the common cold. See the links below to understand how these vaccines and others work. Once you are vaccinated, it will help your body develop immunity to COVID-19 virus without you having to get sick first.

Visit the pages below to learn more:


Herd immunity happens when so many people in a community become immune to an infectious disease that it stops the disease from spreading. No modern diseases have achieved herd immunity without a vaccine.

Herd immunity is an important way for the rest of us to protect people who cannot be vaccinated, such as newborns or those who have compromised immune systems.

Like all other modern epidemics which are under control, we look to the development of a COVID-19 vaccine to provide herd immunity.

Experts estimate that in the U.S., 70% of the population would need to have COVID-19 antibodies in order to reach herd immunity. The emergence of some new variants of the coronavirus, which are more transmissible than the original virus may mean that 80-85% of the U.S. population needs to be vaccinated to reach herd immunity. Estimates  in early fall of 2021 were that only about 11.5% of Orange County have been exposed to COVID-19. Current estimates, in the second week of February, are that, for the U.S., the combined effects of past infections and vaccinations has resulted in just over 30% of the population having some degree of immunity.

Visit the pages below to learn more:

  1. World Health Organization’s COVID-19: Herd immunity, lockdowns and COVID-19
  2. Mayo Clinic’s Herd Immunity and COVID-19: What you need to know
  3. Herd Immunity Op-Ed
  4. Path to Herd Immunity

COVID-19 vaccines are being carefully tested in clinical trials. A vaccine will only be approved if it makes it much less likely that someone who is vaccinated will get COVID-19 illness, particularly severe illness, when exposed to the virus. The first two vaccines authorized by the FDA for emergency use have shown 94-95% effectiveness in reducing illness from COVID-19. Pfizer, Moderna and Johnson and Johnson vaccines all prevented hospitalization and death in persons vaccinated during clinical trials.

Based on what we know about the current vaccines, it is clear that they keep you from getting seriously ill even if you do get COVID-19. Recent research also suggests that vaccines are 60-80%  effective in protecting you from getting infected in the first place. This means that you are less likely to be able to transmit the virus to others. Getting the vaccine will also be a safer way for you to protect your family and those around you, especially people who are unable to get the vaccine due to medical reasons.

Visit CDC’s Benefits of Getting a COVID-19 Vaccine to learn more.


Several companies are developing vaccines that work against SARS-CoV-2, the virus that causes COVID-19. Two have been tested in large-scale clinical trials and have or are likely to be authorized for use in 2020 by the FDA (Food and Drug Administration). They include:

Pfizer-BioNTech mRNA vaccine Ages12 and above

  • Granted Emergency Use Authorization (EUA) on 12/11/2020
  • Large-scale trial (44,000 participants) showed 95% protection from disease
  • Two-dose vaccine, requires ultra-cold storage (–70 Celsius)

Moderna mRNA vaccine Ages 18 and above

  • Emergency Use Authorization (EUA) granted 12/18/2020
  • Large-scale trial (30,000 participants) showed 94% protection
  • Two-dose vaccine, requires standard cold storage (–20 Celsius)

Johnson and Johnson single-dose vaccine Ages 18 and above

  • Emergency Use Authorization (EUA) granted on  2/27/21.
  • Vaccine can be stored in normal-use refrigerators.
  • Distribution began week of 3/1/21.

Many types of COVID-19 vaccines are in development. The Pfizer and Moderna vaccines are both made with mRNA, or messenger ribonucleic acid, that can instruct your body to make a specific protein (the spike protein) found on the surface of the SARS-CoV-2 virus.

When your body makes this viral protein, it is recognized as not human, and your body develops antibodies to it. These antibodies protect you if you encounter the virus later.

After making the protein, your body destroys the mRNA, which does not mix with your genetic code or stay in the body. mRNA vaccines have been used effectively in the past for flu, rabies, CMV (cytomegalovirus) and Zika viruses.